Effects of different carrageenan types on the rheological and water holding properties of tofu

Effects of three carrageenan types including kappa/iota-hybrid carrageenan, kappa/iota-mixture carrageenan, and K+-kappa-carrageenan in the concentrations of 0.5 g/kg, 1.5 g/kg, 2.5 g/kg on the texture, rheological property, microstructure, and water holding property of tofu were compared for texture control. Types of carrageenan repeating units affected the coagulation process by changing the protein aggregation behavior in heated soymilk, resulting in the formation of tofu with distinct rheological and water-holding properties. The hardness and elasticity of tofu with kappa/iota-hybrid carrageenan were higher. The addition of carrageenan increased the expressible water of tofu without varying its syneresis. The stress relaxation data suggested two relaxation mechanisms in tofu. One appears at a shorter time between 0.4 and 15 s for both lambda(1) and lambda(2) that represents the aqueous phase with buffering ability in the tofu matrix. The other shows at a longer time around 60-95 s (lambda(3)), that represents the network frame structure in the matrix. The addition of carrageenan increased the lambda(3) of tofu, indicating the decrease of network chain mobility. Tofu became softer and less elastic when the concentration of carrageenan was increased. The above phenomenon might be due to the changes in the network structure of tofu by carrageenan. (C) 2016 Elsevier Ltd. All rights reserved.