Introduction
Silver carp (Hypophthalmichthys molitrix), owing to its easy accessibility and lower cost compared to marine fish, presents economic opportunities for developing by-products (Ojagh et al., 2018). The introduction of fish nuggets, with their desirable flavor and taste, can stimulate consumer demand for aquatic products. Ready-to-eat and semi-prepared foods hold a significant market share, valued for their crispy texture, attractive appearance, color, and enhanced flavor. Deep-frying is a common food processing technique where food is cooked in hot oil at temperatures exceeding the boiling point of water (Chen et al., 2009). This method aims for rapid food processing to extend shelf life while simultaneously creating unique textural, color, aroma, and flavor attributes. Strategies to minimize oil absorption during deep-frying include coating with hydrocolloids (such as edible coatings and gums) and the utilization of bioactive peptides from plant sources. Chia seeds (Salvia hispanica) are recognized for their nutritional richness, including high protein content (15–23%), antioxidants, dietary fiber, vitamins, and minerals. Notably, their oil is abundant in alpha-linolenic acid (Omega-3). Their unique rheological properties and ease of extraction have led to their application as thickening and gelling agents in the food industry, with products formulated using chia seed gum achieving positive consumer acceptance. The text also references Lepidium sativum (garden cress) concerning its oil content and thickening capabilities; however, clarification on the specific scientific name employed in the study may be beneficial. Enzymatic protein hydrolysis, employing either endogenous enzymes (autolysis process) or commercial enzymes, is utilized to improve protein characteristics and enhance bioactivity (Karazhiyan et al., 2009). This study specifically utilized Alcalase (a protease from Bacillus licheniformis with an activity of 4.2 AU/mL) and Flavourzyme (an exopeptidase with an activity of 1.5 AU/mL) (Oveysipour et al., 2012). The primary objective of this research was to assess the antioxidant properties of chia seed protein hydrolysates generated by these enzymes. Furthermore, the study aimed to investigate the impact of a composite coating, comprising alginate and garden cress gum, on the physicochemical and sensory properties of fish nuggets. This research endeavors to leverage these components to enhance the quality and appeal of fish nugget products.
Methodology
Preparation of chia seeds and (Alcalase enzyme - Flowerzyme) extracted from Novazyme, Denmark. The protein content of chia seeds was measured by the Kjeldahl method (Villanueva-Lazo et al., 2022). Preparation of fat-free flour and protein isolate from chia seeds was carried out using the method of Zhou et al. (2006). To measure the hydrolysis of chia seed protein isolate in the present study, 6 treatments were selected. Treatment 1: Flowerzyme + 10 minutes of hydrolysis time. Treatment 2: Flowerzyme + 20 minutes of hydrolysis time. Treatment 3: Flowerzyme + 30 minutes of hydrolysis time. Treatment 4: Alcalase + 10 minutes of hydrolysis time. Treatment 5: Alcalase + 20 minutes of hydrolysis time. Treatment 6: Alcalase + 30 minutes of hydrolysis time. The degree of hydrolysis was calculated using the method of (Villanueva-Lazo et al., 2022). The approximate length of the peptides resulting from hydrolysis was measured (Chatterjee et al., 2015). The protein recovery rate was determined by the Biuret method and the antioxidant activity was determined by the DPPH method (He et al., 2013). Extraction of (Lepidium sativum) seed gum was performed using the method of Karazhiyan et al. (2011). Preparation of wheat flour coating with different percentages by the method (Chen et al., 2009). Fish nuggets (Hypophthalmichthys molitrix) were prepared and physical, chemical, textural and sensory tests were performed (Asadi Farsani, 2018). The moisture content and the amount of absorbed oil were measured using the method (Avak and Glaser, 2005). The texture measurement test was calculated using the Instron texture measurement device according to the method of (Das et al., 2008). The coating percentage and frying efficiency of fish nuggets were calculated according to the formula (Darai Garmkhanei et al., 2009). Peroxide value was measured using the method of (Ronald and Ronald, 1991). (TBA) was measured using a colorimetric method (Hedayatifard and Miri, 2017). The (TVB-N) index was determined by the Kjeldahl method (Avak and Glaser, 2005). Sensory evaluation was investigated using the hedonic test method (Asadi Farsani, 2018).
Results
The initial protein measurements of chia seeds and its protein isolate were (23.91±1.00) and (40.82±1.24), respectively. The results showed that the degree of hydrolysis of the alkalase enzyme was higher than that of flowerzyme (p<0.05). The measurement of protein recovery values showed that the alkalase enzyme was higher than that of flowerzyme (p<0.05). The results of determining the peptide chain length by alkalase were lower than that of flowerzyme (p<0.05). The results of determining the protein levels in different treatments showed that the alkalase enzyme was higher than that of flowerzyme (p<0.05). The results of the DPPH free radical scavenging activity in different treatments showed that the highest activity was related to the alkalase enzyme (82.02%). The results showed that the lowest oil absorption rate was observed in the alginate + gum + 1% hydrolyzed protein (12.15%) treatment (p<0.05). The highest moisture absorption was observed in the treatments of alginate + gum + hydrolyzed protein 0.5 and 1% (56.84 and 57.45 percent, respectively) (p<0.05). The lowest tissue stiffness was observed in the treatment of alginate + gum + 1% hydrolyzed protein (41.7%) (p<0.05). The highest coverage was observed in the treatments of alginate + gum + hydrolyzed protein 0.5 and 1% (36.05 and 36.54%, respectively) (p<0.05). The highest frying efficiency values were observed in the treatments of alginate + gum + hydrolyzed protein with concentrations of 0.5 and 1% (78.93 and 79.24 percent, respectively) (p<0.05). The results of peroxide value under the influence of time and treatment showed that the highest values were observed in the control treatment and the lowest values were observed in the alginate + gum + 1% hydrolyzed protein treatment (p<0.05). The results of statistical analysis of thiobarbituric acid values during the storage period showed that the highest values were observed in the control treatment and the lowest values were observed in the alginate + gum + 1% hydrolyzed protein treatment (p<0.05). The lowest values of volatile nitrogen bases were observed in the alginate + gum + hydrolyzed protein treatment (0.5 and 1 percent) (p<0.05). The results of sensory evaluations showed that the sensory score of the alginate + gum + hydrolyzed protein treatment was 0.5 and 1 percent lower than the other treatments, respectively (p<0.05). In general, the results showed that the alginate and watercress seed gum coating has antioxidant properties and hydrolyzed chia seed protein increased its antioxidant properties, so that the alginate, watercress seed gum and hydrolyzed protein coating significantly delayed the oxidative spoilage process in the nugget and increased the shelf life of the nugget, and in all tests it had a better effect than the synthetic BHA preservative. Therefore, the combination of alginate (2%), watercress seed gum (1%) and hydrolyzed chia seed protein at the level (1% hydrolyzed) with the alcalase enzyme for (30 minutes) can play a significant role in improving the quality characteristics of fried nuggets and increasing their shelf life during storage, and also meet the consumer need for better and safer seafood products.
Conclusions
The protein recovery rate is affected by the increase in the degree of hydrolysis (Ovisipour et al., 2013). The reduction in the peptide chain length of the alcalase enzyme is inversely proportional to the degree of hydrolysis (Namati et al., 2012). DPPH is related to factors such as process time, degree of hydrolysis, and the performance of each enzyme in producing active peptides and releasing lipophilic antioxidant amino acids (He et al., 2013). The reason for the reduction in oil absorption in the treatment is strongly influenced by the solubility and hydrophobicity of the protein surface (Mazloumi-Kiapi et al., 2019). The decrease and increase in moisture in the treatments is due to the gel formation characteristic during heating and the high degree of coating and the creation of a relatively thick layer (Bahrami and Khadami, 2020). Hydrocolloids with their water retention capacity soften the texture of the nugget and reduce the stiffness of the texture (Altunakar et al., 2006). The high coating rate in the two treatments of 0.5 and 1% is due to the amount of adhesive that adheres to the fish nuggets (DaraiGarmkhanei et al., 2014). The frying process causes cell collapse, less oil absorption and increases frying efficiency. (Mokhtariyan and Tavakolipour, 2014). The amount of thiobarbituric acid, due to the coating formed on the surface of the nugget, reduces the amount of product contact with oxygen, the rate of initial oxidation of fats and the subsequent formation of hydroperoxides (Mohan et al., 2007). The amount of nitrogenous bases, by adding a coating, delays the presence of bacteria and the process of autolysis and protein decomposition (Darocha et al., 2018). The overall acceptance index in the 0.5 and 1% treatments was approved by the evaluator (Bahrami and Khademi, 2020 In conclusion, the present study suggests several promising avenues for future research. These include exploring the functional and antioxidant properties of hydrolyzed chia seed proteins through enzymatic hydrolysis using proteases such as bromelain and ficin. Additionally, it is proposed to assess the potential of hydrolyzed chia seed proteins as a sustainable nitrogen source in bacterial culture media, with implications for both food science and biotechnology. Furthermore, investigating the synergistic effect of hydrolyzed chia seed proteins and vacuum packaging could offer a novel approach to enhancing the shelf life of marine products, thereby contributing to more effective food preservation techniques.
Conflict of Interest
The authors declare that they have no conflict of interest
Acknowledgment
The authors would like to express their sincere gratitude to the esteemed Professor Dr. Hedayati Far for his valuable guidance throughout all stages of preparing this article, and to the Caspian Sea Ecology Research Institute for providing the necessary facilities and support for conducting this research |
