Study On Preparing Organic Tofu Using Salt Incorporated With Polysaccharides

Organic tofu attracts more consumers for it is a “green”,“safety” product in the U. S., thelargest organic food market. As the traditional coagulate, MgCl2create a more natural flavorand allows the taste of the soybean to be retained, these qualities make MgCl2one of the mostpopular coagulants, and consumers also prefer MgCl2-coagulated tofu because it does notspoil the soybean oil. However, MgCl2is a quick-acting coagulant, Tofu coagulated byMgCl2has a lower yield, and rapid solidification causes the tofu to become harder andnonuniform. Although the National List of Allowed and Prohibited Substances includesMgCl2(derived from sea water) in the U. S., the use of MgCl2is limited for these abovedisadvantages in the organic market; Polysaccharides play an important role in modifying thetextural properties of protein food systems. The mixture of MgCl2with three differentpolysaccharides (carrageenan, guar gum and gum Arabic) as tofu coagulant agents wereinvestigated using the indexes of yield, texture and sensory evaluation, compared withtraditionally coagulated tofu (MgCl2, gypsum). Our target was to find a novel organiccoagulant; understand the effect of organic coagulant on the coagulating rate; make theshelf-life model of organic tofu.Adding the compatible coagulant (2.93g MgCl2plus0.6g guar gum) caused the yieldincreased from173%to199%, which was close to the yield (211%) of tofu coagulated bygypsum, while the hardness was decreased to505g. The tofu prepared with the compatiblecoagulant had a similar texture profile to tofu made from gypsum, and good sensatoryevaluation as tofu using MgCl2. the compatible coagulant (2.93g MgCl2plus0.6g guar gum)was selected as a novel organic coagulant.The results of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD),scanning electronic microscope (SEM) and the analysis of the change of viscosity in soymilkshowed the coagulation process divided two stages, firstly, the protein molecular aggregatedto the unit of supermolecular structure and then the units formed the network. The organiccoagulant increased the coagulation rate in the first stage; inversely, the coagulation rate wasdecreased in the second stage. The network of tofu was changed and the properties of tofuwere modified. The microbial growth kinetics was described by the modified Gompertz model, theshelf-life of the organic tofu was75.4,49.2,17.4,6.7h in the temperature of4,10,20,30℃respectively. According to the Arrhenius equation: Lnθ=-bT+c, the equation of the shelf-lifeof the organic tofu was described as Lnθ=-0.0948T+4.7576,(R2=0.9971).