Current IssueEditorial BoardOnline First ArticlesArchive
Current IssueEditorial BoardOnline First ArticlesArchive

Full Research Article

Evaluation of the Effects of Alternative Pasteurization Techniques on the Physicochemical, Microbiological, Rheological and Functional Properties of Camel Milk

A
Ahmed O. Emam1,*
S
Sahar A. Nasser2
1Department of Food Science, Faculty of Agriculture, Ain Shams University, Cairo, Egypt.
2Department of Food and Dairy Science and Technology, Faculty of Agriculture, Damanhur University, Egypt.

ABSTRACT

Background: Camel milk is recognized for its distinctive nutritional and functional properties, particularly in hot and arid regions. Conventional thermal pasteurization, although widely used, can compromise the bioactive components and sensory quality of camel milk due to the sensitivity of its proteins and enzymes to heat. This has driven the search for alternative pasteurization techniques, such as high-pressure processing (HPP) and ultrasonication, which may better preserve the quality parameters crucial for consumer acceptance and industrial demands.

Methods: Fresh camel milk samples were subjected to three pasteurization methods: conventional heat treatment at 72°C for 15 seconds, high-pressure processing (HPP) at 600 MPa/25°C for 5 minutes and ultrasonication using a 20 kHz probe at 750 W for 10 minutes. Physicochemical characteristics (pH, total solids, protein, fat), rheological properties (viscosity, coagulation behavior), color metrics (CIE Lab*, hue angle, browning index), microbiological safety (total viable counts, coliforms, yeasts, molds, spore-formers), antioxidant activity (DPPH assay) and sensory evaluation scores were analyzed following standardized international and local protocols.

Result: High-pressure processing and ultrasonication maintained higher levels of pH, protein and antioxidant activity compared to conventional pasteurization. Microbial loads were significantly reduced by all methods, with HPP and ultrasonication achieving comparable safety to conventional pasteurization. Nonthermal treatments better preserved milk lightness and reduced undesirable browning, leading to improved visual and sensory qualities. Rheological and coagulation properties were closer to raw milk after HPP and ultrasonication, providing advantages for cheese production and overall texture. Sensory evaluations showed that nonthermal methods resulted in higher scores for aroma and overall acceptability. Collectively, the results demonstrate that alternative pasteurization technologies can deliver effective microbial safety while retaining the desirable physicochemical, functional and sensory properties of camel milk, unlike traditional thermal methods.

INTRODUCTION

Camel milk is a nutritionally valuable food source, especially in arid and semi-arid regions, due to its unique composition and potential health benefits. It contains a distinct profile of proteins, vitamins, minerals and bioactive compounds that contribute to its functional and therapeutic properties (Alhassani, 2024). However, the processing of camel milk poses unique challenges compared to bovine milk, primarily due to differences in protein composition and thermal sensitivities. Traditional thermal pasteurization, which involves heating milk to specific temperatures to reduce microbial load, can adversely affect the nutritional quality and sensory characteristics of camel milk (Arain et al., 2024). Camel milk differs markedly from bovine milk in protein composition and fat structure, with the absence of β-lactoglobulin, lower κ-casein concentration and smaller fat globule size presenting unique processing challenges that require adapted pasteurization approaches (Abduku and Eshetu, 2024).
       
The presence of heat-resistant enzymes such as alkaline phosphatase (ALP) in camel milk complicates the applicability of conventional pasteurization indicators, as ALP remains active even at 90°C. Moreover, camel milk proteins, particularly whey proteins, are more susceptible to denaturation during high-temperature treatments, resulting in changes in texture and functionality (Gebrehiwot and Banat, 2025). These limitations have led to increased research interest in alternative pasteurization techniques that can deliver microbial safety with minimal impact on the milk’s bioactive constituents.
       
Emerging non-thermal and mild thermal technologies such as high-pressure processing (HPP), ultrasonication, pulsed electric fields (PEF) and ultraviolet (UV) treatment offer promising alternatives. High-pressure processing uses intense pressure to inactivate microorganisms while preserving heat-sensitive nutrients and enzymes (Pegu and  Arya, 2023). Ultrasonication utilizes high-frequency sound waves to reduce microbial load and enhance milk homogeneity without requiring extensive heating (Chetia et al., 2023). These methods also tend to maintain better the rheological properties and color attributes of camel milk, which are critical quality parameters influencing consumer acceptance (Moatsou, 2024).
       
Rheological properties, encompassing milk viscosity and flow behavior, significantly affect processing performance and final product quality. Traditional pasteurization can alter these properties by causing protein denaturation and aggregation, whereas alternative methods might preserve the milk’s native state more effectively. Similarly, color parameters such as lightness, redness and yellowness serve as indicators of quality changes during processing and storage and can be better retained with non-thermal treatments (Al-Thaibani  et al., 2024).
       
This study aims to comparatively evaluate the effects of selected alternative pasteurization methods, including high-pressure processing and ultrasonication, against conventional thermal pasteurization on the physicochemical, microbiological, rheological and color characteristics of camel milk. The objective is to identify processing approaches that optimize microbial safety without compromising the nutritional and sensory quality of this valuable dairy product.

MATERIALS AND METHODS

Sample collection and pasteurization
 
Fresh raw camel milk was collected from ALTaleb farm, Riyadh, KSA, under hygienic conditions and transported under refrigerated conditions (4°C) to the pilot plant of Modern Foods Company for food industries during the period from 25/6/2025 to 12/7/2025. Traditional thermal pasteurization was performed using a lab-scale pasteurizer (Microthermics, USA), where milk was heated to 72°C for 15 seconds, followed by rapid cooling to 4°C (Codex Alimentarius,  2018). High-pressure processing was conducted using a Hiperbaric 525 HPP unit (Hiperbaric, Burgos, Spain) with 35 L vessel capacity, applying 600 MPa at 25°C for 5 min (maximum pressure: 600 MPa/87,000 psi; throughput: ~260 kg/h). Ultrasonication was applied for 10 min. using a VCX 750 Ultrasonic Processor (Sonics and Materials Inc., USA) equipped with CV334 piezoelectric converter and 13 mm (½”) titanium probe (20 kHz frequency, 750 W net power output, amplitude 20-100%, temperature-controlled ice bath). In all treatments, milk volume was checked and readjusted to original levels pre-analysis to eliminate evaporation bias during thermal processing (Aljasass et al., 2023).
 
Physicochemical analysis
 
The pH of milk samples was measured using a calibrated digital pH meter (Hanna Instruments). Total solids, fat and protein content were determined according to AOAC standard methods (AOAC, 2019).
       
Viscosity and rheological properties were measured using a Brookfield rotational viscometer equipped with an appropriate spindle for low-viscosity dairy products at 25°C. The shear rate was gradually increased from 1 to 100 s-1 and then decreased back to 1 s-1 to obtain flow curves for each sample. Shear stress and apparent viscosity values were recorded at each shear rate and the flow behavior index and consistency coefficient were calculated by fitting the data to the power-law model. These measurements were used to compare the impact of different pasteurization treatments on the flow behavior and texture-related properties of camel milk (Atwaa et al., 2023). Color parameters were recorded using a Minolta CR-400 colorimeter and expressed in CIE Lab* to quantify lightness, redness and yellowness, respectively (De Vela and Elepaño, 2024). The Hue angle (h°) and Browning Index (BI) were calculated using the formulas described by Tobolková and Durec (2023).
 
Microbiological analysis
 
Total viable counts (TVC), coliform counts and yeast and mold counts were performed using Plate Count Agar (PCA), MacConkey agar and Potato Dextrose Agar (PDA), respectively, according to ISO 707:2008 (Milk and milk products, Guidance on sampling) and ISO 6611-1:2014 (Milk and milk products,  Enumeration of colony-forming units of yeasts and/or moulds). Samples were incubated under appropriate conditions (TVC: 30°C/72 h; coliforms: 37°C/24 h; yeasts/molds: 25°C/5 days) and colonies were enumerated as log CFU/mL (Arain et al., 2024). Enumeration of spore-forming bacteria was performed by heat-treating samples at 80°C for 12 minutes to select heat-resistant spores, followed by plating on PCA and incubation at 30-35°C for 48 h (mesophilic spore count), following Standard Methods for the Examination of Dairy Products (Sun et al., 2024).
 
Rennet coagulation ability
 
The coagulation properties of camel milk samples were assessed using a rennet coagulation test. Rennet (Chy-Max M, Chr. Hansen, Denmark; 1000 IMCU/mL) was added at 50 µL/L to milk samples (pH 6.6, 10% w/v solids) incubated at 37°C. Clotting time (r), curd firmness and coagulation rate were determined using a TA.XT Plus Texture Analyzer (Stable Micro Systems, UK) equipped with a 5 kg load cell and cylindrical probe (P/5S). Clotting time was recorded as time from rennet addition to visible gel formation (r = 45-62 min). Curd firmness measured by penetration test (10 mm distance, 1 mm/s speed, 5 g trigger force), recording maximum force as peak firmness. Coagulation rate calculated as firmness increase/min during 30-60 min post-rennet (0.10-0.19 mm/min). Measurements in triplicate following Mbye et al., (2022).
 
Antioxidant activity
 
Antioxidant activity was measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, a widely accepted and simple method to evaluate the free radical scavenging capacity of compounds. In this assay, 0.5 mL of milk sample was mixed with 3 mL of absolute ethanol and then 0.3 mL of 0.5 mM DPPH solution in ethanol was added. The mixture was incubated in the dark for 30 minutes at room temperature. The reduction in purple color intensity caused by the DPPH radical was measured spectrophotometrically at 517 nm. The decrease in absorbance indicates the ability of antioxidants in the sample to donate hydrogen to neutralize free radicals, resulting in discoloration from purple to yellow (Harizi et al., 2023; Danielyan et al., 2025).
 
Statistical analysis
 
All experiments were conducted in triplicate and data were analyzed by one-way ANOVA followed by Duncan’s multiple range test for multiple comparisons using SPSS version 25. Differences were considered significant at p<0.05. Duncan’s test was selected due to its superior power for detecting differences among multiple treatment means in agricultural and food science experiments (Field, 2024; Krstović et al., 2025).

RESULTS AND DISCUSSION

Physicochemical properties of camel milk
 
Table 1 demonstrates the impact of various pasteurization treatments, including conventional, high-pressure processing (HPP) and ultrasonication, on the physicochemical properties of camel milk. The pH values showed a slight but significant reduction following conventional pasteurization, while HPP maintained higher pH levels, consistent with recent evidence that pressure treatments decrease titratable acidity and enhance pH by promoting colloidal calcium phosphate dissolution and micelle disaggregation (Mbye et al., 2021; Mazumder, 2024). Total solids and macronutrient contents showed variation between treatments. Notably, HPP-treated samples retained significantly higher protein (3.46±0.07% vs. 3.38 ±0.12%, p<0.05) and fat (3.92±0.09% vs. 3.84±0.17%, p<0.05) content compared to conventional pasteurization, with corresponding higher total solids content (12.71± 0.13% vs. 12.27±0.09%). This finding is attributed to limited protein denaturation during high-pressure processing and improved retention of milk constituents (Gebrehiwot and Banat, 2025). Ultrasonication showed intermediate preservation of compositional parameters (protein: 3.43± 0.11%, fat: 3.89±0.08%, total solids: 12.64±0.16%), which were not significantly different from HPP or raw milk, aligning with evidence that such nonthermal technologies maintain nutritional value and bioactive components while improving microbial safety (Mudgil  et al., 2022). No substantial differences in density were observed across treatments, suggesting that the physical structure is maintained by all methods. These findings collectively confirm that alternative pasteurization methods like high-pressure processing and ultrasonication preserve the physicochemical integrity of camel milk more effectively than conventional thermal treatment (Hou et al., 2024).

Table 1: Physicochemical properties of camel milk after different pasteurization treatments.


 
Color characterization of camel milk
 
The results presented in Table 2 illustrate that pasteurization treatments significantly affected the color parameters of camel milk, including L* (lightness), a* (red-green axis), b* (yellow-blue axis), hue angle and browning index. Conventional pasteurization caused a noticeable reduction in L* values, indicating a darker appearance compared to raw and non-thermally processed samples. This decrease in lightness is attributed to the disruption and aggregation of casein micelles under heat treatment, which increases light absorption and reduces reflectivity (Wang et al., 2024). High-pressure processing and ultrasonication maintained higher L* values similar to raw milk, confirming their protective effect on the native microstructure and color of camel milk (Mazumder, 2024).

Table 2: Color parameters of camel milk after different pasteurization treatments.



The a* and b* values exhibited significant shifts upon thermal processing. The a* parameter increased in conventionally pasteurized milk, suggesting a shift towards red tones commonly associated with Maillard reactions and pigment degradation during heating (Zhao et al., 2023). Conversely, ultrasonication and high-pressure processing minimized these color changes, preserving a more natural and appealing hue. The b* values displayed slight variation across treatments, indicating a mild impact on the yellow-blue balance, as previously observed in studies on UHT and HTST processing of various milks (Al-Zoreky, 2024).

Both hue angle and browning index values demonstrated that thermal pasteurization induced substantially greater browning and chromatic shifts compared to non-thermal alternatives. The browning index (BI) was markedly elevated in conventionally pasteurized samples (22.47±0.61a), reflecting accelerated non-enzymatic browning via Maillard reactions requiring temperatures >60°C for significant lactose-lysine interactions (Pandiselvam et al., 2023; Rabbani et al., 2025).
       
Paradoxically, modest but statistically significant BI elevations occurred in HPP (19.76±0.46b; Δ+7.9%) and ultrasonication (19.23±0.55b; Δ+5.0%) relative to raw milk (18.31±0.52c), despite their purported non-thermal nature. These derive from HPP-induced protein oxidation via pressure-disrupted hydrophobic interactions (Gebrehiwot and Banat, 2025), ultrasonication-generated hydroxyl radicals from acoustic cavitation causing localized oxidation (Thi et al., 2020) and reversible casein aggregation altering light scattering properties (Li et al., 2023).
       
HPP/US induced merely 5-8% BI escalation versus 22.7% for thermal treatment (p<0.01), affirming superior color retention. Hue angle plummeted in thermal samples (86.53±0.39°c) versus raw milk (105.56±0.41°a), while HPP (99.12±0.42°b) and ultrasonication (102.34±0.50°ab) preserved native chromaticity (p<0.05).
       
Taken together, these results demonstrate that nonthermal processing technologies such as high-pressure processing and ultrasonication can maintain the desirable color and appearance of camel milk, aligning with recent advances advocating nontraditional techniques to preserve both sensory and nutritional attributes in dairy science (Kapoor et al., 2024; Mazumder, 2024).
 
Microbiological properties of camel milk
 
The microbiological analysis presented in Table 3 clearly demonstrates that all pasteurization methods significantly reduced the microbial load in camel milk compared to raw milk, confirming their effectiveness in enhancing product safety. Conventional pasteurization exhibited the greatest reduction in total viable counts (TVC), coliforms, yeasts, molds and spore-forming bacteria, consistent with traditional thermal treatments known for robust microbial inactivation (Osaili et al., 2025).

Table 3: Microbiological properties of camel milk after different pasteurization treatments.


       
High-pressure processing (HPP) and ultrasonication also substantially decreased microbial populations, albeit with slightly higher residual counts than conventional pasteurization. This aligns with previous studies indicating that HPP disrupts microbial cell membranes through pressure-induced damage while preserving thermal-sensitive nutrients (Mbye et al., 2025). Similarly, ultrasonication inactivates microorganisms by cavitation effects without extensive heating, offering a balance between microbial safety and retention of quality attributes. Recent studies have demonstrated that camel milk possesses intrinsic antimicrobial properties that are resistant to pasteurization, with pasteurized camel milk retaining inhibitory activity against Cronobacter sakazakii and other pathogens even after thermal treatment (Drici et al., 2025).
       
Interestingly, spore-forming bacteria counts were reduced across treatments but remained detectable, which is a recognized challenge due to their intrinsic resistance to both heat and pressure. These findings emphasize the need for combined or hurdle technologies to ensure complete spore inactivation in camel milk processing (Safwa et al., 2024).
       
Overall, the data validate the potential of alternative, non-thermal pasteurization techniques to provide effective microbial control comparable to traditional pasteurization while also preserving physicochemical and sensory characteristics, supporting their growing adoption in high-quality dairy product manufacturing (Mazumder, 2024; Osaili et al., 2025).
 
Rennet coagulation ability of camel milk
 
The rennet coagulation ability of camel milk, as presented in Table 4, reveals significant differences among pasteurization treatments. Raw camel milk exhibited the shortest clotting time and the highest curd firmness and coagulation rate, denoting optimal conditions for cheese making, which coincides with previous studies highlighting the inherent coagulation challenges due to camel milk’s unique protein composition (Fguiri et al., 2022).

Table 4: Rennet coagulation ability of camel milk after different pasteurization treatments.


       
Conventional pasteurization significantly prolonged clotting time and reduced curd firmness and coagulation rate, indicating detrimental impacts on casein micelle structure and enzyme activity critical for effective coagulation. Heat treatment is known to induce protein denaturation and whey protein–casein interactions, which disrupt the milk gel network formation (Niu et al., 2025). This finding underscores the challenges in processing camel milk for cheese through traditional high-temperature treatments.
       
Conversely, high-pressure processing and ultrasonication maintained coagulation parameters closer to the raw milk, suggesting preservation of milk’s native protein functionality and micellar integrity. The retention of coagulation ability after these treatments aligns with the principles of nonthermal processing techniques, which minimize protein denaturation and favor better gel formation (Hou et al., 2024). Such preservation is essential for developing improved camel milk cheese products, addressing the technological constraints traditionally associated with this matrix.
       
In summary, these results confirm that alternative pasteurization methods preserve rennet coagulation properties more effectively than conventional thermal pasteurization, thereby offering promising approaches for enhanced camel milk cheese production in the dairy industry (Mazumder, 2024; Arain et al., 2024).
 
Rheological properties of camel milk
 
The rheological measurements of Table 5 showed that all camel milk samples exhibited non-Newtonian, shear-thinning behavior, as indicated by a decrease in apparent viscosity with increasing shear rate (Hernandez et al., 2025). Conventional pasteurization significantly reduced the apparent viscosity compared with raw milk (p<0.05), which may be attributed to heat-induced protein denaturation and partial disruption of the casein micelle structure (Abou-Soliman et al., 2025). In contrast, high-pressure processing and ultrasonication maintained viscosity values closer to those of raw milk, suggesting better preservation of the native protein network and colloidal structure (Mbye et al., 2021; Mudgil et al., 2022).

Table 5: Rheological parameters of camel milk after different pasteurization treatments.


       
The flow behavior index values () obtained from the power-law model confirmed that all samples behaved as pseudoplastic fluids (n<1), while the consistency coefficient (K) was highest in raw and HPP-treated milk and lowest in conventionally pasteurized samples (Al-Thaibani  et al., 2024). These findings indicate that nonthermal treatments are more effective in maintaining the desirable rheological characteristics of camel milk, which are important for processing performance and for the texture of derived products such as fermented milks and cheeses.
 
Antioxidant activity of camel milk
 
The antioxidant activity results displayed in Table 6 demonstrate that raw camel milk exhibits the highest DPPH radical scavenging capacity, reflecting its rich content of natural antioxidants such as vitamins, peptides and bioactive proteins (Mohammed and Alshaibani, 2024). Conventional pasteurization significantly reduced antioxidant activity, likely due to thermal degradation of heat-sensitive antioxidants, including vitamins C and E, as well as partial denaturation of antioxidant proteins (Mudgil et al., 2022; Mazumder, 2024).
       
High-pressure processing and ultrasonication, representing nonthermal or mild thermal treatments, better preserved antioxidant activity, maintaining levels close to those of raw milk. This preservation is attributed to minimal heat exposure and reduced oxidative stress during these treatments, which protect bioactive compounds responsible for the antioxidant potential (Mazumder, 2024; Siddiqui et al., 2024). These findings are consistent with previous studies highlighting the superiority of alternative pasteurization methods in retaining the nutritional and functional quality of camel milk (Mudgil et al., 2022).
       
Overall, the results underscore the advantage of employing nonthermal processing technologies to maintain the intrinsic antioxidant capacity of camel milk, which plays a crucial role in its health benefits and potential therapeutic applications.
 
Sensory evaluation of camel milk
 
The data of Fig 1 indicate that raw camel milk scored the highest in all evaluated sensory attributes, reflecting its superior sensory qualities prior to any processing. Raw milk taste evaluation was excluded due to food safety protocols prohibiting trained panel ingestion of unpasteurized camel milk containing potential zoonotic pathogens (Brucella spp., E. coli O157:H7) per international dairy standards (ISO 22971:2017; EFSA, 2023). Aroma, texture and overall acceptability comprehensively assessed quality without the risk of ingestion. Conventional pasteurization significantly reduced scores across all attributes, particularly in aroma and overall acceptability, which may be due to thermal degradation of volatile aroma compounds and changes in milk’s texture attributes. Such findings align with previous research showing that thermal pasteurization can negatively influence sensory properties due to protein denaturation and Maillard reactions (Zhao et al., 2023).

Fig 1: Sensory evaluation scores of camel milk samples after different pasteurization treatments, excluding the taste score for raw milk.


       
In contrast, high-pressure processing and ultrasonication maintained sensory scores closer to those of raw milk, especially in aroma and overall acceptability. The preservation of these sensory attributes suggests that nonthermal techniques cause minimal alterations to volatile compounds and protein structures, supporting their potential for producing high-quality camel milk with desirable sensory profiles (Mudgil et al., 2022; Mazumder, 2024).
       
Overall, the analysis of Fig 1 demonstrates that alternative processing methods such as high-pressure processing and ultrasonication are promising in preserving the sensory qualities of camel milk, which is crucial for consumer acceptance and product success in the market.

CONCLUSION

In conclusion, this study successfully demonstrated that alternative pasteurization methods such as high-pressure processing and ultrasonication effectively preserve the physicochemical, microbiological, rheological and antioxidant properties of camel milk compared to conventional thermal pasteurization. These non-thermal and mild thermal treatments maintained higher protein integrity, microbial safety, coagulation potential and antioxidant activity, all of which are crucial for producing high-quality camel milk dairy products.
       
The findings highlight the potential application of these emerging technologies to enhance the functional quality and shelf life of camel milk while minimizing the negative impacts associated with heat treatments. This work contributes valuable knowledge toward improving camel milk processing techniques, thereby supporting the development of innovative dairy products tailored to consumer demands and industrial standards.
       
Future research should further explore process optimization, scale-up feasibility and detailed sensory evaluations to fully harness the benefits of alternative pasteurization technologies in camel milk and other dairy matrices.
       
These results provide a robust foundation for advancing camel milk processing, facilitating its integration into value-added products with enhanced nutritional and functional attributes.
 

ACKNOWLEDGEMENT

The authors thank ALTaleb farm (Riyadh, KSA) for providing fresh camel milk samples and Modern Foods Company for food industries for access to pilot plant facilities.
 
Author contributions
 
Ahmed O. Emam: Conceptualization, Methodology, Investigation, Formal analysis, Writing-original draft, Visualization. Sahar A. Nasser: Methodology, Validation, Investigation, Writing-review and editing, Funding acquisition. Both authors contributed to data interpretation and approved the final manuscript.
 
Ethics statement
 
This study involved laboratory analysis of camel milk samples and did not require ethical approval from an institutional review board or animal ethics committee, as no live animals or human subjects were directly involved in experimental procedures beyond standard milk collection under hygienic conditions. All analyses followed international standards for food safety and quality assessment.
 
Funding
 
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
 

CONFLICT OF INTEREST

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

REFERENCES


  1. Abduku, H. and Eshetu, M. (2024). Physico-chemical properties and processing characteristics of camel milk as compared with other dairy species: A review. Asian Journal of Dairy and Food Research. 43(1): 1-7. doi: 10.18805/ajdfr.DRF-303.

  2. Abou-Soliman, N.H.I., Abd-Rabou, H.S., Awad, S. and Ibrahim, A.A. (2025). Impact of thermal treatment on the quality, total antioxidant and antibacterial properties of fermented camel milk. Scientific Reports. 15(1): 8533. https:// doi.org/10.1038/s41598-025-91548-1.

  3. Alhassani, W. E. (2024). Camel milk: Nutritional composition, therapeutic properties and benefits for human health. Open Veterinary Journal. 14(12): 3164-3180. https://doi.org/10.5455/ OVJ.2024.v14.i12.2.

  4. Aljasass, F.M., Hamad, S.H., Aleid, S.M. and El Neshwey, A.A. (2023). Evaluation of high hydrostatic pressure as an alternative method for camel milk preservation. Current Research in Nutrition and Food Science Journal. 11(3): 1153-1165. https://doi.org/10.12944/crnfsj.11.3.20.

  5. Al-Thaibani, A., Mostafa, H., Al Alawi, M., Sboui, A., Hamed, F., Mudgil, P. and Maqsood, S. (2024). Camel milk whey powder formulated using thermal (spray-drying process) and non-thermal (ultrasonication) processing methods: Effect on physicochemical, technological and functional properties. Ultrasonics Sonochemistry. 111: 107097. https://doi.org/10.1016/j.ultsonch.2024.107097.

  6. Al-Zoreky, N.S., Almathen, F.S., Al hashedi, S.A. and AL-Farga, A. (2024). Evaluation of heat stability of camel milk (sterilized and nonevaporated). Journal of Food Quality. 2024(1). https://doi.org/10.1155/2024/5564251.

  7. AOAC. 2019. Official Methods of Analysis of AOAC International. 21st ed. AOAC International, Rockville, MD, USA.

  8. Arain, M.A., Salman, H.M., Ali, M., Khaskheli, G.B., Barham, G.S., Marghazani, I.B. and Ahmed, S. (2024). A review on camel milk composition, techno-functional properties and processing constraints. Food Science of Animal Resources.  44(4): 739-757. https://doi.org/10.5851/kosfa.2023.e18.

  9. Atwaa, E.S.H., Shahein, M.R., Raya-Álvarez, E., Abd El-Sattar, E.S., Hassan, M.A.A., Hashim, M.A., Dahran, N., El- Khadragy, M.F., Agil, A. and Elmahallawy, E.K. (2023). Assessment of the physicochemical and sensory characteristics of fermented camel milk fortified with Cordia myxa and its biological effects against oxidative stress and hyperlipidemia in rats. Frontiers in Nutrition. 10: 1130224. https://doi.org/10.3389/fnut.2023.1130224.

  10. Chetia, J., Panda, T.C., Kumari, S. and Seth, D. (2023). Effect of non-thermal processing on nutritional and functional properties of milk and milk products-A review. Indian Journal of Animal Health. 62(2-Spl). https://doi.org/ 10.36062/ijah.2023.spl.03323

  11. Danielyan, L., Barseghyan, A., Melkumyan, I., Mnatsakanyan, N., Khachanyan, M., Harutyunyan, M. and Hovhannisyan, H. (2025). Transforming ordinary yogurt into functional yogurt using low doses of ethanolic extract of Origanum vulgare L. Functional Food Science. 5(8): 378-392. Online ISSN: 2767- 3146. https://doi.org/10.31989/ffs.v5i8. 1725.

  12. De Vela, R.J.L. and Elepano, A.R. (2024). Drying and color kinetics of decorticated queen pineapple (Ananas comosus Linn.) fiber bleached with hydrogen peroxide solution. Research in Agricultural Engineering. 70(2): 73-81. https://doi.org/10.17221/47/2023-rae.

  13. Drici, H., Khelef, D., Kherouatou, N., Ayachi, A., Benmahdi, L., Hamadache, A., Bouyoucef, A. and Aggad, H. (2025). Heat-stable camel milk-base culture medium efficiency to improve microbiological analysis of raw camel milk.  Asian Journal of Dairy and Food Research. 44(2): 186- 192. doi: 10.18805/ajdfr.DRF-528.

  14. Fguiri, I., Sboui, A., Atigui, M., Arroum, S., Ayeb, N., Dbara, M., Hammadi, M. and Khorchani, T. (2022). Camel milk curd properties: Application of a kiwi juice as a coagulant. Asian Journal of Dairy and Food Research. 42(1): 14- 19. doi: 10.18805/ajdfr.DRF-275.

  15. Field, A. (2024). Discovering Statistics using IBM SPSS Statistics (6th ed.). SAGE Publications.

  16. Gebrehiwot, H.H. and Banat, F. (2025). Powdered camel milk production and changes occurring along the processing steps and storage conditions: A comprehensive review.  Food Chemistry. 493(Pt 4): 146050. https://doi.org/ 10.1016/j.foodchem.2025.146050.

  17. Harizi, N., Zouari, A., Rokbeni, N., Ben Zid, M., M’hiri, N., Salem, A., Ayadi, M.A. and Boudhrioua, N. (2023). Amino acids and protein profiles of defatted camel and cow milk fractions: Correlation with their in vitro antioxidant and antidiabetic activities. Frontiers in Nutrition. 10: 1295878.  https://doi.org/10.3389/fnut.2023.1295878.

  18. Hernandez, A.M., Berto, M.I. and Bianchini, E.M.G. (2025). Viscosity study of maternal and formula milks according to the assessment proposed by the international dysphagia diet standardisation initiative model: A comparison with rheological assessment. CoDAS. 37(3): e20240049. https://doi.org/10.1590/2317-1782/e20240049en.

  19. Hou, W., Ma, X., Yu, Z., Bari, L., Jiang, H., Du, Q., Fan, R., Wang, J., Yang, Y. and Han, R. (2024). Impact of ultrasonic and heat treatments on the physicochemical properties and rennet-induced coagulation characteristics of milk from various species. Ultrasonics Sonochemistry. 111: 107084. https://doi.org/10.1016/j.ultsonch.2024.107084.

  20. Kapoor, R., Karabulut, G., Mundada, V. and Feng, H. (2024). Unraveling the potential of non-thermal ultrasonic contact drying for enhanced functional and structural attributes of pea protein isolates: A comparative study with spray and freeze-drying methods. Food Chemistry. 439: 138137. https://doi.org/10.1016/j.foodchem.2023.138137.

  21. Krstovic, S., Jakšic, S., Miljaniæ, J., Ilièic, B., Živkov, B.M., Guljaš, D., Damjanovic, M. and Jajic, I. (2025). Annual and seasonal variations in aflatoxin M1 in milk: Updated health risk assessment in Serbia. Toxins. 17(11). https://doi.org/ 10.3390/toxins17110544.

  22. Li, X., Qi, B., Zhang, S. and Li, Y. (2023). Effects of homogeneous and ultrasonic treatment on casein/phosphatidylcholine complex-emulsions: Stability and bioactivity insights. Ultrasonics Sonochemistry. 97: 106457. https:/ /doi.org/10.1016/j.ultsonch.2023.106457.

  23. Mazumder, J.A., Ali, A.H. and Banat, F. (2024). Emerging non- thermal treatment approaches for camel milk: A review.  NFS Journal. 37: 100198. https://doi.org/ 10.1016/j.nfs.2024.100198.

  24. Mbye, M., Akram, A., Mohamed, H. and Banat, F. (2025). Impact of ultrasonication and thermal pre-treatments on the quality, proteolysis and bioactive properties of camel milk cheese. Lebensmittel-Wissenschaft Und Technologie [Food Science and Technology]. 232: 118414. https:/ /doi.org/10.1016/j.lwt.2025.118414.

  25. Mbye, M., Ayyash, M., Abu-Jdayil, B. and Kamal-Eldin, A. (2022). The texture of camel milk cheese: Effects of milk composition, coagulants and processing conditions.  Frontiers in Nutrition. 9: 868320. https://doi.org/10.3389/ fnut.2022.868320.

  26. Mbye, M., Mohamed, H., Ramachandran, T., Hamed, F., AlHammadi, A., Kamleh, R. and Kamal-Eldin, A. (2021). Effects of pasteurization and high-pressure processing of camel and bovine cheese quality and proteolysis contribution to camel cheese softness. Frontiers in Nutrition. 8: 642846. https://doi.org/10.3389/fnut.2021.642846.

  27. Moatsou, G. (2024). Emerging technologies for improving properties, shelf life and analysis of dairy products. Foods (Basel, Switzerland). 13(7): 1078. https://doi.org/10.3390/foods 13071078.

  28. Mohammed, A.A. and Alshaibani, N. (2024). Camel milk yield and composition and its adjuvant potential impacts on health of consumers: A review. Indian Journal of Animal Research. 59(2): 177-184. doi: 10.18805/IJAR.BF-1872.

  29. Mudgil, P., Alkaabi, A. and Maqsood, S. (2022). Ultrasonication as a novel processing alternative to pasteurization for camel milk: Effects on microbial load, protein profile and bioactive properties. Journal of Dairy Science. 105(8): 6548-6562. https://doi.org/10.3168/jds.2021-20979.

  30. Niu, Q., Liu, E., Huo, C., Zhang, F., He, R., Yang, J. and Zhao, Z. (2025). Effects of transglutaminase and heat treatment on the structure and gelation properties of camel casein protein. Foods (Basel, Switzerland). 14(9): 1644. https:/ /doi.org/10.3390/foods14091644.

  31. Osaili, T.M., Dhanasekaran, D.K., Hasan, F., Obaid, R.S., Al-Nabulsi, A.A., Olaimat, A.N., Ismail, L.C. et al.  (2025). Changes in microbial safety and quality of high-pressure processed camel milk. Foods (Basel, Switzerland). 14(2): 320. https://doi.org/10.3390/foods14020320.

  32. Pandiselvam, R., Mitharwal, S., Rani, P., Shanker, M. A., Kumar, A., Aslam, R., Barut, Y.T., Kothakota, A., Rustagi, S., Bhati, D., Siddiqui, S. A., Siddiqui, M. W., Ramniwas, S., Aliyeva, A. and Mousavi, K.A. (2023). The influence of non- thermal technologies on color pigments of food materials: An updated review. Current Research in Food Science. 6: 100529. https://doi.org/10.1016/j.crfs.2023. 100529.

  33. Pegu, K. and Arya, S.S. (2023). Non-thermal processing of milk: Principles, mechanisms and effect on milk components. Journal of Agriculture and Food Research. 14: 100730. https://doi.org/10.1016/j.jafr.2023.100730.

  34. Rabbani, A., Ayyash, M., D’Costa, C. D. C., Chen, G., Xu, Y. and Kamal-Eldin, A. (2025). Effect of heat pasteurization and sterilization on milk safety, composition, sensory properties and nutritional quality. Foods (Basel, Switzerland). 14(8): 1342. https://doi.org/10.3390/foods14081342.

  35. Safwa, S.M., Ahmed, T., Talukder, S., Sarkar, A. and Rana, M.R. (2024). Applications of non-thermal technologies in food processing Industries-A review. Journal of Agriculture and Food Research. 18: 100917. https:// doi.org/10.1016/j.jafr.2023.100917.

  36. Siddiqui, S.A., Khan, S., Bahmid, N.A., Nagdalian, A.A., Jafari, S.M. and Castro-Muñoz, R. (2024). Impact of high-pressure processing on the bioactive compounds of milk-A comprehensive review. Journal of Food Science and Technology. 61(9): 1632–1651. https://doi.org/10.1007/ s13197-024-05938-w.

  37. Sun, M., Shao, W., Liu, Z., Ma, X., Chen, H., Zheng, N. and Zhao, Y. (2024). Microbial diversity in camel milk from Xinjiang, China as revealed by metataxonomic analysis. Frontiers in Microbiology. 15: 1367116. https://doi.org/10.3389/ fmicb.2024.1367116.

  38. Thi, H.B.A., Cozzolino, D., Zisu, B. and Chandrapala, J. (2020). Effects of high and low frequency ultrasound on the production of volatile compounds in milk and milk products- A review. The Journal of Dairy Research. 87(4): 501- 512. https://doi.org/10.1017/S0022029920001107.

  39. Tobolková, B. and Durec, J. (2023). Colour descriptors for plant- based milk alternatives discrimination. Journal of Food Science and Technology. 60(9): 2497-2501. https:// doi.org/10.1007/s13197-023-05773-5.

  40. Wang, Y.H., Wuren, T., Zhai, B.T., Er, D. and Yang, H. (2024). Impact of storage conditions on the quality of raw camel milk. Food Science of Animal Resources. 44(6): 1345- 1357. https://doi.org/10.5851/kosfa.2024.e52.

  41. Zhao, X., Guo, Y., Zhang, Y., Pang, X., Wang, Y., Lv, J. and Zhang, S. (2023). Effects of different heat treatments on Maillard reaction products and volatile substances of camel milk. Frontiers in Nutrition. 10: 1072261. https://doi.org/ 10.3389/fnut.2023.1072261.
Published In
Asian Journal of Dairy and Food Research
Article Metrics
Metrics Icon
0
Views
0
Citations
Reviewed By
Share Article
Download Article
In this Article
    Contact us
    Follow us

    Full Research Article

    Evaluation of the Effects of Alternative Pasteurization Techniques on the Physicochemical, Microbiological, Rheological and Functional Properties of Camel Milk

    A
    Ahmed O. Emam1,*
    S
    Sahar A. Nasser2
    1Department of Food Science, Faculty of Agriculture, Ain Shams University, Cairo, Egypt.
    2Department of Food and Dairy Science and Technology, Faculty of Agriculture, Damanhur University, Egypt.

    ABSTRACT

    Background: Camel milk is recognized for its distinctive nutritional and functional properties, particularly in hot and arid regions. Conventional thermal pasteurization, although widely used, can compromise the bioactive components and sensory quality of camel milk due to the sensitivity of its proteins and enzymes to heat. This has driven the search for alternative pasteurization techniques, such as high-pressure processing (HPP) and ultrasonication, which may better preserve the quality parameters crucial for consumer acceptance and industrial demands.

    Methods: Fresh camel milk samples were subjected to three pasteurization methods: conventional heat treatment at 72°C for 15 seconds, high-pressure processing (HPP) at 600 MPa/25°C for 5 minutes and ultrasonication using a 20 kHz probe at 750 W for 10 minutes. Physicochemical characteristics (pH, total solids, protein, fat), rheological properties (viscosity, coagulation behavior), color metrics (CIE Lab*, hue angle, browning index), microbiological safety (total viable counts, coliforms, yeasts, molds, spore-formers), antioxidant activity (DPPH assay) and sensory evaluation scores were analyzed following standardized international and local protocols.

    Result: High-pressure processing and ultrasonication maintained higher levels of pH, protein and antioxidant activity compared to conventional pasteurization. Microbial loads were significantly reduced by all methods, with HPP and ultrasonication achieving comparable safety to conventional pasteurization. Nonthermal treatments better preserved milk lightness and reduced undesirable browning, leading to improved visual and sensory qualities. Rheological and coagulation properties were closer to raw milk after HPP and ultrasonication, providing advantages for cheese production and overall texture. Sensory evaluations showed that nonthermal methods resulted in higher scores for aroma and overall acceptability. Collectively, the results demonstrate that alternative pasteurization technologies can deliver effective microbial safety while retaining the desirable physicochemical, functional and sensory properties of camel milk, unlike traditional thermal methods.

    INTRODUCTION

    Camel milk is a nutritionally valuable food source, especially in arid and semi-arid regions, due to its unique composition and potential health benefits. It contains a distinct profile of proteins, vitamins, minerals and bioactive compounds that contribute to its functional and therapeutic properties (Alhassani, 2024). However, the processing of camel milk poses unique challenges compared to bovine milk, primarily due to differences in protein composition and thermal sensitivities. Traditional thermal pasteurization, which involves heating milk to specific temperatures to reduce microbial load, can adversely affect the nutritional quality and sensory characteristics of camel milk (Arain et al., 2024). Camel milk differs markedly from bovine milk in protein composition and fat structure, with the absence of β-lactoglobulin, lower κ-casein concentration and smaller fat globule size presenting unique processing challenges that require adapted pasteurization approaches (Abduku and Eshetu, 2024).
           
    The presence of heat-resistant enzymes such as alkaline phosphatase (ALP) in camel milk complicates the applicability of conventional pasteurization indicators, as ALP remains active even at 90°C. Moreover, camel milk proteins, particularly whey proteins, are more susceptible to denaturation during high-temperature treatments, resulting in changes in texture and functionality (Gebrehiwot and Banat, 2025). These limitations have led to increased research interest in alternative pasteurization techniques that can deliver microbial safety with minimal impact on the milk’s bioactive constituents.
           
    Emerging non-thermal and mild thermal technologies such as high-pressure processing (HPP), ultrasonication, pulsed electric fields (PEF) and ultraviolet (UV) treatment offer promising alternatives. High-pressure processing uses intense pressure to inactivate microorganisms while preserving heat-sensitive nutrients and enzymes (Pegu and  Arya, 2023). Ultrasonication utilizes high-frequency sound waves to reduce microbial load and enhance milk homogeneity without requiring extensive heating (Chetia et al., 2023). These methods also tend to maintain better the rheological properties and color attributes of camel milk, which are critical quality parameters influencing consumer acceptance (Moatsou, 2024).
           
    Rheological properties, encompassing milk viscosity and flow behavior, significantly affect processing performance and final product quality. Traditional pasteurization can alter these properties by causing protein denaturation and aggregation, whereas alternative methods might preserve the milk’s native state more effectively. Similarly, color parameters such as lightness, redness and yellowness serve as indicators of quality changes during processing and storage and can be better retained with non-thermal treatments (Al-Thaibani  et al., 2024).
           
    This study aims to comparatively evaluate the effects of selected alternative pasteurization methods, including high-pressure processing and ultrasonication, against conventional thermal pasteurization on the physicochemical, microbiological, rheological and color characteristics of camel milk. The objective is to identify processing approaches that optimize microbial safety without compromising the nutritional and sensory quality of this valuable dairy product.

    MATERIALS AND METHODS

    Sample collection and pasteurization
     
    Fresh raw camel milk was collected from ALTaleb farm, Riyadh, KSA, under hygienic conditions and transported under refrigerated conditions (4°C) to the pilot plant of Modern Foods Company for food industries during the period from 25/6/2025 to 12/7/2025. Traditional thermal pasteurization was performed using a lab-scale pasteurizer (Microthermics, USA), where milk was heated to 72°C for 15 seconds, followed by rapid cooling to 4°C (Codex Alimentarius,  2018). High-pressure processing was conducted using a Hiperbaric 525 HPP unit (Hiperbaric, Burgos, Spain) with 35 L vessel capacity, applying 600 MPa at 25°C for 5 min (maximum pressure: 600 MPa/87,000 psi; throughput: ~260 kg/h). Ultrasonication was applied for 10 min. using a VCX 750 Ultrasonic Processor (Sonics and Materials Inc., USA) equipped with CV334 piezoelectric converter and 13 mm (½”) titanium probe (20 kHz frequency, 750 W net power output, amplitude 20-100%, temperature-controlled ice bath). In all treatments, milk volume was checked and readjusted to original levels pre-analysis to eliminate evaporation bias during thermal processing (Aljasass et al., 2023).
     
    Physicochemical analysis
     
    The pH of milk samples was measured using a calibrated digital pH meter (Hanna Instruments). Total solids, fat and protein content were determined according to AOAC standard methods (AOAC, 2019).
           
    Viscosity and rheological properties were measured using a Brookfield rotational viscometer equipped with an appropriate spindle for low-viscosity dairy products at 25°C. The shear rate was gradually increased from 1 to 100 s-1 and then decreased back to 1 s-1 to obtain flow curves for each sample. Shear stress and apparent viscosity values were recorded at each shear rate and the flow behavior index and consistency coefficient were calculated by fitting the data to the power-law model. These measurements were used to compare the impact of different pasteurization treatments on the flow behavior and texture-related properties of camel milk (Atwaa et al., 2023). Color parameters were recorded using a Minolta CR-400 colorimeter and expressed in CIE Lab* to quantify lightness, redness and yellowness, respectively (De Vela and Elepaño, 2024). The Hue angle (h°) and Browning Index (BI) were calculated using the formulas described by Tobolková and Durec (2023).
     
    Microbiological analysis
     
    Total viable counts (TVC), coliform counts and yeast and mold counts were performed using Plate Count Agar (PCA), MacConkey agar and Potato Dextrose Agar (PDA), respectively, according to ISO 707:2008 (Milk and milk products, Guidance on sampling) and ISO 6611-1:2014 (Milk and milk products,  Enumeration of colony-forming units of yeasts and/or moulds). Samples were incubated under appropriate conditions (TVC: 30°C/72 h; coliforms: 37°C/24 h; yeasts/molds: 25°C/5 days) and colonies were enumerated as log CFU/mL (Arain et al., 2024). Enumeration of spore-forming bacteria was performed by heat-treating samples at 80°C for 12 minutes to select heat-resistant spores, followed by plating on PCA and incubation at 30-35°C for 48 h (mesophilic spore count), following Standard Methods for the Examination of Dairy Products (Sun et al., 2024).
     
    Rennet coagulation ability
     
    The coagulation properties of camel milk samples were assessed using a rennet coagulation test. Rennet (Chy-Max M, Chr. Hansen, Denmark; 1000 IMCU/mL) was added at 50 µL/L to milk samples (pH 6.6, 10% w/v solids) incubated at 37°C. Clotting time (r), curd firmness and coagulation rate were determined using a TA.XT Plus Texture Analyzer (Stable Micro Systems, UK) equipped with a 5 kg load cell and cylindrical probe (P/5S). Clotting time was recorded as time from rennet addition to visible gel formation (r = 45-62 min). Curd firmness measured by penetration test (10 mm distance, 1 mm/s speed, 5 g trigger force), recording maximum force as peak firmness. Coagulation rate calculated as firmness increase/min during 30-60 min post-rennet (0.10-0.19 mm/min). Measurements in triplicate following Mbye et al., (2022).
     
    Antioxidant activity
     
    Antioxidant activity was measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, a widely accepted and simple method to evaluate the free radical scavenging capacity of compounds. In this assay, 0.5 mL of milk sample was mixed with 3 mL of absolute ethanol and then 0.3 mL of 0.5 mM DPPH solution in ethanol was added. The mixture was incubated in the dark for 30 minutes at room temperature. The reduction in purple color intensity caused by the DPPH radical was measured spectrophotometrically at 517 nm. The decrease in absorbance indicates the ability of antioxidants in the sample to donate hydrogen to neutralize free radicals, resulting in discoloration from purple to yellow (Harizi et al., 2023; Danielyan et al., 2025).
     
    Statistical analysis
     
    All experiments were conducted in triplicate and data were analyzed by one-way ANOVA followed by Duncan’s multiple range test for multiple comparisons using SPSS version 25. Differences were considered significant at p<0.05. Duncan’s test was selected due to its superior power for detecting differences among multiple treatment means in agricultural and food science experiments (Field, 2024; Krstović et al., 2025).

    RESULTS AND DISCUSSION

    Physicochemical properties of camel milk
     
    Table 1 demonstrates the impact of various pasteurization treatments, including conventional, high-pressure processing (HPP) and ultrasonication, on the physicochemical properties of camel milk. The pH values showed a slight but significant reduction following conventional pasteurization, while HPP maintained higher pH levels, consistent with recent evidence that pressure treatments decrease titratable acidity and enhance pH by promoting colloidal calcium phosphate dissolution and micelle disaggregation (Mbye et al., 2021; Mazumder, 2024). Total solids and macronutrient contents showed variation between treatments. Notably, HPP-treated samples retained significantly higher protein (3.46±0.07% vs. 3.38 ±0.12%, p<0.05) and fat (3.92±0.09% vs. 3.84±0.17%, p<0.05) content compared to conventional pasteurization, with corresponding higher total solids content (12.71± 0.13% vs. 12.27±0.09%). This finding is attributed to limited protein denaturation during high-pressure processing and improved retention of milk constituents (Gebrehiwot and Banat, 2025). Ultrasonication showed intermediate preservation of compositional parameters (protein: 3.43± 0.11%, fat: 3.89±0.08%, total solids: 12.64±0.16%), which were not significantly different from HPP or raw milk, aligning with evidence that such nonthermal technologies maintain nutritional value and bioactive components while improving microbial safety (Mudgil  et al., 2022). No substantial differences in density were observed across treatments, suggesting that the physical structure is maintained by all methods. These findings collectively confirm that alternative pasteurization methods like high-pressure processing and ultrasonication preserve the physicochemical integrity of camel milk more effectively than conventional thermal treatment (Hou et al., 2024).

    Table 1: Physicochemical properties of camel milk after different pasteurization treatments.


     
    Color characterization of camel milk
     
    The results presented in Table 2 illustrate that pasteurization treatments significantly affected the color parameters of camel milk, including L* (lightness), a* (red-green axis), b* (yellow-blue axis), hue angle and browning index. Conventional pasteurization caused a noticeable reduction in L* values, indicating a darker appearance compared to raw and non-thermally processed samples. This decrease in lightness is attributed to the disruption and aggregation of casein micelles under heat treatment, which increases light absorption and reduces reflectivity (Wang et al., 2024). High-pressure processing and ultrasonication maintained higher L* values similar to raw milk, confirming their protective effect on the native microstructure and color of camel milk (Mazumder, 2024).

    Table 2: Color parameters of camel milk after different pasteurization treatments.



    The a* and b* values exhibited significant shifts upon thermal processing. The a* parameter increased in conventionally pasteurized milk, suggesting a shift towards red tones commonly associated with Maillard reactions and pigment degradation during heating (Zhao et al., 2023). Conversely, ultrasonication and high-pressure processing minimized these color changes, preserving a more natural and appealing hue. The b* values displayed slight variation across treatments, indicating a mild impact on the yellow-blue balance, as previously observed in studies on UHT and HTST processing of various milks (Al-Zoreky, 2024).

    Both hue angle and browning index values demonstrated that thermal pasteurization induced substantially greater browning and chromatic shifts compared to non-thermal alternatives. The browning index (BI) was markedly elevated in conventionally pasteurized samples (22.47±0.61a), reflecting accelerated non-enzymatic browning via Maillard reactions requiring temperatures >60°C for significant lactose-lysine interactions (Pandiselvam et al., 2023; Rabbani et al., 2025).
           
    Paradoxically, modest but statistically significant BI elevations occurred in HPP (19.76±0.46b; Δ+7.9%) and ultrasonication (19.23±0.55b; Δ+5.0%) relative to raw milk (18.31±0.52c), despite their purported non-thermal nature. These derive from HPP-induced protein oxidation via pressure-disrupted hydrophobic interactions (Gebrehiwot and Banat, 2025), ultrasonication-generated hydroxyl radicals from acoustic cavitation causing localized oxidation (Thi et al., 2020) and reversible casein aggregation altering light scattering properties (Li et al., 2023).
           
    HPP/US induced merely 5-8% BI escalation versus 22.7% for thermal treatment (p<0.01), affirming superior color retention. Hue angle plummeted in thermal samples (86.53±0.39°c) versus raw milk (105.56±0.41°a), while HPP (99.12±0.42°b) and ultrasonication (102.34±0.50°ab) preserved native chromaticity (p<0.05).
           
    Taken together, these results demonstrate that nonthermal processing technologies such as high-pressure processing and ultrasonication can maintain the desirable color and appearance of camel milk, aligning with recent advances advocating nontraditional techniques to preserve both sensory and nutritional attributes in dairy science (Kapoor et al., 2024; Mazumder, 2024).
     
    Microbiological properties of camel milk
     
    The microbiological analysis presented in Table 3 clearly demonstrates that all pasteurization methods significantly reduced the microbial load in camel milk compared to raw milk, confirming their effectiveness in enhancing product safety. Conventional pasteurization exhibited the greatest reduction in total viable counts (TVC), coliforms, yeasts, molds and spore-forming bacteria, consistent with traditional thermal treatments known for robust microbial inactivation (Osaili et al., 2025).

    Table 3: Microbiological properties of camel milk after different pasteurization treatments.


           
    High-pressure processing (HPP) and ultrasonication also substantially decreased microbial populations, albeit with slightly higher residual counts than conventional pasteurization. This aligns with previous studies indicating that HPP disrupts microbial cell membranes through pressure-induced damage while preserving thermal-sensitive nutrients (Mbye et al., 2025). Similarly, ultrasonication inactivates microorganisms by cavitation effects without extensive heating, offering a balance between microbial safety and retention of quality attributes. Recent studies have demonstrated that camel milk possesses intrinsic antimicrobial properties that are resistant to pasteurization, with pasteurized camel milk retaining inhibitory activity against Cronobacter sakazakii and other pathogens even after thermal treatment (Drici et al., 2025).
           
    Interestingly, spore-forming bacteria counts were reduced across treatments but remained detectable, which is a recognized challenge due to their intrinsic resistance to both heat and pressure. These findings emphasize the need for combined or hurdle technologies to ensure complete spore inactivation in camel milk processing (Safwa et al., 2024).
           
    Overall, the data validate the potential of alternative, non-thermal pasteurization techniques to provide effective microbial control comparable to traditional pasteurization while also preserving physicochemical and sensory characteristics, supporting their growing adoption in high-quality dairy product manufacturing (Mazumder, 2024; Osaili et al., 2025).
     
    Rennet coagulation ability of camel milk
     
    The rennet coagulation ability of camel milk, as presented in Table 4, reveals significant differences among pasteurization treatments. Raw camel milk exhibited the shortest clotting time and the highest curd firmness and coagulation rate, denoting optimal conditions for cheese making, which coincides with previous studies highlighting the inherent coagulation challenges due to camel milk’s unique protein composition (Fguiri et al., 2022).

    Table 4: Rennet coagulation ability of camel milk after different pasteurization treatments.


           
    Conventional pasteurization significantly prolonged clotting time and reduced curd firmness and coagulation rate, indicating detrimental impacts on casein micelle structure and enzyme activity critical for effective coagulation. Heat treatment is known to induce protein denaturation and whey protein–casein interactions, which disrupt the milk gel network formation (Niu et al., 2025). This finding underscores the challenges in processing camel milk for cheese through traditional high-temperature treatments.
           
    Conversely, high-pressure processing and ultrasonication maintained coagulation parameters closer to the raw milk, suggesting preservation of milk’s native protein functionality and micellar integrity. The retention of coagulation ability after these treatments aligns with the principles of nonthermal processing techniques, which minimize protein denaturation and favor better gel formation (Hou et al., 2024). Such preservation is essential for developing improved camel milk cheese products, addressing the technological constraints traditionally associated with this matrix.
           
    In summary, these results confirm that alternative pasteurization methods preserve rennet coagulation properties more effectively than conventional thermal pasteurization, thereby offering promising approaches for enhanced camel milk cheese production in the dairy industry (Mazumder, 2024; Arain et al., 2024).
     
    Rheological properties of camel milk
     
    The rheological measurements of Table 5 showed that all camel milk samples exhibited non-Newtonian, shear-thinning behavior, as indicated by a decrease in apparent viscosity with increasing shear rate (Hernandez et al., 2025). Conventional pasteurization significantly reduced the apparent viscosity compared with raw milk (p<0.05), which may be attributed to heat-induced protein denaturation and partial disruption of the casein micelle structure (Abou-Soliman et al., 2025). In contrast, high-pressure processing and ultrasonication maintained viscosity values closer to those of raw milk, suggesting better preservation of the native protein network and colloidal structure (Mbye et al., 2021; Mudgil et al., 2022).

    Table 5: Rheological parameters of camel milk after different pasteurization treatments.


           
    The flow behavior index values () obtained from the power-law model confirmed that all samples behaved as pseudoplastic fluids (n<1), while the consistency coefficient (K) was highest in raw and HPP-treated milk and lowest in conventionally pasteurized samples (Al-Thaibani  et al., 2024). These findings indicate that nonthermal treatments are more effective in maintaining the desirable rheological characteristics of camel milk, which are important for processing performance and for the texture of derived products such as fermented milks and cheeses.
     
    Antioxidant activity of camel milk
     
    The antioxidant activity results displayed in Table 6 demonstrate that raw camel milk exhibits the highest DPPH radical scavenging capacity, reflecting its rich content of natural antioxidants such as vitamins, peptides and bioactive proteins (Mohammed and Alshaibani, 2024). Conventional pasteurization significantly reduced antioxidant activity, likely due to thermal degradation of heat-sensitive antioxidants, including vitamins C and E, as well as partial denaturation of antioxidant proteins (Mudgil et al., 2022; Mazumder, 2024).
           
    High-pressure processing and ultrasonication, representing nonthermal or mild thermal treatments, better preserved antioxidant activity, maintaining levels close to those of raw milk. This preservation is attributed to minimal heat exposure and reduced oxidative stress during these treatments, which protect bioactive compounds responsible for the antioxidant potential (Mazumder, 2024; Siddiqui et al., 2024). These findings are consistent with previous studies highlighting the superiority of alternative pasteurization methods in retaining the nutritional and functional quality of camel milk (Mudgil et al., 2022).
           
    Overall, the results underscore the advantage of employing nonthermal processing technologies to maintain the intrinsic antioxidant capacity of camel milk, which plays a crucial role in its health benefits and potential therapeutic applications.
     
    Sensory evaluation of camel milk
     
    The data of Fig 1 indicate that raw camel milk scored the highest in all evaluated sensory attributes, reflecting its superior sensory qualities prior to any processing. Raw milk taste evaluation was excluded due to food safety protocols prohibiting trained panel ingestion of unpasteurized camel milk containing potential zoonotic pathogens (Brucella spp., E. coli O157:H7) per international dairy standards (ISO 22971:2017; EFSA, 2023). Aroma, texture and overall acceptability comprehensively assessed quality without the risk of ingestion. Conventional pasteurization significantly reduced scores across all attributes, particularly in aroma and overall acceptability, which may be due to thermal degradation of volatile aroma compounds and changes in milk’s texture attributes. Such findings align with previous research showing that thermal pasteurization can negatively influence sensory properties due to protein denaturation and Maillard reactions (Zhao et al., 2023).

    Fig 1: Sensory evaluation scores of camel milk samples after different pasteurization treatments, excluding the taste score for raw milk.


           
    In contrast, high-pressure processing and ultrasonication maintained sensory scores closer to those of raw milk, especially in aroma and overall acceptability. The preservation of these sensory attributes suggests that nonthermal techniques cause minimal alterations to volatile compounds and protein structures, supporting their potential for producing high-quality camel milk with desirable sensory profiles (Mudgil et al., 2022; Mazumder, 2024).
           
    Overall, the analysis of Fig 1 demonstrates that alternative processing methods such as high-pressure processing and ultrasonication are promising in preserving the sensory qualities of camel milk, which is crucial for consumer acceptance and product success in the market.

    CONCLUSION

    In conclusion, this study successfully demonstrated that alternative pasteurization methods such as high-pressure processing and ultrasonication effectively preserve the physicochemical, microbiological, rheological and antioxidant properties of camel milk compared to conventional thermal pasteurization. These non-thermal and mild thermal treatments maintained higher protein integrity, microbial safety, coagulation potential and antioxidant activity, all of which are crucial for producing high-quality camel milk dairy products.
           
    The findings highlight the potential application of these emerging technologies to enhance the functional quality and shelf life of camel milk while minimizing the negative impacts associated with heat treatments. This work contributes valuable knowledge toward improving camel milk processing techniques, thereby supporting the development of innovative dairy products tailored to consumer demands and industrial standards.
           
    Future research should further explore process optimization, scale-up feasibility and detailed sensory evaluations to fully harness the benefits of alternative pasteurization technologies in camel milk and other dairy matrices.
           
    These results provide a robust foundation for advancing camel milk processing, facilitating its integration into value-added products with enhanced nutritional and functional attributes.
     

    ACKNOWLEDGEMENT

    The authors thank ALTaleb farm (Riyadh, KSA) for providing fresh camel milk samples and Modern Foods Company for food industries for access to pilot plant facilities.
     
    Author contributions
     
    Ahmed O. Emam: Conceptualization, Methodology, Investigation, Formal analysis, Writing-original draft, Visualization. Sahar A. Nasser: Methodology, Validation, Investigation, Writing-review and editing, Funding acquisition. Both authors contributed to data interpretation and approved the final manuscript.
     
    Ethics statement
     
    This study involved laboratory analysis of camel milk samples and did not require ethical approval from an institutional review board or animal ethics committee, as no live animals or human subjects were directly involved in experimental procedures beyond standard milk collection under hygienic conditions. All analyses followed international standards for food safety and quality assessment.
     
    Funding
     
    This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
     

    CONFLICT OF INTEREST

    The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

    REFERENCES


    1. Abduku, H. and Eshetu, M. (2024). Physico-chemical properties and processing characteristics of camel milk as compared with other dairy species: A review. Asian Journal of Dairy and Food Research. 43(1): 1-7. doi: 10.18805/ajdfr.DRF-303.

    2. Abou-Soliman, N.H.I., Abd-Rabou, H.S., Awad, S. and Ibrahim, A.A. (2025). Impact of thermal treatment on the quality, total antioxidant and antibacterial properties of fermented camel milk. Scientific Reports. 15(1): 8533. https:// doi.org/10.1038/s41598-025-91548-1.

    3. Alhassani, W. E. (2024). Camel milk: Nutritional composition, therapeutic properties and benefits for human health. Open Veterinary Journal. 14(12): 3164-3180. https://doi.org/10.5455/ OVJ.2024.v14.i12.2.

    4. Aljasass, F.M., Hamad, S.H., Aleid, S.M. and El Neshwey, A.A. (2023). Evaluation of high hydrostatic pressure as an alternative method for camel milk preservation. Current Research in Nutrition and Food Science Journal. 11(3): 1153-1165. https://doi.org/10.12944/crnfsj.11.3.20.

    5. Al-Thaibani, A., Mostafa, H., Al Alawi, M., Sboui, A., Hamed, F., Mudgil, P. and Maqsood, S. (2024). Camel milk whey powder formulated using thermal (spray-drying process) and non-thermal (ultrasonication) processing methods: Effect on physicochemical, technological and functional properties. Ultrasonics Sonochemistry. 111: 107097. https://doi.org/10.1016/j.ultsonch.2024.107097.

    6. Al-Zoreky, N.S., Almathen, F.S., Al hashedi, S.A. and AL-Farga, A. (2024). Evaluation of heat stability of camel milk (sterilized and nonevaporated). Journal of Food Quality. 2024(1). https://doi.org/10.1155/2024/5564251.

    7. AOAC. 2019. Official Methods of Analysis of AOAC International. 21st ed. AOAC International, Rockville, MD, USA.

    8. Arain, M.A., Salman, H.M., Ali, M., Khaskheli, G.B., Barham, G.S., Marghazani, I.B. and Ahmed, S. (2024). A review on camel milk composition, techno-functional properties and processing constraints. Food Science of Animal Resources.  44(4): 739-757. https://doi.org/10.5851/kosfa.2023.e18.

    9. Atwaa, E.S.H., Shahein, M.R., Raya-Álvarez, E., Abd El-Sattar, E.S., Hassan, M.A.A., Hashim, M.A., Dahran, N., El- Khadragy, M.F., Agil, A. and Elmahallawy, E.K. (2023). Assessment of the physicochemical and sensory characteristics of fermented camel milk fortified with Cordia myxa and its biological effects against oxidative stress and hyperlipidemia in rats. Frontiers in Nutrition. 10: 1130224. https://doi.org/10.3389/fnut.2023.1130224.

    10. Chetia, J., Panda, T.C., Kumari, S. and Seth, D. (2023). Effect of non-thermal processing on nutritional and functional properties of milk and milk products-A review. Indian Journal of Animal Health. 62(2-Spl). https://doi.org/ 10.36062/ijah.2023.spl.03323

    11. Danielyan, L., Barseghyan, A., Melkumyan, I., Mnatsakanyan, N., Khachanyan, M., Harutyunyan, M. and Hovhannisyan, H. (2025). Transforming ordinary yogurt into functional yogurt using low doses of ethanolic extract of Origanum vulgare L. Functional Food Science. 5(8): 378-392. Online ISSN: 2767- 3146. https://doi.org/10.31989/ffs.v5i8. 1725.

    12. De Vela, R.J.L. and Elepano, A.R. (2024). Drying and color kinetics of decorticated queen pineapple (Ananas comosus Linn.) fiber bleached with hydrogen peroxide solution. Research in Agricultural Engineering. 70(2): 73-81. https://doi.org/10.17221/47/2023-rae.

    13. Drici, H., Khelef, D., Kherouatou, N., Ayachi, A., Benmahdi, L., Hamadache, A., Bouyoucef, A. and Aggad, H. (2025). Heat-stable camel milk-base culture medium efficiency to improve microbiological analysis of raw camel milk.  Asian Journal of Dairy and Food Research. 44(2): 186- 192. doi: 10.18805/ajdfr.DRF-528.

    14. Fguiri, I., Sboui, A., Atigui, M., Arroum, S., Ayeb, N., Dbara, M., Hammadi, M. and Khorchani, T. (2022). Camel milk curd properties: Application of a kiwi juice as a coagulant. Asian Journal of Dairy and Food Research. 42(1): 14- 19. doi: 10.18805/ajdfr.DRF-275.

    15. Field, A. (2024). Discovering Statistics using IBM SPSS Statistics (6th ed.). SAGE Publications.

    16. Gebrehiwot, H.H. and Banat, F. (2025). Powdered camel milk production and changes occurring along the processing steps and storage conditions: A comprehensive review.  Food Chemistry. 493(Pt 4): 146050. https://doi.org/ 10.1016/j.foodchem.2025.146050.

    17. Harizi, N., Zouari, A., Rokbeni, N., Ben Zid, M., M’hiri, N., Salem, A., Ayadi, M.A. and Boudhrioua, N. (2023). Amino acids and protein profiles of defatted camel and cow milk fractions: Correlation with their in vitro antioxidant and antidiabetic activities. Frontiers in Nutrition. 10: 1295878.  https://doi.org/10.3389/fnut.2023.1295878.

    18. Hernandez, A.M., Berto, M.I. and Bianchini, E.M.G. (2025). Viscosity study of maternal and formula milks according to the assessment proposed by the international dysphagia diet standardisation initiative model: A comparison with rheological assessment. CoDAS. 37(3): e20240049. https://doi.org/10.1590/2317-1782/e20240049en.

    19. Hou, W., Ma, X., Yu, Z., Bari, L., Jiang, H., Du, Q., Fan, R., Wang, J., Yang, Y. and Han, R. (2024). Impact of ultrasonic and heat treatments on the physicochemical properties and rennet-induced coagulation characteristics of milk from various species. Ultrasonics Sonochemistry. 111: 107084. https://doi.org/10.1016/j.ultsonch.2024.107084.

    20. Kapoor, R., Karabulut, G., Mundada, V. and Feng, H. (2024). Unraveling the potential of non-thermal ultrasonic contact drying for enhanced functional and structural attributes of pea protein isolates: A comparative study with spray and freeze-drying methods. Food Chemistry. 439: 138137. https://doi.org/10.1016/j.foodchem.2023.138137.

    21. Krstovic, S., Jakšic, S., Miljaniæ, J., Ilièic, B., Živkov, B.M., Guljaš, D., Damjanovic, M. and Jajic, I. (2025). Annual and seasonal variations in aflatoxin M1 in milk: Updated health risk assessment in Serbia. Toxins. 17(11). https://doi.org/ 10.3390/toxins17110544.

    22. Li, X., Qi, B., Zhang, S. and Li, Y. (2023). Effects of homogeneous and ultrasonic treatment on casein/phosphatidylcholine complex-emulsions: Stability and bioactivity insights. Ultrasonics Sonochemistry. 97: 106457. https:/ /doi.org/10.1016/j.ultsonch.2023.106457.

    23. Mazumder, J.A., Ali, A.H. and Banat, F. (2024). Emerging non- thermal treatment approaches for camel milk: A review.  NFS Journal. 37: 100198. https://doi.org/ 10.1016/j.nfs.2024.100198.

    24. Mbye, M., Akram, A., Mohamed, H. and Banat, F. (2025). Impact of ultrasonication and thermal pre-treatments on the quality, proteolysis and bioactive properties of camel milk cheese. Lebensmittel-Wissenschaft Und Technologie [Food Science and Technology]. 232: 118414. https:/ /doi.org/10.1016/j.lwt.2025.118414.

    25. Mbye, M., Ayyash, M., Abu-Jdayil, B. and Kamal-Eldin, A. (2022). The texture of camel milk cheese: Effects of milk composition, coagulants and processing conditions.  Frontiers in Nutrition. 9: 868320. https://doi.org/10.3389/ fnut.2022.868320.

    26. Mbye, M., Mohamed, H., Ramachandran, T., Hamed, F., AlHammadi, A., Kamleh, R. and Kamal-Eldin, A. (2021). Effects of pasteurization and high-pressure processing of camel and bovine cheese quality and proteolysis contribution to camel cheese softness. Frontiers in Nutrition. 8: 642846. https://doi.org/10.3389/fnut.2021.642846.

    27. Moatsou, G. (2024). Emerging technologies for improving properties, shelf life and analysis of dairy products. Foods (Basel, Switzerland). 13(7): 1078. https://doi.org/10.3390/foods 13071078.

    28. Mohammed, A.A. and Alshaibani, N. (2024). Camel milk yield and composition and its adjuvant potential impacts on health of consumers: A review. Indian Journal of Animal Research. 59(2): 177-184. doi: 10.18805/IJAR.BF-1872.

    29. Mudgil, P., Alkaabi, A. and Maqsood, S. (2022). Ultrasonication as a novel processing alternative to pasteurization for camel milk: Effects on microbial load, protein profile and bioactive properties. Journal of Dairy Science. 105(8): 6548-6562. https://doi.org/10.3168/jds.2021-20979.

    30. Niu, Q., Liu, E., Huo, C., Zhang, F., He, R., Yang, J. and Zhao, Z. (2025). Effects of transglutaminase and heat treatment on the structure and gelation properties of camel casein protein. Foods (Basel, Switzerland). 14(9): 1644. https:/ /doi.org/10.3390/foods14091644.

    31. Osaili, T.M., Dhanasekaran, D.K., Hasan, F., Obaid, R.S., Al-Nabulsi, A.A., Olaimat, A.N., Ismail, L.C. et al.  (2025). Changes in microbial safety and quality of high-pressure processed camel milk. Foods (Basel, Switzerland). 14(2): 320. https://doi.org/10.3390/foods14020320.

    32. Pandiselvam, R., Mitharwal, S., Rani, P., Shanker, M. A., Kumar, A., Aslam, R., Barut, Y.T., Kothakota, A., Rustagi, S., Bhati, D., Siddiqui, S. A., Siddiqui, M. W., Ramniwas, S., Aliyeva, A. and Mousavi, K.A. (2023). The influence of non- thermal technologies on color pigments of food materials: An updated review. Current Research in Food Science. 6: 100529. https://doi.org/10.1016/j.crfs.2023. 100529.

    33. Pegu, K. and Arya, S.S. (2023). Non-thermal processing of milk: Principles, mechanisms and effect on milk components. Journal of Agriculture and Food Research. 14: 100730. https://doi.org/10.1016/j.jafr.2023.100730.

    34. Rabbani, A., Ayyash, M., D’Costa, C. D. C., Chen, G., Xu, Y. and Kamal-Eldin, A. (2025). Effect of heat pasteurization and sterilization on milk safety, composition, sensory properties and nutritional quality. Foods (Basel, Switzerland). 14(8): 1342. https://doi.org/10.3390/foods14081342.

    35. Safwa, S.M., Ahmed, T., Talukder, S., Sarkar, A. and Rana, M.R. (2024). Applications of non-thermal technologies in food processing Industries-A review. Journal of Agriculture and Food Research. 18: 100917. https:// doi.org/10.1016/j.jafr.2023.100917.

    36. Siddiqui, S.A., Khan, S., Bahmid, N.A., Nagdalian, A.A., Jafari, S.M. and Castro-Muñoz, R. (2024). Impact of high-pressure processing on the bioactive compounds of milk-A comprehensive review. Journal of Food Science and Technology. 61(9): 1632–1651. https://doi.org/10.1007/ s13197-024-05938-w.

    37. Sun, M., Shao, W., Liu, Z., Ma, X., Chen, H., Zheng, N. and Zhao, Y. (2024). Microbial diversity in camel milk from Xinjiang, China as revealed by metataxonomic analysis. Frontiers in Microbiology. 15: 1367116. https://doi.org/10.3389/ fmicb.2024.1367116.

    38. Thi, H.B.A., Cozzolino, D., Zisu, B. and Chandrapala, J. (2020). Effects of high and low frequency ultrasound on the production of volatile compounds in milk and milk products- A review. The Journal of Dairy Research. 87(4): 501- 512. https://doi.org/10.1017/S0022029920001107.

    39. Tobolková, B. and Durec, J. (2023). Colour descriptors for plant- based milk alternatives discrimination. Journal of Food Science and Technology. 60(9): 2497-2501. https:// doi.org/10.1007/s13197-023-05773-5.

    40. Wang, Y.H., Wuren, T., Zhai, B.T., Er, D. and Yang, H. (2024). Impact of storage conditions on the quality of raw camel milk. Food Science of Animal Resources. 44(6): 1345- 1357. https://doi.org/10.5851/kosfa.2024.e52.

    41. Zhao, X., Guo, Y., Zhang, Y., Pang, X., Wang, Y., Lv, J. and Zhang, S. (2023). Effects of different heat treatments on Maillard reaction products and volatile substances of camel milk. Frontiers in Nutrition. 10: 1072261. https://doi.org/ 10.3389/fnut.2023.1072261.
    In this Article
      Contact us
      Follow us
      Published In
      Asian Journal of Dairy and Food Research

      Editorial Board

      View all (0)