COMPARATIVE STUDY OF THE DSC PATTERN, COLOR, TEXTURE AND WATER-BINDING CAPACITY OF RAINBOW TROUT MUSCLE DURING HEATING

Abstract

ABSTRACT The effect of heating the muscle of rainbow trout at different temperatures ranging from 30 to 70C on thermal stability, texture, water-holding ability and color was investigated with regard to the possibility of discriminating between thermally treated and untreated fish muscle. Including the skin of fish it was possible to differentiate heat-treated fish in 5C steps in the range of 35–65C by means of their differential scanning calorimetry (DSC) patterns. Heating the fish muscle resulted in a marked increase in lightness with rising temperature as well as significant changes in hardness (increase) and water-holding capacity (decrease). Heating effects were compared with those of pressure treatments at 100 and 200 MPa for 20 min. The DSC patterns of both trout muscle and skin were comparable for samples that were pressure treated at 200 MPa or heated at 40C. PRACTICAL APPLICATIONS Differential scanning calorimetric (DSC) patterns of both muscle proteins and skin proteins of rainbow trout preheated at temperatures ranging from 30 to 70C show a gradual denaturation of protein fractions, with myosin being the most susceptible and almost completely denatured in samples preheated at 50C. In samples preheated at 70C, the actin peak also disappeared and proteins available in muscle and skin were fully denatured. This offers the possibility of checking whether heat treatment has been performed (e.g., in the case of illegal tariff savings) or whether minimum cooking temperatures have been met (e.g., in the case of hot smoking).