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Full Research Article

Role of Salt and Turmeric in Modulating Cooking and Organoleptic Traits of Whole Gutted Rohu (Labeo rohita) under Refrigerated Storage (4±1°C)

A
Ankures Bhattacharya1,*
0000-0001-5974-5902
S
Supratim Chowdhury2
0000-0002-7166-3093
1Department of Fish Processing Technology, School of Fisheries, Centurion University of Technology and Management, Paralakhemundi, Gajapati-761 211, Odisha, India.
2Department of Fish Processing Technology, Faculty of Fishery Sciences, West Bengal University of Animal and Fishery Sciences, Chakgaria, Panchasayar, Kolkata-700 094, West Bengal, India.

ABSTRACT

Background: Fish is highly perishable due to rapid microbial and enzymatic spoilage, causing major post-harvest losses, particularly in Rohu (Labeo rohita). Rising concerns over synthetic preservatives have shifted focus toward natural agents like salt and turmeric in organoleptic and cooking qualities.

Methods: The study aims to assess the cooking qualities likely cooking yield, cooking loss, shrinkage of whole gutted rohu samples during 13 days of refrigerated storage and the organoleptic score by using hedonic score method.

Result: The results signified that the samples treated with salt and turmeric in combination showed better cooking parameters throughout the 13 days of refrigerated storage and significantly varies with the control and salt treated whole gutted rohu samples. The salt and turmeric treated samples showed the highest cooking yield (53.17%), lowest cooking loss (46.83%) and lowest shrinkage (6.74%) on 13th day of storage. The sensory attributes demonstrated that combined treatment with salt and turmeric significantly preserved the sensory quality and minimized deterioration over the storage period. Turmeric’s antimicrobial and antioxidant properties, along with salt’s dehydration effect, contributed synergistically to maintaining product integrity.

INTRODUCTION

The perishable nature of fish underscores its critical role in the livelihoods and nutritional well-being of populations in developing countries. In India, fish is also considered one of the main food for human diet (Biswas, 2024). According to the Food and Agriculture Organization, fish is a staple source of protein for a significant proportion of the global population, with more than 3.3 billion people deriving at least 20% of their annual protein intake from fish and another 1.3 billion people obtaining 15% of their animal protein from this valuable resource (FAO, 2020). The global demand for fish as a source of protein is substantial, with fish accounting for a considerable share of animal protein intake (17%) and overall protein consumption (7%) in 2017. Notably, global fish production has reached unprecedented levels, with an estimated 179 million tonnes produced in 2018. Of this, a significant proportion (156 million tonnes) was directed towards human consumption, resulting in an estimated annual per capita availability of 20.5 kg and highlighting the critical role of fish in meeting global nutritional needs (FAO, 2020). Labeo rohita, known colloquially as Rohu, is a freshwater fish species of paramount importance in Indian aquaculture. With a long history of domestication and a prominent role in traditional carp polyculture systems, Rohu has emerged as a highly sought-after species, driven by its desirable characteristics and strong market demand. Generally, it is found in India, Bangladesh, Myanmar and Pakistan (Talwar and Jhingran, 1991). In India Rohu has been transplanted into all the rivers of Northern, Central and Eastern part and also introduced in some river of the peninsular India and Srilanka. Rohu is an omnivorous fish coming under family Cyprinidae and order Cypriniformes is extensively used in aquaculture. It is highly preferred for culture and contributes more than 80% of the major carp culture in India. Traditionally, the Indian cuisine uses turmeric and salt for preservation of fish. Among the traditional practices, curing is one of the old, convenient method for preserving fish by reducing the spoilage (Jakhar et al., 2018). Both these ingredients are antimicrobial in nature and taste enhancers. Turmeric additionally has antioxidant properties. Salt is one of the oldest natural preservatives used to prevent the spoilage taking place in storing the fish. Salt has its antimicrobial, antibacterial, biochemical activity, which makes it widely usable preservatives. Salt, generally the common salt (NaCl) is used that penetrates the tissue. Salt inhibits the growth of microorganisms by removing water out of the microbial cells by osmosis. Salt lowers the moisture content of the fish to a level where any bacterial process and enzymatic activity cannot occur, as a result the cell collapse itself. This is the antimicrobial activity of salt. In addition of salt’s suppressing effect on food spoilage bacteria, salt has antibacterial activities against various food borne pathogens like Clostridium botulinum. (Sallam, 2007). High concentration of salt also can cause myofibrils contraction and protein dehydration. Use of salt as preservative can improve the sensory attributes of final fish and also improve texture and prolong shelf life of fish.
       
Turmeric, a herb of Zingiberaceae family is a good source of natural antioxidant and antimicrobial agent (Negi et al., 1999; Kumar et al., 2006). Also, Turmeric is used in as natural preservative to suppress the growth of several pathogenic bacteria. Turmeric antibacterial activity can inhibit Clostridium botulinum and other gram-positive bacteria like Bacillus subtilis. Turmeric helps to improve the meat quality of fish and also decrease the microbial load in fish. It is one of the most widely used as an antiseptic, anticancer agent. It also reduces the biogenic amine formation in fish during the chilled storage and reduces the foul odor during prolonged storage in refrigerated condition and increase the shelf life of fish. Turmeric also controls other biochemical parameters and help to preserve the fish in good condition. Curcumin, the active component of Turmeric is a potent antioxidant (El-Bahr et al., 2007) and has hepatoprotective properties. Turmeric contains turmerin, a water-soluble peptide that exhibits potent antioxidant activity, effectively scavenging free radicals and terminating oxidative chain reactions. Turmeric also has antiperoxidant activity on several natural fish lipids and also reduces the level of lipid peroxides. It is a potent inhibitor of lipid peroxidation.  Turmeric is also used in food processing industry as additives for pigmentation and flavor enhancement (Sirisidthi et al., 2016). Turmeric also improves sensory quality of fish and making it acceptable towards the panelists. Turmeric is known as natural dye, the pigment component of turmeric, Curcumin helps to maintain and improve the color of fish. Turmeric also improves the texture, flavor and aroma of fish. Due to this reason, turmeric is widely used in house hold before cooking and also during storage of fish.
       
In the present study the influence of turmeric and salt addition on the quality parameters of whole, gutted rohu was evaluated under refrigerated condition. Refrigeration, salt and turmeric are expected to offer a series of hurdles to microbial growth and hence retard the spoilage process. Apart from hurdle technology turmeric is expected to act as an antioxidant and both the additives may improve the shelf life of the whole gutted rohu under refrigerated storage.

MATERIALS AND METHODS

Raw material
 
Fresh Rohu, locally known as Rui or Rohu (Labeo rohita) was brought from Parijoy Fish Farm, Naihati, North 24 Parganas during the month of July, 2020 selected through simple random sampling for inclusion in this study. These freshly harvested fishes were carefully transferred in insulated box under iced condition transported to the Fish Processing Technology Laboratory, Faculty of Fisheries Sciences, within 1-2 hours of collection.
 
Fish processing
 
Immediately after transferring the samples into laboratory, they were washed thoroughly in running water to remove the dirt, slime and other physical substances. After washing the samples were beheaded, eviscerated and descaled manually following which fishes were prepared weighting about 70-100 g under strict adherence to hygienic and sanitary protocols to minimize the risk of cross-contamination.
 
Incorporation of preservatives and storage study
 
Processed fishes are divided into three parts like, C, T1 and T2. First part was taken as Control (C) without any treatment. Sample T1 and T2 were mixed with salt (1% NaCl) and salt and Turmeric (1% salt +1% turmeric) respectively. After that, samples were stored under refrigerated condition maintained at a temperature of 4±1°C.
 
Estimation of cooking properties
 
Cooking loss
 
The extent of cooking loss was quantified according to the method described by Niamnuy et al., (2008), wherein the mass difference between raw and cooked fish steaks was measured and calculated. Each sample was cooked on a frying pan with hot oil and the oil temperature was at 150°C for 7 mins. Post-cooking, samples were cooled to room temperature and reweighed to determine cooking loss, calculated as follows:

 
Cooking yield
 
The cooking yield of fish was assessed according to the methodology outlined by Aleson-Carbonell et al. (2005). Samples were cooked in a frying pan with hot oil at 150°C for 7 minutes. Following cooking, samples were cooled to room temperature and subsequently reweighed to determine yield.

 
Shrinkage
 
Shrinkage (%) was calculated as by simple mathematical formula and this was calculated from the difference in the length, width and height of fish fillet before and after cooking method. Each sample was cooked on a frying pan with refined sunflower oil and the oil temperature was at 160°C for 4 mins. After cooking the samples were cooled down to room temperature and then took the length, width and height of fish fillet. The shrinkage was calculated as follows:

 
Here,
L = Length before cooking.
L1 = Length after cooking.
 
Sensory evaluation
 
Sensory evaluation of cooked fish was conducted by a panel of at least 6 experienced assessors at regular intervals during storage. The panellists assessed the samples based on a comprehensive set of attributes, including colour, shape, odour, taste and texture, utilizing a 9-point hedonic scale (Bognar, 1998). The scale’s numerical ratings (9-1) corresponded to specific descriptive categories for each attribute (Table 1).

Table 1: Descriptions of 9-point hedonic scale.



The sensory quality was calculated by following equation:

 
Where,
Fi = Colour (browning).        
F2 = Shape.
G = Odour + taste.
T = Texture.
 
Statistical analysis
 
Prior to analysis, data were verified for normal distribution using normality plots. One-way analysis of variance (ANOVA) was then performed to identify significant differences among means at a significance level of α = 0.05. Statistical analyses were conducted using Microsoft Office Excel 2007 and R software (Version 2.14.1). Post-hoc comparisons were made using Tukey’s honest Significant Difference (HSD) test to determine significant differences between treatment groups.

RESULTS AND DISCUSSION

Cook yield (CY) of whole gutted rohu under refrigerated storage (4±1°C)
 
The changes in cook yield of whole gutted Rohu samples under refrigerated storage (4±1°C) are given in Table 2. A decreasing trend was found in cooking yield percentage for all samples during the 13 days of investigation. The cooking yield values for the control (C) whole gutted fish decreased from an initial value of 68.55±0.21% to 53.77±2.41% over a period of 13 days of refrigerated storage. Among the treated samples, the CY values for salt treated samples (T1) ranged from 66.70±0.79% to 52.03±0.59% on 13th day of storage with significant lower values of CY as compared to C and T2 samples (p<0.05) (Fig 1). Salt and turmeric treated samples (T2) showed a similar trend in lowering of CY (p<0.05) with a value of 53.17 ± 0.26% on 13th day of storage, which is slightly lower (p<0.05) than the value for control samples on 13th day. The box plot (Fig 2) of the mean values of all the treatments shows high median values for both C and T2 samples. In case of 1%salt and 1% turmeric treated sample (T2) the value of CY is higher than T1 due to addition of turmeric powder with salt, which sustains the cooking of whole gutted rohu during refrigerated storage at 4±1°C.

Table 2: Changes in cooking yield of whole gutted rohu under refrigerated storage.



Fig 1: Plot of Tukey HSD of the changes in cook yield (%) of whole gutted rohu under refrigerated storage (4±1°C).



Fig 2: Box plot of the changes in cook yield (%) of whole gutted rohu under refrigerated storage (4±1°C).


 
Changes in cook loss (CL) of whole gutted rohu under refrigerated storage (4±1°C)
 
The changes in cook loss of whole gutted Rohu samples under refrigerated storage (4±1°C) are given in Table 3 and the increasing trend in cooking loss figures over the days are given in Fig 3. The CL values for the control samples increased from an initial value 31.45±0.02% to 46.23±0.63% over a period of 13 days under refrigerated condition. For T1 samples the CL values increased from 33.30±1.83% to 47.97±1.11% on 13th day of storage with significant higher (p<0.05) figures of cooking loss as compared to the control samples (Fig 4). Plot of Tukey HSD (Fig 4) suggests that T2 samples treated with turmeric and salt showed lower values of cooking loss on day 13 of storage as compared to salt treated samples (T1) with final CL values of 46.83±1.15% on day 13. Box plot of CY (Fig 4) reveals lower median values of cooking loss for T2 samples than both T1 and C samples. During thermal processing of fish, Cook Loss is the most important quality parameter, as it is not only directly related to the organoleptic properties, but also to the appearance of muscle because loss of soluble nutrients and market value of these products are impacted. Cooking loss is generally dependent upon both external factors like heating temperature and time and internal factors which are physical and chemical properties of fish sample.

Table 3: Changes in cook loss of whole gutted rohu under refrigerated storage.



Fig 3: Changes in cook loss of whole gutted rohu under refrigerated storage.



Fig 4: Plot of Tukey HSD and Boxplot diagram of the changes in cook loss (%) of whole gutted rohu under refrigerated storage (4±1°C).


 
Changes in length shrinkage (%) of whole gutted rohu under refrigerated storage (4±1°C)
 
Shrinkage is the common cooking phenomenon which is the ratio between the cooked and uncooked size of the fish. The thermal denaturation of proteins during frying, as described by Oduro (2011), triggers a series of structural changes, including shrinkage of the filament lattice and exposure of hydrophobic areas. These changes promote novel intra- and intermolecular protein interactions, yielding a more compact and denser protein structure. In the present study, the whole gutted rohu samples were expected to undergo shrinkage due to frying like cook loss. As, the whole gutted rohu samples were chosen for study, so shrinkage in total length of fishes is recorded to avoid any anomalies due to shape of whole fish. The changes of length shrinkage in C, T1 and T2 samples are given in Fig 5, 6 and 7. The values were found to increase with storage time at 4±1°C. The lowest shrinkage in total length was observed in T2 samples (p<0.05) on day 13 at 6.74±0.15% which may be attributed to the effect of turmeric combined with salt added to whole gutted Rohu. In case of C, the length shrinkage increased from an initial 4.17±0.14% to 6.98±0.14% and in case of salt treated T1 samples, the shrinkage values increased to 6.95±0.03% on day 13 which was significantly lower (p<0.05) as compared to C (Fig 8).

Fig 5: Plot of the changes in length shrinkage (%) of whole gutted rohu control (C) samples under refrigerated storage (4±1°C).



Fig 6: Plot of the changes in length shrinkage (%) of T1 samples under refrigerated storage (4±1°C).



Fig 7: Plot of the changes in length shrinkage (%) of T2 samples under refrigerated storage (4±1°C).



Fig 8: Plot of Tukey HSD of the changes in length shrinkage (%) of whole gutted rohu under refrigerated storage (4±1°C).



Changes in sensory properties of whole gutted rohu samples under refrigerated storage (4±1°C)
 
Sensory evaluation is a crucial methodology for determining the acceptability of food products, including fish. It involves the scientific assessment of characteristics perceived through the senses of sight, smell, touch, taste and hearing (Mohan et al., 2018). In this study, a trained panel of at least six assessors evaluated the sensory quality of cooked fish using a 9-point hedonic scale, assessing attributes such as color, shape, odor, taste and texture (Bognar, 1998). The scale’s numerical ratings (9-1) corresponded to descriptive categories for each attribute, providing a comprehensive evaluation of the product’s sensory profile. Several evidences were present which showed that assessment of food freshness using organoleptic parameters are capable of giving objective and reliable results when assessments are done under controlled condition. Generally, experienced and trained personnel are required to obtain reliable and reproducible results (Connell, 1990). The changes in the sensory score in three types of samples are recorded in Fig 9, 10 and 11. The sensory score is totally relied on the formula given by Bognar (1998), which comprises the sum of all the organoleptic factors. In Hedonic scale, a high score of (7-9) is acceptable and also below 5 is unacceptable for human consumption. The sensory score of the control sample decreased from an initial value of 12.02±0.03 to 6.00±0.37 over a period of 13 days of refrigerated storage and was above the unacceptable score of 5 till the end.

Fig 9: Plot of the changes in Sensory score of C samples under refrigerated storage (4±1°C).



Fig 10: Plot of the changes in Sensory score of T1 samples under refrigerated storage (4±1°C).



Fig 11: Plot of the changes in Sensory score of T2 samples under refrigerated storage (4±1°C).


       
The T1 samples showed higher sensory scores than C from initial day to 10th day of storage following which the scores declined sharply reaching a value of 5.24±0.34. In case of T2 samples, the value is much higher than other samples. The sensory score decreased from an initial value of 12.85±0.16 to 6.94±0.03. In the present study the sensory scores for all samples were above 5, below which is recommended as unacceptable for human consumption by Bognar (1998).From box plot of sensory scores (Fig 12) the median values of T1 and T2 samples are observed higher than C although the interquartile range for T1 is larger showing the least sensory score below 6. The T2 samples showed high sensory score than the others due to the application of turmeric along with salt. Turmeric has several antimicrobial and antioxidant properties. So, it prevents the spoilage of the fish. Also, turmeric is a good colouring agent, flavour enhancer. As a result, the quality core is high in T2 samples.

Fig 12: Box plot of the changes in sensory quality scores of whole gutted rohu under refrigerated storage (4±1°c).

CONCLUSION

Rohu (Labeo rohita) is a prominent and commercially valuable freshwater fish species in India, with a long history of domestic cultivation, particularly in polyculture system of India. The whole gutted rohu samples are highly perishable and known to deteriorate after death of the fish. This deterioration is caused by lipid oxidation, autolytic degradation and microbial spoilage. Keeping fish fresh is important as it determines the market value of the fish. As a result, it needs proper preservation. In Indian culinary tradition, salt and turmeric have long been employed for fish preservation. The synergy of this combination with refrigerated storage (4±1°C) presents a potentially convenient and economical preservation method. Both these ingredients are antimicrobial in nature and taste enhancers also. Therefore, from the above study it may be concluded that turmeric along with salt treated samples had better storage stability than other two treatments. These ingredients also provide better organoleptic properties to the fish. The results showed significant difference with control sample.

ACKNOWLEDGEMENT

The authors gratefully acknowledge the Department of Fish Processing Technology, Faculty of Fishery Sciences, West Bengal University of Animal and Fishery Sciences, Kolkata, for providing the necessary facilities to conduct this research.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

CONFLICT OF INTEREST

Both the author declares that there are no conflicts of interest for the publication of this article. There is no funding or sponsorship for conducting the research of the present study.

REFERENCES


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  2. Biswas, O. (2024). Evaluation of storage stability and quality changes of fish muscle (Pangasianodon hypothalamus) preserved in fabricated portable solar cooler and domestic refrigerator.  Asian Journal of Dairy and Food Research. 43(2): 313- 319. doi: 10.18805/ajdfr.DR-2075.

  3. Bognar, A. (1998). Comparative study of frying to other cooking techniques influence on the nutritive value. Grasas y Aceites. 49(3-4): 250-260. doi: https://doi.org/10.3989/ gya.1998.v49.i3-4.746.

  4. Connell, J.J. (1990). Methods of assessing and selecting for quality. Control of Fish Quality. 2: 122-150.

  5. El-Bahr, S.M., Korshom, M.A., Mandour, A.E.W.A., El-Bessomy, A.A. and Lebdah, M.A. (2007). The protective effect of turmeric on iron overload   in albino rats. Egyptian Journal of Biochemistry and Molecular Biology. 25(2): ISSN1687-1502.

  6. FAO. (2020). The State of World Fisheries and Aquaculture 2020. Sustainability in action. Rome. https://doi.org/10.4060/ ca9229en.

  7. Jakhar, J.K., Vardia, H.K., Neelmani Chandravanshi, N.C. and Painkra, R.K. (2018). Organoleptic, physiochemical and microbiological qualities of dried fish, tengra (Mystus tengara) with different levels of salt and turmeric powder. 

  8. Kumar, G.S. ,Kumar, G.S., Nayaka, H., Dharmesh, S.M. and Salimath, P.V. (2006). Free and bound phenolic antioxidants in amla (Emblica officinalis) and turmeric (Curcuma longa). Journal of Food Composition and Analysis. 19(5): 446- 452. https://doi.org/10.1016/j.jfca.2005.12.015. 

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    Full Research Article

    Role of Salt and Turmeric in Modulating Cooking and Organoleptic Traits of Whole Gutted Rohu (Labeo rohita) under Refrigerated Storage (4±1°C)

    A
    Ankures Bhattacharya1,*
    0000-0001-5974-5902
    S
    Supratim Chowdhury2
    0000-0002-7166-3093
    1Department of Fish Processing Technology, School of Fisheries, Centurion University of Technology and Management, Paralakhemundi, Gajapati-761 211, Odisha, India.
    2Department of Fish Processing Technology, Faculty of Fishery Sciences, West Bengal University of Animal and Fishery Sciences, Chakgaria, Panchasayar, Kolkata-700 094, West Bengal, India.

    ABSTRACT

    Background: Fish is highly perishable due to rapid microbial and enzymatic spoilage, causing major post-harvest losses, particularly in Rohu (Labeo rohita). Rising concerns over synthetic preservatives have shifted focus toward natural agents like salt and turmeric in organoleptic and cooking qualities.

    Methods: The study aims to assess the cooking qualities likely cooking yield, cooking loss, shrinkage of whole gutted rohu samples during 13 days of refrigerated storage and the organoleptic score by using hedonic score method.

    Result: The results signified that the samples treated with salt and turmeric in combination showed better cooking parameters throughout the 13 days of refrigerated storage and significantly varies with the control and salt treated whole gutted rohu samples. The salt and turmeric treated samples showed the highest cooking yield (53.17%), lowest cooking loss (46.83%) and lowest shrinkage (6.74%) on 13th day of storage. The sensory attributes demonstrated that combined treatment with salt and turmeric significantly preserved the sensory quality and minimized deterioration over the storage period. Turmeric’s antimicrobial and antioxidant properties, along with salt’s dehydration effect, contributed synergistically to maintaining product integrity.

    INTRODUCTION

    The perishable nature of fish underscores its critical role in the livelihoods and nutritional well-being of populations in developing countries. In India, fish is also considered one of the main food for human diet (Biswas, 2024). According to the Food and Agriculture Organization, fish is a staple source of protein for a significant proportion of the global population, with more than 3.3 billion people deriving at least 20% of their annual protein intake from fish and another 1.3 billion people obtaining 15% of their animal protein from this valuable resource (FAO, 2020). The global demand for fish as a source of protein is substantial, with fish accounting for a considerable share of animal protein intake (17%) and overall protein consumption (7%) in 2017. Notably, global fish production has reached unprecedented levels, with an estimated 179 million tonnes produced in 2018. Of this, a significant proportion (156 million tonnes) was directed towards human consumption, resulting in an estimated annual per capita availability of 20.5 kg and highlighting the critical role of fish in meeting global nutritional needs (FAO, 2020). Labeo rohita, known colloquially as Rohu, is a freshwater fish species of paramount importance in Indian aquaculture. With a long history of domestication and a prominent role in traditional carp polyculture systems, Rohu has emerged as a highly sought-after species, driven by its desirable characteristics and strong market demand. Generally, it is found in India, Bangladesh, Myanmar and Pakistan (Talwar and Jhingran, 1991). In India Rohu has been transplanted into all the rivers of Northern, Central and Eastern part and also introduced in some river of the peninsular India and Srilanka. Rohu is an omnivorous fish coming under family Cyprinidae and order Cypriniformes is extensively used in aquaculture. It is highly preferred for culture and contributes more than 80% of the major carp culture in India. Traditionally, the Indian cuisine uses turmeric and salt for preservation of fish. Among the traditional practices, curing is one of the old, convenient method for preserving fish by reducing the spoilage (Jakhar et al., 2018). Both these ingredients are antimicrobial in nature and taste enhancers. Turmeric additionally has antioxidant properties. Salt is one of the oldest natural preservatives used to prevent the spoilage taking place in storing the fish. Salt has its antimicrobial, antibacterial, biochemical activity, which makes it widely usable preservatives. Salt, generally the common salt (NaCl) is used that penetrates the tissue. Salt inhibits the growth of microorganisms by removing water out of the microbial cells by osmosis. Salt lowers the moisture content of the fish to a level where any bacterial process and enzymatic activity cannot occur, as a result the cell collapse itself. This is the antimicrobial activity of salt. In addition of salt’s suppressing effect on food spoilage bacteria, salt has antibacterial activities against various food borne pathogens like Clostridium botulinum. (Sallam, 2007). High concentration of salt also can cause myofibrils contraction and protein dehydration. Use of salt as preservative can improve the sensory attributes of final fish and also improve texture and prolong shelf life of fish.
           
    Turmeric, a herb of Zingiberaceae family is a good source of natural antioxidant and antimicrobial agent (Negi et al., 1999; Kumar et al., 2006). Also, Turmeric is used in as natural preservative to suppress the growth of several pathogenic bacteria. Turmeric antibacterial activity can inhibit Clostridium botulinum and other gram-positive bacteria like Bacillus subtilis. Turmeric helps to improve the meat quality of fish and also decrease the microbial load in fish. It is one of the most widely used as an antiseptic, anticancer agent. It also reduces the biogenic amine formation in fish during the chilled storage and reduces the foul odor during prolonged storage in refrigerated condition and increase the shelf life of fish. Turmeric also controls other biochemical parameters and help to preserve the fish in good condition. Curcumin, the active component of Turmeric is a potent antioxidant (El-Bahr et al., 2007) and has hepatoprotective properties. Turmeric contains turmerin, a water-soluble peptide that exhibits potent antioxidant activity, effectively scavenging free radicals and terminating oxidative chain reactions. Turmeric also has antiperoxidant activity on several natural fish lipids and also reduces the level of lipid peroxides. It is a potent inhibitor of lipid peroxidation.  Turmeric is also used in food processing industry as additives for pigmentation and flavor enhancement (Sirisidthi et al., 2016). Turmeric also improves sensory quality of fish and making it acceptable towards the panelists. Turmeric is known as natural dye, the pigment component of turmeric, Curcumin helps to maintain and improve the color of fish. Turmeric also improves the texture, flavor and aroma of fish. Due to this reason, turmeric is widely used in house hold before cooking and also during storage of fish.
           
    In the present study the influence of turmeric and salt addition on the quality parameters of whole, gutted rohu was evaluated under refrigerated condition. Refrigeration, salt and turmeric are expected to offer a series of hurdles to microbial growth and hence retard the spoilage process. Apart from hurdle technology turmeric is expected to act as an antioxidant and both the additives may improve the shelf life of the whole gutted rohu under refrigerated storage.

    MATERIALS AND METHODS

    Raw material
     
    Fresh Rohu, locally known as Rui or Rohu (Labeo rohita) was brought from Parijoy Fish Farm, Naihati, North 24 Parganas during the month of July, 2020 selected through simple random sampling for inclusion in this study. These freshly harvested fishes were carefully transferred in insulated box under iced condition transported to the Fish Processing Technology Laboratory, Faculty of Fisheries Sciences, within 1-2 hours of collection.
     
    Fish processing
     
    Immediately after transferring the samples into laboratory, they were washed thoroughly in running water to remove the dirt, slime and other physical substances. After washing the samples were beheaded, eviscerated and descaled manually following which fishes were prepared weighting about 70-100 g under strict adherence to hygienic and sanitary protocols to minimize the risk of cross-contamination.
     
    Incorporation of preservatives and storage study
     
    Processed fishes are divided into three parts like, C, T1 and T2. First part was taken as Control (C) without any treatment. Sample T1 and T2 were mixed with salt (1% NaCl) and salt and Turmeric (1% salt +1% turmeric) respectively. After that, samples were stored under refrigerated condition maintained at a temperature of 4±1°C.
     
    Estimation of cooking properties
     
    Cooking loss
     
    The extent of cooking loss was quantified according to the method described by Niamnuy et al., (2008), wherein the mass difference between raw and cooked fish steaks was measured and calculated. Each sample was cooked on a frying pan with hot oil and the oil temperature was at 150°C for 7 mins. Post-cooking, samples were cooled to room temperature and reweighed to determine cooking loss, calculated as follows:

     
    Cooking yield
     
    The cooking yield of fish was assessed according to the methodology outlined by Aleson-Carbonell et al. (2005). Samples were cooked in a frying pan with hot oil at 150°C for 7 minutes. Following cooking, samples were cooled to room temperature and subsequently reweighed to determine yield.

     
    Shrinkage
     
    Shrinkage (%) was calculated as by simple mathematical formula and this was calculated from the difference in the length, width and height of fish fillet before and after cooking method. Each sample was cooked on a frying pan with refined sunflower oil and the oil temperature was at 160°C for 4 mins. After cooking the samples were cooled down to room temperature and then took the length, width and height of fish fillet. The shrinkage was calculated as follows:

     
    Here,
    L = Length before cooking.
    L1 = Length after cooking.
     
    Sensory evaluation
     
    Sensory evaluation of cooked fish was conducted by a panel of at least 6 experienced assessors at regular intervals during storage. The panellists assessed the samples based on a comprehensive set of attributes, including colour, shape, odour, taste and texture, utilizing a 9-point hedonic scale (Bognar, 1998). The scale’s numerical ratings (9-1) corresponded to specific descriptive categories for each attribute (Table 1).

    Table 1: Descriptions of 9-point hedonic scale.



    The sensory quality was calculated by following equation:

     
    Where,
    Fi = Colour (browning).        
    F2 = Shape.
    G = Odour + taste.
    T = Texture.
     
    Statistical analysis
     
    Prior to analysis, data were verified for normal distribution using normality plots. One-way analysis of variance (ANOVA) was then performed to identify significant differences among means at a significance level of α = 0.05. Statistical analyses were conducted using Microsoft Office Excel 2007 and R software (Version 2.14.1). Post-hoc comparisons were made using Tukey’s honest Significant Difference (HSD) test to determine significant differences between treatment groups.

    RESULTS AND DISCUSSION

    Cook yield (CY) of whole gutted rohu under refrigerated storage (4±1°C)
     
    The changes in cook yield of whole gutted Rohu samples under refrigerated storage (4±1°C) are given in Table 2. A decreasing trend was found in cooking yield percentage for all samples during the 13 days of investigation. The cooking yield values for the control (C) whole gutted fish decreased from an initial value of 68.55±0.21% to 53.77±2.41% over a period of 13 days of refrigerated storage. Among the treated samples, the CY values for salt treated samples (T1) ranged from 66.70±0.79% to 52.03±0.59% on 13th day of storage with significant lower values of CY as compared to C and T2 samples (p<0.05) (Fig 1). Salt and turmeric treated samples (T2) showed a similar trend in lowering of CY (p<0.05) with a value of 53.17 ± 0.26% on 13th day of storage, which is slightly lower (p<0.05) than the value for control samples on 13th day. The box plot (Fig 2) of the mean values of all the treatments shows high median values for both C and T2 samples. In case of 1%salt and 1% turmeric treated sample (T2) the value of CY is higher than T1 due to addition of turmeric powder with salt, which sustains the cooking of whole gutted rohu during refrigerated storage at 4±1°C.

    Table 2: Changes in cooking yield of whole gutted rohu under refrigerated storage.



    Fig 1: Plot of Tukey HSD of the changes in cook yield (%) of whole gutted rohu under refrigerated storage (4±1°C).



    Fig 2: Box plot of the changes in cook yield (%) of whole gutted rohu under refrigerated storage (4±1°C).


     
    Changes in cook loss (CL) of whole gutted rohu under refrigerated storage (4±1°C)
     
    The changes in cook loss of whole gutted Rohu samples under refrigerated storage (4±1°C) are given in Table 3 and the increasing trend in cooking loss figures over the days are given in Fig 3. The CL values for the control samples increased from an initial value 31.45±0.02% to 46.23±0.63% over a period of 13 days under refrigerated condition. For T1 samples the CL values increased from 33.30±1.83% to 47.97±1.11% on 13th day of storage with significant higher (p<0.05) figures of cooking loss as compared to the control samples (Fig 4). Plot of Tukey HSD (Fig 4) suggests that T2 samples treated with turmeric and salt showed lower values of cooking loss on day 13 of storage as compared to salt treated samples (T1) with final CL values of 46.83±1.15% on day 13. Box plot of CY (Fig 4) reveals lower median values of cooking loss for T2 samples than both T1 and C samples. During thermal processing of fish, Cook Loss is the most important quality parameter, as it is not only directly related to the organoleptic properties, but also to the appearance of muscle because loss of soluble nutrients and market value of these products are impacted. Cooking loss is generally dependent upon both external factors like heating temperature and time and internal factors which are physical and chemical properties of fish sample.

    Table 3: Changes in cook loss of whole gutted rohu under refrigerated storage.



    Fig 3: Changes in cook loss of whole gutted rohu under refrigerated storage.



    Fig 4: Plot of Tukey HSD and Boxplot diagram of the changes in cook loss (%) of whole gutted rohu under refrigerated storage (4±1°C).


     
    Changes in length shrinkage (%) of whole gutted rohu under refrigerated storage (4±1°C)
     
    Shrinkage is the common cooking phenomenon which is the ratio between the cooked and uncooked size of the fish. The thermal denaturation of proteins during frying, as described by Oduro (2011), triggers a series of structural changes, including shrinkage of the filament lattice and exposure of hydrophobic areas. These changes promote novel intra- and intermolecular protein interactions, yielding a more compact and denser protein structure. In the present study, the whole gutted rohu samples were expected to undergo shrinkage due to frying like cook loss. As, the whole gutted rohu samples were chosen for study, so shrinkage in total length of fishes is recorded to avoid any anomalies due to shape of whole fish. The changes of length shrinkage in C, T1 and T2 samples are given in Fig 5, 6 and 7. The values were found to increase with storage time at 4±1°C. The lowest shrinkage in total length was observed in T2 samples (p<0.05) on day 13 at 6.74±0.15% which may be attributed to the effect of turmeric combined with salt added to whole gutted Rohu. In case of C, the length shrinkage increased from an initial 4.17±0.14% to 6.98±0.14% and in case of salt treated T1 samples, the shrinkage values increased to 6.95±0.03% on day 13 which was significantly lower (p<0.05) as compared to C (Fig 8).

    Fig 5: Plot of the changes in length shrinkage (%) of whole gutted rohu control (C) samples under refrigerated storage (4±1°C).



    Fig 6: Plot of the changes in length shrinkage (%) of T1 samples under refrigerated storage (4±1°C).



    Fig 7: Plot of the changes in length shrinkage (%) of T2 samples under refrigerated storage (4±1°C).



    Fig 8: Plot of Tukey HSD of the changes in length shrinkage (%) of whole gutted rohu under refrigerated storage (4±1°C).



    Changes in sensory properties of whole gutted rohu samples under refrigerated storage (4±1°C)
     
    Sensory evaluation is a crucial methodology for determining the acceptability of food products, including fish. It involves the scientific assessment of characteristics perceived through the senses of sight, smell, touch, taste and hearing (Mohan et al., 2018). In this study, a trained panel of at least six assessors evaluated the sensory quality of cooked fish using a 9-point hedonic scale, assessing attributes such as color, shape, odor, taste and texture (Bognar, 1998). The scale’s numerical ratings (9-1) corresponded to descriptive categories for each attribute, providing a comprehensive evaluation of the product’s sensory profile. Several evidences were present which showed that assessment of food freshness using organoleptic parameters are capable of giving objective and reliable results when assessments are done under controlled condition. Generally, experienced and trained personnel are required to obtain reliable and reproducible results (Connell, 1990). The changes in the sensory score in three types of samples are recorded in Fig 9, 10 and 11. The sensory score is totally relied on the formula given by Bognar (1998), which comprises the sum of all the organoleptic factors. In Hedonic scale, a high score of (7-9) is acceptable and also below 5 is unacceptable for human consumption. The sensory score of the control sample decreased from an initial value of 12.02±0.03 to 6.00±0.37 over a period of 13 days of refrigerated storage and was above the unacceptable score of 5 till the end.

    Fig 9: Plot of the changes in Sensory score of C samples under refrigerated storage (4±1°C).



    Fig 10: Plot of the changes in Sensory score of T1 samples under refrigerated storage (4±1°C).



    Fig 11: Plot of the changes in Sensory score of T2 samples under refrigerated storage (4±1°C).


           
    The T1 samples showed higher sensory scores than C from initial day to 10th day of storage following which the scores declined sharply reaching a value of 5.24±0.34. In case of T2 samples, the value is much higher than other samples. The sensory score decreased from an initial value of 12.85±0.16 to 6.94±0.03. In the present study the sensory scores for all samples were above 5, below which is recommended as unacceptable for human consumption by Bognar (1998).From box plot of sensory scores (Fig 12) the median values of T1 and T2 samples are observed higher than C although the interquartile range for T1 is larger showing the least sensory score below 6. The T2 samples showed high sensory score than the others due to the application of turmeric along with salt. Turmeric has several antimicrobial and antioxidant properties. So, it prevents the spoilage of the fish. Also, turmeric is a good colouring agent, flavour enhancer. As a result, the quality core is high in T2 samples.

    Fig 12: Box plot of the changes in sensory quality scores of whole gutted rohu under refrigerated storage (4±1°c).

    CONCLUSION

    Rohu (Labeo rohita) is a prominent and commercially valuable freshwater fish species in India, with a long history of domestic cultivation, particularly in polyculture system of India. The whole gutted rohu samples are highly perishable and known to deteriorate after death of the fish. This deterioration is caused by lipid oxidation, autolytic degradation and microbial spoilage. Keeping fish fresh is important as it determines the market value of the fish. As a result, it needs proper preservation. In Indian culinary tradition, salt and turmeric have long been employed for fish preservation. The synergy of this combination with refrigerated storage (4±1°C) presents a potentially convenient and economical preservation method. Both these ingredients are antimicrobial in nature and taste enhancers also. Therefore, from the above study it may be concluded that turmeric along with salt treated samples had better storage stability than other two treatments. These ingredients also provide better organoleptic properties to the fish. The results showed significant difference with control sample.

    ACKNOWLEDGEMENT

    The authors gratefully acknowledge the Department of Fish Processing Technology, Faculty of Fishery Sciences, West Bengal University of Animal and Fishery Sciences, Kolkata, for providing the necessary facilities to conduct this research.
     
    Disclaimers
     
    The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

    CONFLICT OF INTEREST

    Both the author declares that there are no conflicts of interest for the publication of this article. There is no funding or sponsorship for conducting the research of the present study.

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