Antioxidant Potential of Fruit-based Phytochemical on the Quality Attributes and the Shelf-life of Chevon Nuggets

Chevon or goat meat is a significant protein source throughout the world especially in the developing countries. The black Bengal goat (Capra hircus bengalensis), distributed in the  eastern part of India, has long been appreciated for its superior meat quality and carries a huge domestic demand with no social, cultural and religious restrictions (Biswas, 2010). Due to changing life style, work culture and increasing number of women entering workforce the “heat and serve” type ready to eat meat products are in great demand (Verma et al., 2013). This increased demand also increases the concerns for meat safety and quality.  Lipid oxidation in meat and meat products is one of the major causes of their quality deterioration, the other being microbial spoilage. Production of value-added meat products require a number of activities like physical alteration, heat treatment etc. Such activities lead to development of oxygenated free radicals which in-turn initiates the oxidation of polyunsaturated fatty acids causing destruction of the natural antioxidant systems. Moreover, extensive handling and improper sanitary conditions both during production and storage would likely increase the microbial load of the end product. The above-mentioned factors lead to deterioration of the storage stability of the final product. Concerns over the use of synthetic preservatives and consumers’ assurance over natural counterparts have prompted the food industry to extensively explore the potential of nature surrounding us. Fruits and fruit by products are known to be rich sources of antioxidant and antimicrobial compounds and their frequent consumption is associated with a lower risk of various diseases as well as cancer (Temple, 2000). Reports regarding use of guava, bael fruit and dragon fruit in the meat products either as antioxidant, antimicrobial or as a source of dietary fiber are very limited.
               
Therefore, our study was to determine the antioxidant and antimicrobial properties of fruit powder incorporation in improving quality and oxidative Chevon nuggets by incorporating easily available, economically viable dietary sources during refrigerated storage (4±1°C) and their effects on various physico-chemical, textural and sensory attributes of products.

Goat meat (Chevon)
 
The experiment was conducted at the Department of Livestock Products Technology, West Bengal University of Animal and Fishery Sciences, Kolkata, during 2018-2019. Black Bengal goats aged 9-10 months and weighing 12-15 kg were procured from a local Farm at Belgachia, Kolkata. The goats were slaughtered as per the traditional halal method at the experimental slaughter house of Department of Livestock Products Technology. The dressed carcasses were brought to the laboratory immediately and chilled at 4±1°C for 12-18 hr and then deboned manually. The skin, external fascia, fat and all separable connective tissues were removed and the experimental samples for each trial were taken from the pooled deboned meat of a carcass. The boneless meat and fat were packed separately in low density polyethylene (LDPE) bags and stored in a deep freezer at -18±1°C until further use.
 
Raw materials and chemicals
 
Fresh guava, bael and dragon fruits were purchased from local market of Belgachia, Kolkata, brought to the laboratory and washed properly with clean portable water. For this study, whole sliced guava fruit, bael pulp and the peel of dragon fruits were dried separately in a hot air oven (50±1°C) for 7-8 hrs. The dried guava, bael pulp and dragon fruit peel were ground to a fine powder and sieved through a fine mesh with an average particle size of <1.0 mm. These samples were then individually and aerobically packed in UV sterilized low density polyethylene (LDPE) containers and stored at 4±1°C until further utilization.
       
All the spice ingredients were cleaned, dried in hot air oven at 60°C for 2 hr, cooled in a dessicator and then ground using proportionate quantity to obtain the dry spices mix used for the preparation of nuggets. Similarly, a condiment mixture is prepared having onion, ginger and garlic in the ratios 3:1:1 and this mixture is also added to the meat during emulsion formation. All the chemicals used were of analytical grade and were procured from standard firms (Himedia). Rest all products used viz. common salt, oil, refined wheat flour etc. were from commercial food grade suppliers.
 
Estimation of dietary fiber, total phenolics, carotenoid and Vitamin C content of fruit powder
 
The dietary fiber content of fruit powder were determined by the methods of AOAC (1995).
 
Total phenolics content
 
The concentration of total phenolics in guava powder (GP), bael pulp powder (BPP) and dragon fruit peel powder (DFPP) was determined by the Folin-Ciocalteu (F-C) assay (Escarpa and Gonzalez, 2001) with slight modifications.
 
Total carotenoid content
 
The method used for determining total carotenoids was performed on a UV-Vis spectrophotometer (Prache et al., 2003).
 
Vitamin C content
 
Sample preparation, chromatography conditions, identification and quantification of vitamin C in fruit powder by HPLC method was performed using the method described by Czech Agriculture and Food Inspection Authority (2005).  
        
Preparations of chevon nuggets
 
One kg formulation of emulsion was made for each treatment. Control formulation consisted of 70% minced meat, 10% refined mustard oil, 10% ice flakes, 1.6% salt, 0.3% tripolyphosphate, 0.3% sugar, 1.8% dry spices powder, 3% condiments and 0.3% refined wheat flour. Sodium nitrite at 150 ppm was also added to the above formulations. In treated formulations, guava powder (1.5%), bael pulp powder (1.5%), dragon fruit peel powder (1.5%) powder were incorporated by replacing an equal amount minced meat in the control formulation. The emulsions were made in a bowl chopper (Talsa Ltd, Germany). Meat emulsion (approx.750 g) was placed into stainless steel moulds (18x12x4 cm), tightly packed and cooked in a steam at atmospheric pressure for 35 min. The temperature of the steam oven during cooking was above 100°C. The meat blocks were cooled to room temperature and then cut into nuggets of suitable sizes. About 200 g nuggets were packed in separate polyethylene pouches and stored at 4±1°C. They were evaluated for physico-chemical parametres (viz. pH, proximate composition), textural profile and sensory evaluation on day 0. To determine the storage stability the thiobarbituric acid values and microbial quality were analysed at 5 days interval up to 20 days. Each component was measured in triplicate and the entire experiment was replicated thrice.
 
Analytical methods
 
The moisture, protein, fat and ash content of fruit powder and Chevon nuggets were determined by the methods of AOAC (1995). Emulsion stability of goat meat nuggets was determined as per procedure of Baliga and Madaiah (1971).  The pH of the nuggets was determined by the method suggested by Troutt et al., (1992). Thiobarbituric acid number (mg malonaldehyde/kg) of the samples was determined using the extraction method described by Witte et al., (1970). Total plate count (TPC) and psychrophilic count were determined by APHA (1992) using pour plate method. The sensory parameters of the Chevon nuggets were evaluated by mean descriptive analysis method using 8 points hedonic scale (Keeton et al., 1984).
 
Statistical analysis
 
All the data obtained during the present investigation were analyzed statistically to draw valid conclusion by using SPSS (Version 24.0) software. The data obtained were analyzed by randomized block design (4 treatmentsx6 no of samples) and subsequent one-way ANOVA analysis except storage study parameters were analyzed by complete randomized design for (3 treatmentx6 no of samples x5 storage days) by two-way ANOVA. Further the significance between the data was compared by Tukey’s Post Hoc Test by SPSS-24® software package. A probability value of p<0.05 was described as significant and p<0.01 was noted as highly significant.

Dietary fibre, total phenolics, total carotenoids and Vitamin C content of fruit fiber powder
 
The Dietary fibre, total phenolics, total carotenoids and Vitamin C content of GP, BPP and DFPP are presented in Table 1. The dietary fibre content of DFPP recorded the significantly(p<0.05) higher value followed by GP and BPP. Bael pulp powder possessed significantly (P<0.05) higher phenolics content followed by DFPP and GP. Significantly (P<0.05) higher total carotenoids and Vitamin C were found in GP in comparison to BPP and DFPP. The DF content of GP in the present study is similar with the findings of Jimenez-Escrig et al. (2001) who reported total dietary fibre content in dried guava as 48.55 to 49.42%. Suvimol and Anprung (2008) reported total DF of bael fruit pulp as 10.84g/100g DW. Plant phenolic compounds are one of the most desirable bioactive compounds with strong antioxidative capacity (Roohinejad et al., 2017). Because of their ability to scavenge free radical, chelate pro-oxidant metals, potential role as reducing agents and quenchers of singlet oxygen (Mohajer et al., 2016). According to Corrêa et al., (2011), total phenolics, expressed as equivalent of gallic acid (GAE), varied from 158 to 447 mg GAE/100 g in guava. Suvimol and Pranee (2008) observed that bael fruit pulps had total phenolic content of 87.34 mg GAE/g DW, whereas Jain et al., (2011) reported the total polyphenols (mg GAE/g) in bael fruit extract as 95.33, which corresponds to the values obtained in the present study. The total phenolic contents of dragon fruit peel were reported as 36 mg GAE/100g (Manihuruk et al., 2017). In this study, significantly higher carotenoids were observed in guava powder, which correlated with the values (0.78 to 2.93 mg/100 g) as reported by Thaipong et al., (2006) in pink pulp guava. As compared to Charoensiddhi and Anprung (2008) who reported that bael fruit pulps had total carotenoid content of 32.98 µg/g DW we analyzed that the carotenoid content of BPP was 0.15 mg/kg. For DFP the total carotenoids (mg of β-carotene/100 g of edible portion) was found to be 0.86±0.01 by Can-Cauich et al. 2017 which is in confirmation with the values we observed in our study. The variation in carotenoid content might be due to the variety of the fruit and drying method used for powder preparation.    
 

 
Proximate composition
 
The pH and proximate composition of Chevon nuggets treated with 1.5% of GP, BP and DFPP are presented in Table 2. Addition of fruit powder significantly (P<0.05) affected the pH of nuggets. The pH values of Chevon nuggets with fruit powder were lower than the control batch. The low pH values of treated nuggets could be attributed to the added fruit powder, which were a good source of ascorbic acid. This observation was in confirmation with Manihuruk et al., (2017) who demonstrated that addition of guava powder in sheep nuggets and dragon fruit peel extract in beef sausages, respectively, lowered the pH of the final product.
 

       
Incorporation of fruit powder significantly (P<0.05) affected the moisture, fat and ash percentage of nuggets, however, protein percentage did not show any significant (P>0.05) effect. The highest moisture, fat and ash percentage were recorded with nuggets treated with DFPP. The trend observed in case of moisture and ash percentage was DFPP>GP>BPP>Control whereas in case of fat percentage it was DFPP>GP³Control>BPP. The higher moisture percentage in fruit powder treated nuggets could be due to absorption of added water by the powder incorporated during product preparation. Similar results were recorded in sheep meat emulsion with guava powder (Verma et al., 2013) and Chevon nuggets prepared with BPR (Das et al., 2014). However, Manihuruk et al., (2017) observed that addition of dragon fruit peel extract did not affect the moisture, fat or ash content of beef sausage.
       
The results regarding protein percentage in the present study corresponded to the observations of Verma et al., (2013), who also reported that there was no significant difference in protein percentage of sheep meat nuggets treated with 0.5% and 1% guava powder. Proximate composition of emulsion and nuggets were not affected significantly (p>0.05) due to addition of BPR (Das et al., 2014). According to Manihuruk et al., (2017), protein content of beef sausages was unaltered due to incorporation of red dragon fruit peel extract. The high fat percentage of dragon fruit peel might have increased the fat content of nuggets treated with DFPP in the present study. Ash percentage in the present study correlated with the results of Das et al., (2014).
 
Texture profile analysis
 
Addition of GP, BPP and DFPP to Chevon nuggets resulted in significant (P<0.05) changes in hardness, springiness, cohesiveness, gumminess and chewiness values (Table 3). Hardness, cohesiveness, gumminess and chewiness values were significantly (P<0.05) decreased after addition of fruit powder except springiness, which increased significantly (P<0.05) in treatment groups. The lowest values for hardness, cohesiveness, gumminess and chewiness were recorded in nuggets treated with DFPP. In the present study, incorporation of fruit powder in Chevon nuggets made them softer. These findings were in coherence with the observations of Vidyarthi et al., (2022) in fish nuggets treated with different fruit powder. Rajkumar et al., (2016) reported significantly lower springiness and loss of elasticity in nuggets incorporated with aloe-vera gel and lower gumminess in mutton nuggets treated with apple pomace (Huda et al., 2014). However, Verma et al., (2013) did not find any significant changes in sheep meat nuggets after addition of guava powder. The contradictory results in textural parameters might be due to the difference in the type and amount of fiber added in the products.
 

 
Sensory properties
 
The treatment of Chevon nuggets with GP, BPP and DFPP had significant (P<0.05) effect on sensory attributes viz. appearance, flavor, texture, tenderness and juiciness and results (Table 4). The nuggets treated with GP had significantly (P<0.05) higher scores for appearance and flavour as compared to control and other treatment groups, whereas BPP treated nuggets had the highest texture, tenderness and juiciness scores. Overall, the acceptability of control nuggets was significantly (P<0.05) higher than other treatment groups; however, the sensory attributes of treated nuggets were acceptable as evaluated by the sensory panelists. Elhadi et al., (2017) reported that color, flavor, tenderness and juiciness scores of moringa leaf powder incorporated chicken patties were significantly (P<0.05) lower than the control samples. No significant (P<0.05) effect on sensory properties was found in sheep meat nuggets treated with guava powder (Verma et al., 2013) or M. oleifera leaves extract enriched cooked Chevon patties (Das et al., 2012). Das et al., (2014) observed that the overall acceptability of the Chevon nuggets increased with the added BPR, however, the difference was statistically nonsignificant. In the present study, appearance, flavour, texture, tenderness and juiciness scores were higher in treatment groups, although overall acceptability scores were reported to be higher in control group.
 

 
Thiobarbituric acid (TBA) values
 
The thiobarbituric acid (TBA) value (mg malonaldehyde/kg) of the Chevon nuggets treated with GP, BPP and DFPP were recorded on day 0 and then at 5 days interval upto 20^th day (Table 5). The treatment and storage time had a statistically significant (P<0.05) effect on TBA values of Chevon nuggets. Incorporation of fruit powder significantly (P<0.05) reduced the lipid oxidation rate of Chevon nuggets during refrigerated storage. Nuggets treated with DFPP had the lowest TBA value during entire storage period followed by BPP, then GP and finally control. Although, the TBA values were increased significantly throughout the storage period, irrespective of any treatment, the values were below the threshold limit of 1-2 mg/kg for rancidity (Watts, 1962). The significant (P<0.05) increase in TBA value with storage period in all groups might be attributed to increased lipid oxidation and production of volatile metabolites in the presence of oxygen during aerobic storage, however, the values were within the acceptable limit till the 20^th day. These findings indicated that the phenolic compounds in the fruit powder mitigated the lipid peroxidation and development of oxidative rancidity in the nuggets. The carotenoids and Vitamin C content might have also contributed to its strong antioxidant ability. Verma et al., (2013) reported that the increase in TBARS number in guava powder treated samples was very slow and remained lowest (0.68 mg malonaldehyde/kg sample) up to the 15^th day.
       

 
Microbiological parameters
 
The total plate count (TPC), psychrophilic count and coliform count (log10 cfu/gm) of the Chevon nuggets treated with 1.5% GP, BPP and DFPP and control were recorded at 5 days interval up to 20^th day (Table 6). Incorporation of fruit powder significantly (P<0.05) improved the microbial stability of treatment groups and the best results were observed in nuggets treated with DFPP. On day 0, no psychrophilic growth was observed in any of the treated nuggets, however, the count increased significantly (P<0.05) in all the groups throughout the storage period. There was no growth of coliforms in fruit powder treated nuggets up to 15^th day of storage period. The antimicrobial activity of fruit powder in Chevon nuggets in the present study might be due to the presence of many bioactive components, including vitamins, minerals and carotenoids.  According to Barba et al., (2017) plant extracts are known for their high antimicrobial activity against both foodborne pathogenic and spoilage microorganisms. Similar results were obtained by Das et al., (2014) in Chevon nuggets incorporated with BPR.
 
 

Guava, bael pulp and dragon fruit peel powder are rich sources of phenolic compounds, total carotenoids and vitamin C. Incorporation of fruit powder can be used as a functional ingredient to modify the physicochemical properties of emulsion meat products and improve textural parameters without affecting their acceptability. Fruit powder’s strong antioxidant and antimicrobial properties can be used in the meat industry to maintain the microbial stability and minimise oxidation of meat and meat products throughout storage upto 20 days.

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