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Summary: In this study, a film was developed for packaging fish that not only enhanced its shelf life but also was visually receptive to its spoilage. Rose petal extract (RPE) having excellent bioactivity was used as the functional component in carboxymethyl cellulose‐poly vinyl alcohol packaging film. Due to its high anthocyanin content, RPE could be used as a pH indicator, as its colour changed from bright red (pH 2) to yellow (pH 10). The developed film was used for packing Indian Mackerel and assessing its quality during chilled storage. Mackerel packed in neat film spoiled in 3 days while that in RPE containing films had shelf life of 12 days. Total bacterial count, pH, total volatile basic nitrogen and thiobarbituric acid reactive substance of fish in control were higher as compared to in RPE films. On spoilage RPE containing films showed visible colour response from red to green. [ABSTRACT FROM AUTHOR]

Effects of serine protease inhibitor from squid ovary (SOSPI) and egg white powder (EWP) on gel properties of surimi from Indian mackerel ( Rastrelliger kanagurta) were investigated. Breaking force of gel increased when SOSPI levels increased up to 2%. However, EWP showed higher efficiency in increasing breaking force of resulting surimi gel. Nevertheless, SOSPI (0.5-3%) had no effect on deformation. Trichloroacetic acid-soluble peptide content in surimi gel decreased when the levels of SOSPI and EWP increased ( p < .05). This was coincidental with more retained myosin heavy chain. Water holding capacity was increased with the addition of these protein additives, but resulted in lower whiteness. Microstructure study revealed that surimi gel added with 2% EWP was denser and had higher connectivity as compared to that containing 2% SOSPI. The SOSPI had no negative effect on sensory attributes and could serve as the alternative protein additive to improve gel strength of surimi. Practical applications Surimi from dark-fleshed fish is prone to degradation of myofibrillar proteins caused by the endogenous proteases, thereby lowering textural property. To tackle the problem, protease inhibitors (egg white, porcine plasma protein, and bovine plasma protein) have been used by the surimi industries. Due to drawbacks of some particular inhibitors (religious constraints, off-white color, off odor, etc.), the novel additives are still in demand. Ovary from squid processing industry, commonly discarded as the waste, can be an alternative natural protease inhibitor, which can improve the gel properties of surimi, especially produced from dark-fleshed fish. [ABSTRACT FROM AUTHOR]

BACKGROUND Fish proteases, especially trypsin, could be used to prepare fish protein hydrolysates with antioxidative activities. In this study, trypsin from the pyloric caeca of unicorn leatherjacket was purified by ammonium sulfate precipitation and soybean trypsin inhibitor ( SBTI)-Sepharose 4B affinity chromatography. Hydrolysate from Indian mackerel protein isolate with different degrees of hydrolysis (20, 30 and 40% DH) was prepared using the purified trypsin, and antioxidative activities (1,1-diphenyl-2-picrylhydrazyl and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical-scavenging activities, ferric-reducing antioxidant power and ferrous-chelating activity) of the hydrolysate were determined. RESULTS Trypsin was purified 26.43-fold with a yield of 13.43%. The purified trypsin had a molecular weight ( MW) of 23.5 kDa and optimal activity at pH 8.0 and 55 °C. It displayed high stability in the pH range of 6.0-11.0 and was thermally stable up to 50 °C. Both SBTI (0.05 mmol L−1) and N-p-tosyl- l-lysine-chloromethylketone (5 mmol L−1) completely inhibited trypsin activity. Antioxidative activities of the hydrolysate from Indian mackerel protein isolate increased with increasing DH up to 40% ( P < 0.05). Based on sodium dodecyl sulfate polyacrylamide gel electrophoresis, the hydrolysate with 40% DH had a MW lower than 6.5 kDa. CONCLUSION The purified protease from unicorn leatherjacket pyloric caeca was identified as trypsin based on its ability to hydrolyze a specific synthetic substrate and the response to specific trypsin inhibitors. The purified trypsin could hydrolyze Indian mackerel protein isolate, and the resulting hydrolysate exhibited antioxidative activity depending on its DH. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Fish viscera, a waste of fish processing industry, can be exploited as a source of PUFA-rich fish oil for use in food or pharmaceutical industry and at the same time the environment can be protected from pollution by fish wastes. Fish oil was recovered from viscera of Indian Mackerel ( Rastrelliger kanagurta), by different supercritical fluid extraction (SFE) e.g. continuous, co-solvent, soaking, and pressure swing techniques and the yields were compared with that of the solvent extraction method. The SFE parameters such as pressure, temperature, and CO2 flow rate were optimised by employing Response Surface Methodology (RSM) with a view to maximize the oil yield and minimize CO2 consumption. The central composite rotatable design (CCRD) consisting of three variables provided 20 experimental settings. Multiple regressions determined the coefficients of the second-order polynomial equation. The optimum parameters for all 4 techniques applied were found to be 35 MPa, 60 °C, and 2 mL min−1 with an Oil recovery ranging from 93 to 99%. The study demonstrated a lower CO2 consumption by the soaking and pressure swing techniques at the optimized conditions. Thus, the soaking and pressure swing techniques were most effective for extracting oil from fish viscera. [ABSTRACT FROM AUTHOR]

The present study aims to find the effect of freezing methods on the quality of mackerel ( Rastrelliger kanagurta) in commercial plate and air blast freezers during freezing and subsequent frozen storage (−18 °C). Total time for freezing was significantly different ( P < 0.05) between the plate and air blast freezers (90 and 220 min, respectively). This difference in the freezing time could be attributed to the varied quality of the 2 samples. Upon freezing, the moisture content decreased in air blast frozen samples compared to plate freezer where protein content decreased in both the samples. Upon freezing and during frozen storage, lipid oxidation products (peroxide value, thiobarbutiric acid value, and free fatty acid value) and volatile bases (total volatile base nitrogen and trimethyl amine nitrogen) showed an increasing trend in both the samples with values slightly higher in air blast frozen samples compared to plate frozen samples. The total plate counts showed a significantly ( P < 0.05) decreasing trend in both the samples. K value did not show any significant ( P < 0.05) difference between the samples where as the histamine formation was significantly ( P < 0.05) increased in air blast frozen samples compared to plate frozen samples. The taste and overall acceptability was significantly different ( P < 0.05) in plate frozen samples compared to air blast frozen samples on 3rd month. Both samples were in acceptable condition up to 3 mo but the plate frozen samples quality was slightly better than the air blast frozen samples. [ABSTRACT FROM AUTHOR]