Studies On Concentrated Tofu Preparatin Process And Physical Properties

This article prepared protein gel made from soy protein isolate to determine the protein gel process parameters. And then on the basis of this process, this paper took the soybean as raw material to prepare concentrated tofu and researched coagulant addition concentration; the main ingredient of concentrated tofu was detected and compared with those of commercial tofu; the formation force of tofu gel prepared with bittern was discussed, aiming at revealing the mechanism of protein gel and providing theoretical basis and product data for the product industrialized production.The protein gel was prepared with the soy protein isolate. The results showed that the optimum conditions for preparing gel were 14%(w/v) of soybean protein isolate concentration,0.6%(w/w) of coagulant concentration,90℃ of coagulation temperature and of 30 min coagulation time. The protein concentration of gel was 10.4%, which laid a foundation for the next experiment.The soybeans were took as the raw material to prepare concentrated tofu. The results showed that when soy milk volume was concentrated to 230 ml with 100 g soybeans, the protein concentration of tofu gel was 10.4%. Therefore, the article selected this concentration as the optimal one for preparing concentrated tofu.The best usage of different coagulant was researched. The results showed that bittern optimal usage was 0.5 g/100 mL and the best amount of glucono lactone was 0.25 g/100 mL.And the optimal concentration of composite coagulants was 0.58%, wherein the proportion of glucono lactone and bittern 1:3. Compared with concentrated tofu prepared single coagulant, that of prepared by composite coagulants had better textural properties and organoleptic properties.The spectrum analysis by scanning electron microscopy (SEM) further validated above result.The main ingredient of concentrated tofu is detected and compared with those of commercial tofu. The results showed that all ingredients in concentrated tofu were higher than those in commercial tofu. Therefore, compared to the commercial tofu, concentrated tofu had higher nutritional value.In order to reveal the gel formation mechanism, protein gel intermolecular forces were studied by indirect means, which observed the changes of gel properties after adding reagents that can strengthen or weaken the force between the protein molecules. The study of the impact of changes in the characteristics of the gel texture through different pH and NaCl concentration, the results show that electrostatic interactions play an important role in the formation of gel and electrostatic repulsion between the protein molecules was overcome. The study about impact of disulfidethreitol (DTT) on the gel texture and the changes of sulfhydryl content indicated that the disulfide bonds played an important role in the gel-forming process and could promoted gel-forming. Through the study on that impact of sodium dodecyl sulfate (SDS) on the characteristics of the gel texture and hydrophobicity measured, the results showed that hydrophobic interactions have a significant role on tofu gels.In addition, urea added confirmed hydrogen bonds had an important impact on the gel formation.