Fish skins are rich in collagen and can be used to produce food‐grade gelatin. Films cast from fish‐skin gelatins are stable at room temperature and can act as a barrier when applied to foods. Lysozyme is a food‐safe, antimicrobial enzyme that can also produce gels and films. When cold‐water, fish‐skin gelatin is enhanced with lysozyme, the resulting film has antimicrobial properties. The objective of this study was to characterize the effect on strength and barrier properties of lysozyme‐enhanced fish‐skin gelatin gels and films, and evaluate their activity against potential spoilage bacteria. Solutions containing 6.67% fish‐skin gelatin were formulated to contain varying levels of hen‐egg‐white lysozyme. Gels were evaluated for strength, clarity, and viscoelastic properties. Films were evaluated for water activity, water vapor permeability, and antimicrobial barrier capabilities. Fish‐skin gels containing 0.1% and 0.01% lysozyme had pH (4.8) and gelling‐temperatures (2.1 °C) similar to lysozyme‐free fish‐skin gelatin controls. However, gel strength decreased (up to 20%). Turbidities of gels, with or without lysozyme, were comparable at all concentrations. Films cast with gelatin containing lysozyme demonstrated similar water vapor permeabilities and water activities. Lysozyme was still detectable in most fish gelatin films. More antimicrobial activity was retained in films cast with higher lysozyme concentrations and in films where lysozyme was added after the gelatin had been initially heated. These results suggest that fish‐skin gelatin gels and films, when formulated with lysozyme, may provide a unique, functional barrier to increase the shelf life of food products.

Smoking of meats and fish is one of the earliest preservation technologies developed by humans. In this study, the smoking process was evaluated as a method for reducing oxidation of pink salmon (Oncorhynchus gorbuscha) oils and also maintaining the quality of oil in aged fish prior to oil extraction. Salmon heads that were subjected to high temperatures (95 degrees C) during smoking unexpectedly produced oils with fewer products of oxidation than their unprocessed counterparts, as measured by peroxide value (PV), thiobarbituric acid reactive substances (TBARS), and fatty acids (FA). Higher temperatures and longer smoking times resulted in correspondingly lower quantities of oxidative products in the oils. Fatty acid methyl ester (FAME) analysis of smoke-processed oils confirmed that polyunsaturated fatty acids (PUFA) were not being destroyed. Smoke-processing also imparted antioxidant potential to the extracted oils. Even when antioxidants, such as ethoxyquin or butylated hydroxytoluene, were added to raw oils, the smoke-processed oils still maintained lower levels of oxidation after 14 d of storage. However, decreased antioxidant capacity of smoke-processed oils was noted when they were heated above 75 degrees C. Vitamin studies supported the antioxidant results, with smoke-processed oils displaying higher levels of alpha-tocopherol than raw oils. Results suggest that smoking salmon prior to oil extraction can protect valuable PUFA-rich oils from oxidation. Improved preservation methods for marine oils may extend their usefulness when added as a supplement to enhance levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in foods.

There is a growing interest in developing either food or feed ingredients from the large volumes of Pacific Ocean perch (POP) by‐products produced in Alaska. Determining the chemical composition of POP by‐products is fundamental for developing novel ingredients using these materials. The objective of this study was to chemically characterize POP and its by‐products. Triplicate samples of fresh POP whole fish, heads, frames and viscera were obtained from a commercial seafood processor in Alaska, and each replicate sample was individually analyzed for moisture, lipid, protein, ash, amino acid and mineral contents, fatty acid profile, lipid classes, pH, protein solubility, color, volatile amines and sodium dodecyl sulfate polyacrylamide gel electrophoresis of the proteins. The lipid and protein contents of the POP samples were 7.8 and 17.9% for whole fish, 10.5 and 15.2% for frames, 9.3 and 14.9% for heads, and 13.5 and 11.3% for viscera, respectively. Frames, heads and whole fish had ash values of 6.0, 6.7 and 4.3%, respectively. From the amino acid profiles, the values for lysine ranged from a low value of 7.3% for heads to a high value of 8.3% of total amino acids for frames. Methionine values ranged from 3.2 to 3.4% for all tissues. Frames and heads had high values for calcium and phosphorus, while viscera had the highest levels of iron. The analysis of fatty acids indicated high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) with EPA/DHA ratios of approximately 2 for all tissues. Results indicated that the protein fraction of POP by‐products was of high quality, and its lipids were a valuable source of omega‐3 fatty acids. PRACTICAL APPLICATIONS This paper is the first examination of the chemical and nutritional properties of Pacific Ocean Perch (POP). There are fish processors that process substantial volumes of POP; however, the byproduct is seldom further processed into unique products. Processors could segregate POP byproducts and use this material to make products such as oils with a unique fatty acid profile as well as a distinctive color. Likewise single species POP byproduct meals could be produced and possibly fill niche market needs as food and feed ingredients.

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Hydrolysate production is a low-cost method of preservation that could be employed to decrease the amount of fish by-products discarded by Alaska's salmon industry. However, endogenous enzymes within salmon vary with spawning maturity, and must be controlled in the raw material to ensure a consistent hydrolysate. Differences in proteolytic activities were found among tissue groups (fillets, heads, livers and viscera) in male and female adult pink salmon (Oncorhynchus gorbuscha) harvested at three different levels of spawning maturity. Changes in protease levels may have implications for processing hydrolysates when pink salmon of different maturity levels are used. PRACTICAL APPLICATIONSProteases and other enzymes commonly found in raw fish can interfere with production of a consistent hydrolysate. This study demonstrated that endogenous proteases in pink salmon varied among different tissues as the fish moved from ocean to river environments for spawning. Variation in proteolytic activities among fish tissues will have implications for processors who use different maturity levels of pink salmon to produce hydrolysates, since by-products from a roe-stripped carcass will contain different protease levels than by-products taken from ocean-harvested salmon.