Thermogelation properties of methylcellulose (MC) and their effect on a batter formula

摘要

Thermogelation properties of both a solution of methylcellulose (MC) and of a batter formula containing 1, 1.5 and 2% MC were studied by small amplitude oscillatory shear, simulating the thermal process undergone by batters in an innovative process for industrial battered food manufacturing which eliminates the pre-frying step. The mechanical spectra of the MC solution carried out at 15 and 60℃ clearly showed a transition from a fluid-like to a gel-like behaviour. The evolution of G′ and G″ with an upward temperature ramp showed the sol-gel transition to occur at approximately 52℃ (estimated as the crossover between G″ and G′). As the temperature was lowered a complete reversing of the gelation process was observed. Increasing the temperature of MC batters resulted in a transition from a soft gel at 15℃ (behaviour in the innovative process before the coagulation step) to a stronger although still soft gel at 60℃ (behaviour after the coagulation in hot water). At both temperatures G′ and G″ increased with MC concentration, although MC did not seem to qualitatively influence the viscoelastic behaviour. In comparison with the same batter formula without MC, the batters containing MC actually used for the innovative process exhibited a characteristic profile, whose main features were a significant decrease in |G~*| when initially increasing temperature, a decrease in the temperature at which |G~*| starts to increase and a tendency towards a reversing upon cooling.