Effect of Pulsed Electric Field-Assisted Process in Combination with Porcine Lipase on Defatting of Seabass Skin.

Defatting of seabass skins using pulsed electric field (PEF)-assisted process at different electric field strengths (16 and 24 kV/cm) and times (36, 72, and 108 ms) in combination with porcine pancreas lipase (PPL) at 25 U/g dry matter was investigated. PEF-treated skin at 24 kV/cm for 72 ms followed by PPL treatment removed 86.93% lipids. PEF-treated skin was further optimized for lipid reduction by response surface methodology. Central composite design was adopted to establish treatments based on two independent variables, involving PPL concentration (30 to 55 U/g dry matter) and hydrolysis time (60 to 180 min). Second-order polynomial model was used for predicting the response. The highest lipid removal (91.96 ± 1.70%) was attained when the optimal condition (42.36 PPL units/g dry skin matter for 139.78 min) was used. The experiment value was in accordance with the predicted value. PEF-PPL-treated skin had lower monounsaturated and polyunsaturated fatty acids than the solvent-extracted skin (P < 0.05). When PEF-PPL-treated skin was hydrolyzed using papain at 0.30 U/g dry matter, lower fishy odor/flavor of resulting hydrolyzed collagen (PEF-PPL-HC) was found than other samples (P < 0.05). Lower total volatile compounds were also obtained in PEF-PPL-HC sample. Thus, the use of PEF pretreatment along with PPL before papain hydrolysis effectively prevented the formation of fishy odor/flavor in hydrolyzed collagen from seabass skin. PRACTICAL APPLICATION: Fishy odor/flavor caused by lipid oxidation of fish skin hydrolysates limits their applications in foods. Defatting process is the significant step for skin pretreatment. Although several methods could remove lipids from fish skins, either by lipase or solvent extraction, fishy odor/flavor is still detected in hydrolysate. Pulsed electric field-assisted process in combination with porcine lipase is another approach that can be used to enhance efficiency via electroporation, causing the loosened skin matrix and facilitating the migration of lipase into the skin. Consequently, the resulting hydrolysate might have the lowered fishy odor/flavor and could be used in foods, especially for fortification.