Changes in lipids of shrimp (Acetes vulgaris) during salting and fermentation

Abstract

Changes in lipids of shrimp Acetes vulgaris during production of Kapi (salted shrimp paste of Thailand) were investigated. Shrimp had lipid content of 4.21% (dry weight basis). Lipids mainly consisted of triacylglycerol (TAG) (28.03%) and sterol (ST) (24.03%). Lipid content decreased during salting, drying and the first period of fermentation (p < 0.05). Both TAG and ST gradually decreased, while free fatty acid (FFA) increased and became dominant in the final product (49.29%). Phospholipids including phosphatidylethanolamine (PE) (4.80%) and phosphatidylcholine (PC) (5.67%) were also found in fresh shrimp and still remained in the final product. Palmitic acid (C16:0) was the major fatty acid in shrimp (27.95%). Eicosapentaenoic acid (EPA) (C20:5(n-3)) and docosahexaenoic acid (DHA) (C22:6(n-)) were found at high content (19.03%). When different fractions were isolated from crude lipids, varying fatty acid profiles were obtained. TAG and FFA fractions mainly consisted of saturated and monounsaturated fatty acids. Polyunsaturated fatty acids were accumulated in PE and PC fractions. Peroxide value and TBARS value increased during Kapi production, suggesting that lipid oxidation took place. Overall, lipolysis and oxidation of shrimp lipids occurred throughout the processes, thereby affecting lipid constituents. Those changes might partially contribute to the Kapi characteristics, especially flavor.

Practical applications: Kapi, salted shrimp paste, is one of the most popular traditional condiments used in Thailand. Over the last decade, shrimp Acetes vulgaris, by-catch from commercial fishing, has become the alternative raw material for Kapi production instead of krill (Mesopodopsis spp.). During processing, changes in lipids via both lipolysis and lipid oxidation occurred. This work provides the information about lipids from this shrimp species and their changes during Kapi production, which might determine sensory properties, especially odor or flavors, as well as nutritive value of the final product.

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