A COMPARISON OF PHYSICAL AND RHEOLOGIC PROPERTIES OF ARROWTOOTH FLOUNDER PROTEIN MADE USING THREE DIFFERENT EXTRACTING PROCESSES

Abstract

ABSTRACT Soluble and insoluble fish protein powders were made from arrowtooth flounder (AF) fillets using three methods, which were heating and fractionation, enzymatic hydrolysis and alkali protein extraction. The AF powders were compared, and physical, chemical and rheologic properties were evaluated. The alkali protein extraction soluble (AES) (89.6%) and enzymatic hydrolysis soluble (EHS) (84.8%) powders had higher protein contents than other protein powders (72.6–77.8%). Both heating and fractionation soluble (HFS) and heating and fractionation insoluble powders were whiter than the other protein powders. HFS and EHS had the highest nitrogen solubility values, and EHS had the highest emulsion stability values. Sodium dodecyl sulfate electrophoresis indicated AES and alkali protein extraction insoluble protein powders had more high molecular weight protein bands, while EHS, enzymatic hydrolysis insoluble and HFS protein powders were substantially hydrolyzed and had an abundance of low molecular weight peptides. The flow and viscoelastic properties of the emulsions prepared with soluble AF were investigated using a parallel plate rheometer. The power law model was used to determine the flow behavior index (n) and consistency index (K). The emulsion containing AES had the highest K value (85.3 Pa·s) and the lowest value was for EHS (27.3 Pa·s). Soluble arrowtooth powders exhibited pseudoplastic behavior and viscoelastic characteristics. PRACTICAL APPLICATIONS There is an abundance of arrowtooth flounder (AF); however, its utilization as human food is challenging because of the proteases that reduce texture during cooking. Methods of processing are needed to convert the fish into more marketable forms. One alternative is to produce purified protein powder and high-protein ingredients for human consumption. Fish provide an excellent source of very digestable and high-quality protein. Isolated fish protein powders have desirable functional properties, such as the ability to hold water and fat, and emulsifying capacities. Protein from AF can be converted into a high-value protein powder food ingredient. The application of these ingredients could include incorporation into muscle tissue products by injection, tumbling and coating.