Gel-forming ability of small scale mud carp (Cirrhiana microlepis) unwashed and washed mince as related to endogenous proteinases and transglutaminase activities

Abstract

Gel-forming ability of small scale mud carp (Cirrhiana microlepis) mince and washed mince was investigated with respect to their proteinase and transglutaminase (TGase) activities. Proteinases in sarcoplasmic fluid showed the optimum activity at 65 °C and pH 9, whereas autolytic activity was maximum at 70 °C and pH 10, indicating the presence of heat-stable alkaline proteinases. When mince was washed with three volumes of water twice, TGase and proteinases were mainly removed in the first washing cycle, resulting in a decreased autolytic activity of washed mince. Breaking force of the single washed mince gels was greater than the twice washed mince and the unwashed mince gels (p<0.05). Pre-incubation of mince pastes at 40 °C for 1 h prior to cooking (90 °C/30 min) increased breaking force of all samples, particularly the single washed mince (p<0.05). This coincided with an increase of higher molecular weight polymers observed on SDS-PAGE. Washing did not completely eliminate proteinases as it was evident by an increased trichloroacetic acid (TCA)-soluble oligopeptides of washed gels pre-incubated at 55 °C. Whiteness values of washed mince gels were greater than that of mince gels.