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Chemical (pH 3.3, 70°C, 85°C; pH 12, 70°C, 85°C) and biochemical (Alcalase, Protamex, Neutrase, Flavourzyme, and Trypsin) hydrolysis of Persian sturgeon (Acipenser persicus) visceral protein was investigated. The results of this study revealed that there are significant differences between enzymes in terms of degree of hydrolysis (DH%; P < 0.05). Alcalase-hydrolyzed fish protein had the highest DH% (50.13%), and Trypsinhydrolyzed fish protein had the minimum DH% (14.21%). The highest DH% in chemical hydrolysis was related to pH 3.3 at 85°C (68.87%). The highest protein recovery (83.64%) and protein content (73.34) were related to enzymatic hydrolysis by Alcalase. The results of current study showed the significant effect of hydrolysis conditions on fish protein hydrolysate properties. Microbial enzymes could produce fish hydrolysates with higher degree of hydrolysis when compared to animal enzyme. Also, in chemical hydrolysis it is clear that hydrolysis at the lower pH and at higher temperature causes to more protein recovery and degree of hydrolysis.

The aim of the present study was to investigate the effect of wall materials composition on physicochemical characteristics of fish oil microcapsule produced by spray-drying (180 oC). Four different combination of coating materials (fish gelatin, chitosan, combination of gelatin and chitosan and a mixture of microbial transglutaminase (MTGase) with maltodextrin) were applied to two different fish oils to produce 40% solid emulsions. Scanning electron microscopy and extraction of surface and encapsulated oils revealed that fish gelatin had the highest ability of covering fish oil ; Meantime, addition of MTGase to gelatin could also increase this ability and reveled less surface oil (2.63% than 5.23% on chitosan treatment (P<0.05). Mixture of gelatin and maltodextrin with MTGase as the wall material led to a high encapsulation efficiency 88%, so was selected as the best microcapsule. However, application of chitosan with maltodextrin had lower encapsulation efficiency ~67% (P<0.05). All indices of powders (encapsulation efficiency, surface morphology and particle size) showed that powders prepared from gelatin and gelatin with MTGase increased efficiency of encapsulation and will increase stability of the microcapsules powders.

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The effect of preliminary ascorbic and citric acid (AA and CA, respectively) soaking treatments on the rancidity development in Wels catfish (Silurus glanis) fillets during further frozen storage ()18°C; up to 6 months) was studied. Rancidity development was measured by biochemical quality indices (formation of free fatty acids, peroxides and secondary oxidation products) and compared with sensory analysis (appearance, rancid odour and consistency) and general chemical analyses (pH, expressible moisture and heme iron contents). When compared with control samples, AA-and CA-treated samples showed a lower (P < 0.05) formation of primary and secondary lipid oxidation compounds that was corroborated by a longer (P < 0.05) shelf-life time as a result of a lower rancid odour formation. According to these results, control samples showed a higher (P < 0.05) heme iron breakdown (months 3-6) and a lower (P < 0.05) water-holding capacity (higher expressible moisture value) (month 6).