Studies on the Process of Produced and Quality of Tofu Part I. Physical Properties of Tofu Produced Using Citrus Fresh Fruit Juice and Ume-zu as Coagulation Agent.

Abstract

Fresh fruit juice including Sudachi, Yuzu, lemon and Kabosu and Ume-zu containing organic acids and Nigari components were using by applying the acid coagulation properties of soybean protein to examine their availability as a coagulation agent in the production of tofu. Tofu products being marketed using a chemically synthesized coagulation agent (calcium sulfate) were also tested as a control. The physical properties of the control products and test products were compared and examined. Production was carried out according to a common method employing automated production on a large-scale. Each fresh fruit juice was added at an amount of from 1.0-3.0% based on the weight of the soybean milk. In the 1.0-2.0% lots, the physical properties of the tofu products were somewhat insufficient, but the 3.0% lot showed good physical properties. The coagulation effects (rates) of the soybean milk prepared using fresh fruit juice as a coagulation agent were elevated with an increase in the addition ratio. They depended on the pH values of the fresh fruit juice per se. Namely, the coagulation effects were elevated under strongly acidic condition and the strongly acidic Ume-zu containing Nigari components showed further enhanced coagulation effects. When the coagulation effects were increased, the physical properties (hardness, penetration, elasticity and sectility) were increased and the products thus obtained scarcely differed from the marketed and control ones. In total, soft tofu products were obtained in these cases. The 3.0% fresh fruit juice lots showed the best results. In particular, excellent tofu products could be obtained in the Ume-zu and Yuzu lots, followed by the Sudachi, Kabosu and lemon lots. These results agreed with the strongly acidic pH values of the fresh fruit juice per se. The surface color tones of tested tofu samples differed greatly from those of the marketed products and the control products in numerical value. However, little difference was observed with the naked eye. Based on the these results, it is concluded that fresh citrus fruit juice are sufficiently applicable to the production of common tofu products from the viewpoint of physical properties.