Functional, thermal, and physicochemical properties of proteins from Argentine croaker (Umbrina canosai) recovered by solubilization/precipitation or a washing process

Proteins were recovered from Argentine croaker by two methods: alkaline extraction-isoelectric precipitation and a washing process with cold distilled water and sodium chloride. The objective of this study was to evaluate the effect of the recovery method on the physicochemical, structural, thermal and functional properties of proteins recovered from the Argentine croaker muscle. The alkaline extraction-isoelectric precipitation and washing process yielded significantly different (p < 0.05) protein contents of 92.13% (as isolated protein) and 88.70% (as myofibrillar protein), respectively. Polar amino acids comprise approximately 61.50% and 59.80% of the myofibrillar and isolated protein, respectively. The digestibility of the myofibrillar and isolated protein did not differ significantly (p > 0.05). The isolated protein had a lower lightness (81.04) than the myofibrillar protein (83.87) but high redness (2.55) and yellowness (15.47) values. The total enthalpy of denaturation of the myofibrillar protein (1.47 J/g) was higher than that of the isolated protein (0.33 J/g). The myofibrillar protein showed more compact ultrastructures and higher protein degradation than the isolated protein. The solubility and water-holding capacity of the isolated protein were higher than those of the myofibrillar protein at the same pH. Functional studies show that pH-shift processing may improve the functional properties of Argentine croaker proteins relative to myofibrillar protein. However, the results also show that some of the characteristics, as color and thermal properties, of the isolated protein were lower than those of the myofibrillar protein, suggesting that the two materials can be used to obtain different products with high added value. (c) All Rights Reserved