By Mina Seifzadeh, Iranian Fisheries Science Research Institute
This research investigates the effects of whey protein coating on the chemical, bacterial, and sensory properties, proximate analysis, and shelf life of common kilka during frozen storage.
For this experiment, common kilka were coated with 9% whey protein while non-coated kilka were used as a control sample. Both the coated and non-coated samples were stored at -18 oC for six months. Results showed that total bacterial counts (1.47–2.49 log CFU/g) and Staphylococcus bacteria (1.02–1.71 log CFU/g) were lower in the coated samples compared to the control samples (P > 0.05). Coliform, E. coli, and Pseudomonas bacterial contamination were undetectable in both the coated and control samples throughout the storage period. Humidity (73.92–46.18%), protein (18.24–19.07%), lipid (4.27–4.01%), ash (1.82–2.12%), and calorie (108.85–120.78 kcal/kg) were higher in the test samples compared to the control samples. Values for peroxide (0.15–5.12 meq/kgoil), free fatty acids (1.32–12.40 g/100), thiobarbituric acid (0.14–0.98 mg/kg), total volatile basic nitrogen (TVB-N) (6.32-21.79 mg/100g), and pH (6.32-7.45) were lower in the test samples.
Significant decreases in chemical factors were observed in the coated samples compared to the control samples (p<0.05). The overall acceptance score had a better quality in the coated samples (80) compared to the control samples (113) (p<0.05). According to the results of experiments and statistical analysis, the coated samples had a favorable quality until the end of the storage period but the control samples had lost their quality. Therefore, a 9% whey protein coating is recommended for kilka fish as a better alternative to using disposable packaging dishes with a cellophane coating.
Introduction
Kilka fish belong to the genus Clupeonella, in the family Clupeidae. These fish are composed of three species consisting of Clupeonalla delicatula, C. engrauliformis, and C. grimmi (Coad, 2017). They can be processed into salted, smoked, pickled conserved, dried, and frozen fish. In Iran, kilka products are sold fresh, canned, or in frozen packaging. From 2016 to 2021, the annual catch ranged from 20,138 to 22,429 tons. Approximately 10-12% of this catch was used for human consumption, and the remaining 88-90% was used for animal feeds. 6,307 – 6,626 tons of the fish were caught in the Guilan Province, of which 5-12% was used for human consumption and the remaining 88-95% for animal feeds (Program and Budget Office, 2022). Consumption of fresh kilka fish dropped from 6% to 2.20% during the period of 2004 to 2009. Consumption of canned kilka also dropped during the same period, whereas consumption of frozen kilka rose during the same years (Seifzadeh, 2014). The frozen fish packs had a much higher sales rate in comparison to the sales of fresh fish because of their longer storage time and wider distribution. Sales of frozen fish were also higher. The fish packs were frozen for less than three months because longer frozen-storage time may lead to color changes, surface dryness, and peroxide accumulation. Even so, the first indication of a decline in quality after only one month of frozen storage was a reduction in the weight of frozen packed fish, which in turn had a deteriorating effect on the texture and taste of the small-sized fish. There was a 3.5% decline in fish weight after three months of frozen storage (Moeini, 2009).
Kilka fish, which have valuable protein and digestible fats, rich vitamins, and minerals, have attained an important position in the food-product market. Overall, the value of food products, such as kilka, depends on their nutritional specifications and acceptability in society; therefore, accurate processing and the preparation of appealing product varieties are crucial for the market (Khanipor et al., 2017).
The final step of the food-production chain is packaging, which occupies the middle ground of production, distribution, and consumption. Many small and large companies all over the world are very active in packaging industry. Competition among packaging manufacturers has led to improved quality and more types of packaging. Currently, numerous packaging and preservation methods, including nonbiological decomposable synthetic chemicals, are used for food preservation. Recently, new packaging materials—such as edible films that are biologically decomposable—have entered the market (Aguilar-Rivera et al., 2023; Kandasamy et al., 2018).
Consumer demand is high for high-quality seafood products, especially those that can retain their superior quality of taste, texture, and general fresh appearance following a prolonged period of cold or frozen storage (Bayram et al., 2021). The use of edible films for packaging kilka seems to be an ideal method for proper preservation during periods of long storage.
Edible coatings are completely water soluble and glossy; they perform just like a secondary skin and have favorable properties such as rapid attachment to foodstuff, label attachment, antibacterial, and antioxidant properties (Seifzadeh, 2022). These types of coatings protect the aroma, taste, and food color as well as help to maintain the nutritional components. Coating food products with these films can lead to preservation of food moisture and the lowering of oxygen absorption, which can substantially improve the appearance of food products. These coatings are invisible to the naked eye (Londoño-Hernandez et al., 2018; Yu et al., 2019).
Whey protein is derived from milk and is composed of protein, lactose, and inorganic salts. It is anti-bacterial, antiproteolysis, and preserves food moisture (Setiadi and Sauria, 2020). Edible films made of whey protein have been used for packaging salmon, hotdogs, sausages, crackers, and frozen fish filets, and have improved their quality and shelf life (Seifzadeh, 2014). The objective of this study is to investigate the effects of a whey protein coating on the chemical, bacterial, and sensory properties, proximate analysis, and shelf life of frozen kilka.
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