The study was conducted to find the effectiveness of bio-preservatives and packaging method on the shelf life of milk solids based khoa. Khoa samples were prepared individually by combinations of SMP (skimmed milk powder) with ghee and whey protein concentrates and SMP with cream (50% fat). The control sample was prepared utilizing full cream buffalo milk (6% fat). Natamycin at 10 ppm and nisin at 100 IU/g were incorporated while khoa was still hot (85-90°C). The samples without biopreservatives were packaged in simple and vacuum packaging separately. The all treatments were evaluated for sensory quality during storage at room temperature (23±2 °C). The study revealed that vacuum packaged and bio-preservatives treated samples were organoleptically acceptable up to 20th day storage.
HIGHLIGHTS
Khoa can be very well prepared using milk solids.
Bio-preservatives and vacuum packaging increase the shelf life of khoa.
India has made significant progress in milk production and has emerged as the highest milk producing country in the world. India’s annual milk production during 201617 was 165.4 million tonnes (DAHDF, Annual Report 2018, India). Approx. 50% of the total milk produced is converted to various traditional dairy products (Prasad et al., 2012). Conversion of liquid milk into traditional dairy products increases the longevity of milk solids. Traditional milk products which are converted from milk in order to preserve the milk solids in a concentrated form for extended period play a significant role in the economic, social, religious and nutritional values of the Indian masses from the time immemorial. As per Food Safety and Standards Authority of India (FSSAI, 2011) khoa by whatever variety of names it is sold such as pindi, danedar, dhap, mawa or kava means the product obtained from cow or buffalo or goat or sheep milk or milk solids or a combination thereof by rapid drying. About six lakh tonnes of khoa is being manufactured annually, mostly in private and unorganized sectors of India by utilizing about 7% of the total milk produced (Kumar, 2013). Khoa is a major intermediate base for a variety of sweets like burfi, peda, kalakand, gulabjamun etc. (Soumya et al., 2015). The regional and seasonal imbalances in milk production in India call for developing suitable technology for efficient use of surplus milk solids.
Food spoilage refers to the damage of the original nutritional value, texture and flavor of the food that eventually render food harmful to people and unsuitable to eat. Milk based sweets during storage undergo several physical, biochemical and microbiological changes making them unfit for human consumption (Londhe et al., 2012). Microbes may gain entry into food at any stage of processing right from the farm to till the food is reached to the final consumer like at the time of packaging, transport and storage etc, so it becomes imperative not only to take all kinds of preventive measures but also to evaluate at every stage (Agarwal and Rachappa, 2006).
How to cite this article: Vaquil, Bhardwaj, P.K., Kumar, S. and Yadav, S. (2021). Impact of bio-preservatives on sensory quality of milk solids incorporated khoa stored at room temperature (23±2°C). J. Anim. Res.,11(1): 173-180. Source of Support: None; Conflict of Interest: None The deteriorating agents of the food quality are oxygen contained in the air and microorganisms such as bacteria and moulds. Oxygen promotes several types of deteriorative reactions in foods including oxidation of fat, browning and pigment oxidation and is the key element required for the growth of common spoilage bacteria and fungi. Therefore, to increase the shelf life of foods, the package atmosphere should contain a low concentration of residual oxygen (Sandhya, 2010). In order to achieve improved food safety against pathogens, food industry makes use of chemical preservatives. But, these chemicals have many drawbacks, which include their proven toxicity, alteration of the organoleptic and nutritional properties of foods and recent consumer demands for safe and minimally processed products without additives. Thus, to harmonize consumer demands with the necessary safety standards, traditional means of controlling microbial spoilage and safety hazards in foods are being replaced by combinations of innovative technologies that include biological antimicrobial systems such as lactic acid bacteria (LAB) and/or their metabolites (Nath et al., 2013). In addition, the absence of proper packaging, the rate of chemical deterioration of khoa such as oxidation and browning increase. But, use of antioxidant, antimicrobial agent and packaging increase the shelf- life of Khoa.
The concentration of natamycin for yoghurt preservation has been suggested to be in the range of 5-10 ppm (Thomas and Delves, 2001). The use of natamycin as a natural preservative in dairy products and other foods has been approved in over sixty countries (Delves et al., 2005). The use of nisin as bio-preservative has been widely investigated in a large variety of fresh and processed foods (Jung et al., 1992). It is effective against several pathogenic Gram-positive bacteria such as Listeria monocytogenes and C. botulinum, but also against some Gram-negative pathogens such as Escherichia coli and Salmonella spp. Keeping above points in view, this study was carried to develop bio-preservative incorporated milk solid based khoa and subjected to vacuum packaging as well and study their effect on organoleptic quality during storage at 23±2 °C.
MATERIALS AND METHODSPlace of Study
The present study was conducted in the Department of Livestock Products Technology, College of Veterinary Sciences, LUVAS, Hisar to develop khoa by utilizing milk solids and subsequent impact of packaging methods and bio-preservatives to enhance the shelf-life at room temperature (23±2 °C).
Procurement of raw materials
Ghee, cream (50% fat) and full cream buffalo milk (6% fat) were procured from experimental dairy plant, Department of LPT, LUVAS, Hisar. Skim milk powder (SMP), whey protein concentrates and low density polyethylene (LDPE) pouches were procured from local market.
Bio-preservative
Nisin was procured from Hi Media Laboratories and Natamycin from Sigma-Aldrich.
Preparation of khoa using milk solids
Khoa was standardized for fat by Pearson’s square method as described by De (2004) to meet legal standard of fat (20% fat on fresh basis and 30% fat on dry basis). Khoa samples were prepared separately by combinations of SMP with ghee and whey protein concentrates and SMP with cream (50% fat).
For ghee based khoa; 680 g SMP (13.6%), 300 g ghee (6%) and 20 g (0.4%) pre-standardized whey protein concentrates were mixed and hot water (80%) was added to make total weight 5 kg. Similarly, for cream based khoa; 500g SMP (10%) + 480 g cream (9.6%) were mixed and hot water (80.4%) added to make total weight 5 kg. Proper mixing and filtration was done followed by preheating at 65°C. Then homogenization (double stage) and desiccation was carried out in gas operated semiautomatic machine. The control khoa sample was prepared utilizing full cream buffalo milk (6% fat).
Addition of bio-preservatives
Natamycin at 10 ppm (Rabee and Heba, 2017) and nisin at 100 IU/g (Gupta et al., 1989) were added while khoa was still hot (about 85-90 °C). Proper mixing was done in machine.
Packaging
Bio preservatives added khoa samples were simply packaged in LDPE bag and sealed with sealing machine. The samples without bio-preservative were packaged in two different packaging techniques i.e. simple packaging and vacuum packaging.
Sensory quality evaluation
Analysis of sensory quality of developed khoa samples was performed by using the nine point hedonic scale (Nelson and Trout, 1964) (Table 1). A semi trained panel evaluated the sensory attributes viz. color and appearance, flavor, and overall acceptability at regular interval of 5 days at room temperature (23±2 ° C).
Scores under 9 point hedonic scale
Statistical analysis
Data was analyzed statistically on ‘SPSS-16.0’ (SPSS Inc., Chicago, II USA) software package as per standard methods (Snedecor and Cochran, 1994). The statistical significance was estimated at 5% level (P≤0.05) and evaluated with Duncan’s Multiple Range Test.
RESULTS AND DISCUSSIONColor and appearance
Color and appearance score of khoa stored at room temperature ranged from 8.25 to 8.50 (i.e. all treatments liked very much) on 0th day, however all values were found statistically similar to each other (Table 2). On every interval of storage there was continuous decrease in the color and appearance scores of all samples.
On 5th day the highest value of color and appearance score was reported in C2 (8.00) and lowest value in T5 (7.67). On 10th day of storage color and appearance scores ranged 6.92 to 7.33. There was no significant difference in color and appearance scores of all treatments on particular day till 15th day of storage. But on 20th day, T5 had score 6.00 which was found significantly (P≤0.05) lower than that of C2 (6.75), C3 (6.83), C4 (6.75), T3 (6.67) and T4 (6.58). However the all treatments were slightly liked till the 20th day of storage at room temperature. Sensory evaluation was not performed on 25th day due to visible spoilage of sample.
There was significant decrease in color and appearance scores of khoa with advancement of storage period. This might be due to microbial growth (yeast and moulds), known to be responsible for discoloration and lipolytic defects in khoa (Goyal and Srinivasan, 1984). Microbial contamination produces undesirable effects e.g. change in color, odour, taste and texture of the products. Jain et al. (2015) and Acharya and Agrawal (2010) also reported decrease in sensory score of kalakand and khoa, respectively during storage at 25°C. Although, every treatment had sensory score more than 6 (i.e. slightly liked) till 20th day of storage. All natamycin treated khoa samples had higher color and appearance scores which might be due to lower yeast and mould counts by caused by bio-preservatives.
The khoa samples which were packaged under vacuum condition had better color and appearance score than simple packaged sample. This might be because of the reason that vacuum packaging did not allow atmospheric factors to distort the color and appearance of khoa. Kumar et al. (2010) also noticed the higher color and appearance score in vacuum packaged khoa than simple packaged khoa. Khoa samples prepared by using milk solids had slightly lower color and appearance score as compare to buffalo milk based khoa. Voghra and Rajoria (1983) also reported lower color score for khoa prepared from milk powder than buffalo milk khoa.
Color and appearance scores of khoa at room temperature (23±2°C) (Mean±S.E., n=12)
Body and texture
Sensory panelist awarded body and texture scores more than 8 (i.e. liked very much) to all treatments on 0th day of storage (Table 3). There was no significant difference in body and texture scores on that day. Body and texture scores of all treatment ranged 7.75 to 8.05 on 5th day of storage. On 10th day C3 (7.67) had highest value while T5 (7.25) had lowest body and texture scores, this showed moderate acceptance of all samples on that day.
Till 15th day, body and texture scores of all treatment were found statistically similar to each other on every particular day of storage. But on 20th day of storage, body and texture score of T5 (6.08) was observed significantly (P≤0.05) lower than C2 (6.75), C3 (6.83), C4 (6.75) and T3 (6.75). All stored sample have body and texture scores more than 6, this indicated that all sample were liked slightly on 20th day. But khoa samples were not subjected to sensory evaluation due to visibly spoilage of samples on 25th day storage.
There were significant decreases in color and appearance scores of khoa in each treatment with time during storage. This might be due to increase in microbial counts during storage. Microbial contamination produced undesirable effects e.g. change in color, odour, taste and texture of the product (Goyal and Srinivasan, 1984). The results were in agreement with Acharya and Agrawal (2010) and Jain et al. (2015), who also reported significant decrease in body and texture score of khoa and kalakand, respectively during storage at 25ºC. However, body and texture of all treatments did not differ significantly on same day of storage. Every treatment had sensory score more than 6 (i.e. slightly liked) till end of 20th day of storage.
All natamycin treated khoa samples had higher body and texture scores, which might be owing to lower yeast and mould counts. Those khoa samples which were packaged under vacuum condition also had better body and texture score than simple packaged samples, which might be because of the reason that it did not allow atmospheric factors to distort the color and appearance of khoa. Kumar et al. (2010) also noticed higher body and texture score in vacuum packaged khoa than simple packaged khoa. The samples developed by using milk solids had slightly lower body and texture score as compared to full cream buffalo milk khoa. Voghra and Rajoria (1983) also reported lower body and texture score for khoa prepared from milk powder than buffalo milk khoa.
Body and texture score of khoa at room temperature (23±2°C) (Mean±S.E., n=12)
Flavor score of khoa at room temperature (23±2°C) (Mean±S.E., n=12)
Flavor
There were non-significant differences in flavor scores of all treatment on 0th day of storage and similar trend were observed till the 10th day of storage at room temperature (Table 4). On 5th day of storage flavor scores ranged 7.67 to 7.92, although all value differed non-significantly. Sensory panelist awarded highest flavor score to C3 (7.58) and scores ranged 7.17 to 7.58 on 10th day of storage.
On 15th day, flavor score of C3 (7.33) was found significantly (P≤0.05) higher than T5 (6.75). Scores for each sample were observed more than 7 except T1 (6.92), T5 (6.75) and T8 (6.92). According to flavor score all khoa samples were liked moderately except three samples (T1, T5 and T8) those were liked slightly.
Flavor scores of all treatments ranged 5.83 to 6.83 on 20th day. Flavor scores of C3 were reported significantly (P≤0.05) higher than T1 (6.17), T5 (5.83), T6 (6.00), T7 (6.25) and T8 (6.17). Hence, depending on flavor score, all samples were liked slightly by sensory panel except T5 which was neither liked nor disliked. Sensory evaluation was not performed on 25th day due to visible spoilage of sample.
There were significant decreases in flavor scores of khoa in each treatment during storage time. That might be due to increase in microbial counts during storage. Microbial contamination produces undesirable effects e.g. change in color, odour, taste and texture of the product (Goyal and Srinivasan, 1984). Jain et al. (2015) and Acharya and Agrawal (2010) also reported decrease in flavor scores of kalakand and khoa, respectively during storage at 25ºC. Every treatment had sensory score more than 6 (i.e. slightly liked) at end of 20th day of storage. All natamycin treated khoa samples had higher flavor score, which might be due to lower yeast and mould counts.
Those khoa samples which were packaged under vacuum condition had better flavor score than simple packaged samples. That might be because of the reason that it did not allow atmospheric factors to distort the flavor of khoa. Kumar et al. (2010) also noticed the higher color and appearance score in vacuum packaged khoa than simple packaged khoa. Khoa samples prepared by using milk solids had slightly lower flavor score as compared to buffalo milk khoa. Voghra and Rajoria (1983) also reported lower flavor score for khoa prepared from milk powder than buffalo milk khoa.
Overall acceptability
Sensory panelist awarded highest overall acceptability scores to C2 (8.50) while lowest to T7 (8.17) on 0th day of storage (Table 5). Overall acceptability scores of all treatments were found more than 8 (i.e. liked very much). On each particular interval of storage overall acceptability score of all treatments differed non-significantly and that trend remained same till 15th day of storage. However, the overall acceptability scores were decreased continuously during the storage period.
On 5th day the overall acceptability score ranged 7.58 to 8.00. Overall acceptability score of T5 was found lowest which differed non-significantly to all treatments. Overall acceptability score of all khoa samples were found more than 7 (i.e. liked moderately) on 10th day of storage. Sensory panelist awarded the highest score to C3 (7.67) and lowest to T5 (7.25). On 15th day the overall acceptability scores of khoa samples ranged 6.92 to 7.33. C3 (7.33) had highest while T5 (6.92) had lowest score but all value differed non-significantly.
Sensory panelist awarded overall acceptability scores ranged 5.92 to 6.92 on 20th day during storage study. Overall acceptability score of C3 (6.92) was found significantly (P≤0.05) higher than C1 (6.33), T1 (6.17), T5 (5.92), T6 (6.08), T7 (6.33) and T8 (6.17). Depending on overall acceptability score, all khoa samples were liked slightly except T5 on 20th day of storage. But on 25th day all samples were found spoiled, so not subjected to sensory evaluation.
There were significant decreases in overall acceptability scores in each treatment during storage period. This might be due to microbial growth responsible for discoloration and lipolytic defects in khoa (Goyal and Srinivasan, 1984). Microbial contamination produces undesirable effects e.g. change in color, odour, taste and texture of the product.
Overall acceptability score of khoa at room temperature (23±2°C) (Mean±S. E., n=12)
Jain et al. (2015) and Acharya and Agrawal (2010) also reported decrease in sensory score of kalakand and khoa, respectively during storage at 25°C. However, overall acceptability of all treatments did not differ significantly on same day of storage. Every treatment had sensory score more than 6 (i.e. slightly liked) at end of 20th day of storage.
All natamycin and nisin treated samples had higher overall acceptability scores, which might be due to lower yeast and mould counts. Those khoa samples which were packaged under vacuum conditions had better overall acceptability score than simple packaged sample. This may be because of the reason that it did not allow atmospheric factors to distort the sensory properties of khoa. Kumar et al. (2010) and Sharma et al. (2001) also revealed higher overall acceptability score in vacuum packaged khoa than simple packaged khoa. The samples developed by using milk solids had slightly lower overall acceptability scores as compared to full cream buffalo milk based khoa. Voghra and Rajoria (1983) also reported lower color score for khoa prepared from milk powder than buffalo milk khoa.
CONCLUSION
The present study revealed that the milk solids (SMP, cream and ghee) could be very well used to prepared khoa which was comparable to from full cream buffalo milk based khoa and also met the legal standards. Natamycin at the levels of 10 ppm and nisin at 100 IU/g were found equally effective in extending shelf-life of khoa. In addition, vacuum packaging also significantly maintained sensory quality. Bio-preservative treated and vacuum packaged khoa samples were organoletically acceptable up to 20 days at room temperature (23±2 °C).
ACKNOWLEDGEMENTS
The authors are thankful to Head of Department, Department of Livestock Products Technology, College of Veterinary Sciences, Lala Lajpat Rai University of Veterinary & Animal Sciences, Hisar for providing necessary facilities.
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