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H. G. KRISTINSSON, Dept. of Food Science & Human Nutrition, Univ. of Florida, 130-B Aquatic Foods Pilot Plant, PO Box 110370, Gainesville, FL 32611-0370 Many species of warm and temperate waters are underutilized in the sense that they or their byproducts are not used for human food consumption. The potential exists to utilize these sources for their proteins and lipids. Studies in the author’s laboratory have been conducted to compare acid and alkaline-aided processing with conventional surimi processing to produce protein ingredients from several different warm and temperate water species. The viscosity and solubility profile of the fish proteins have been characterized, and protein recoveries and reduction in lipid content assessed. The color and oxidative quality of the protein ingredients have been investigated, as well as their functional properties, such as gelling ability. Changes occurring in the fish proteins have been investigated on the molecular level to aid in the understanding of changes in function. The highest protein solubility and lowest viscosity was obtained below pH 3 and above pH 10.5 for all species. The acid and alkali-aided processes gave significantly greater protein recoveries and lipid reduction compared to surimi processing. The acid protein isolates (PI) were however highly susceptible to lipid oxidation compared to the alkali PI and surimi, due to more retention of denatured heme proteins. The alkali PI had good oxidative stability compared to surimi. The alkali PI had overall better color characteristics than both acid PI and surimi. The alkali PI produced very strong gels for all species, stronger than surimi, while acid PI resulted in poor gels for most species. These differences could be explained in part by a different effect on protein structure at acid vs. alkaline pH. Results show that alkali-aided processing may be a more successful means of producing functional protein ingredients compared to conventional surimi processing for the species tested. The acid-aided process resulted in quality and functional problems not desirable for fish protein ingredients.
Session 3, Fish protein recovery using pH shifts
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