Emulsifying and gelling properties of weakfish myofibrillar proteins as affected by squid mantle myofibrillar proteins in a model system

Abstract

The aim of the present work was to investigate the physicochemical, biochemical and functional characteristics of both the myofibrils (MF) and actomyosin (AM) of squid mantle (Illex argentinus) and weakfish (Cynoscion guatucupa) muscles, and evaluate the influence of the addition of myofibrilar proteins from the squid mantle on the physicochemical and functional properties of those of the weakfish. After extraction, purification and characterization of the MF and AM of both species, emulsions of each protein fraction from each muscle were formulated. Mixtures of the MF or AM of both species were also analyzed. The emulsifying properties were monitoring using the Emulsifying Activity Index (EAI) and Emulsion Stability (ES). In addition, gel pastes were formulated from the squid mantle, weakfish muscle and the mixture of both species, and the following functional properties of the gels assessed: water holding capacity, colour, textural profile analysis (TPA) (hardness, elasticity, cohesiveness, gumminess) and gel strength. The EAI values of emulsions formulated with the MF of the mantle were significantly (p<0.05) higher than those formulated from those of weakfish. The incorporation of squid MF in the mixture increased the EAI values. Conversely, the highest ES values were obtained with weakfish MF, and the incorporation of MF weakfish in the mixture increased the ES values. Similar EAI and ES behaviours were observed for the AM of the corresponding species. Irrespective of the thermal treatment, the gel strength of the gelled paste of squid muscle was significantly (p<0.05) lower than that of weakfish muscle and of those obtained with the different mixtures. The behaviours of the expressible moisture (EM) from the gelled pastes were similar to those of gel strength. Irrespective of the thermal treatment, the pastes formulated with a high weakfish: mantle ratio showed less water loss. The gelled pastes of squid mantle showed the highest values for whiteness (WI) and the incorporation of squid muscle protein improved the WI of the mixtures.