Production of Water Soluble Antioxidative Plastein from Squid Hepatopancreas

To utilize a typical squid processing by-product, hepatopancreas was enzymatically hydrolyzed, then subjected to a plastein reaction. The substrate concentration that gave the highest plastein yield was 30% by using Alkalase. The optimum pH for the plastein synthesis with Alkalase ranged from 6 to 9. The dominant molecular size of the formed plastein was about 2000. Alkalase mediated plastein reaction seemed beneficial for enriching aspartic acid and glutamic acid, and eliminating hydrophobic amino acids such as phenylalanine, tyrosine, leucine, and isoleucine. Despite the heat pretreatment, hydrolysate powder and plastein retained their antioxidative affect, but a discouraging drawback of the hydrolysate was an unacceptable stimulating taste. For this reason, plastein was considered to be a much better choice to use as an antioxidant because it was tasteless. Plastein from squid hepatopancreas may be a useful antioxidant because it is stable against heat, dissolves easily in water and suppresses the proxidative effect of metals on lipid oxidation.