@phdthesis{oai:tsukuba.repo.nii.ac.jp:00008568,
 author = {Cheng, Yongqiang and 程, 永強},
 month = {},
 note = {Nowadays, in China, the problem of protein inadequacy still exists. To solve this problem,
low cost, good quality vegetable proteins are considered to be one of the best choices. Among
them, as a good vegetable protein resource, soybean has aroused the attention of many
researchers. Tofu, a kind of soybean product, was invented in ancient time in China and
nowadays, it is still a popular daily dish in some Asian countries like China, Japan, Korea, etc
and is considered as a good vegetable protein resource. For the traditional food culture and the
style of Chinese dishes, Chinese prefer hard tofu. At present, the production of tofu is mainly
done by small-scale factories with handmade way. Such kind of factories can produce hard
tofu meeting the palatability of Chinese consumers. But, the shelf life of tofu is very short, in
summer, only half a day, which limits the distribution of tofu. At the same time, the labor
density is higher, the quality control of tofu is mainly by experiences and a uniform quality is
difficult to be realized. In 1980s’, some industrial lines were imported. But, such kind of
industrial production line uses glucono-delta-lactone (GDL) as coagulant. Tofu produced by
this way is somewhat acidic, which is not preferred by consumers, and the texture of tofu is
very soft, which is not suitable for most of the Chinese dishes. Lack of information on
producing hard tofu by industrial line limit the industrial production of hard tofu in China.
Based on the present situation of hard tofu production in China, this study takes the
improvement of tofu texture in China as the objective.
To improve the texture of tofu, firstly, a proper evaluation method for the texture of tofu is
necessary. Stress-strain, stress relaxation and creep tests were conducted. Results showed that
parameters from stress relaxation and creep behaviors analyzed by using viscoelastic models
(taking Maxwell model, serialized by a Spring model and Dashpot model, and Vigot model,
paralleled by a Spring model and a Dashpot model as primary models) can reflect both the
viscous and elastic changes of tofu with different coagulants and protein concentrations. It
was suggested that this viscoelastic evaluation method was effective for the texture evaluation
of tofu.
After determining the proper texture evaluation method for tofu, in this study, the effects of
soymilk concentration (protein) concentration, types and concentration of different coagulants
(CaSO4, GDL, MgCl2) on the texture of tofu and the effects of okara addition on the texture of
tofu were investigated. For the improvement of tofu texture in China, from the view of protein
concentration, types and concentration of coagulants, the addition of okara, following
conclusions were drawn:
(1) A higher soymilk concentration (protein concentration) can lead to a harder tofu. The
viscosity of soymilk also increased with increasing the protein concentration. A too high
viscosity might cause the difficulties of pipe transportation. In industrial practice, the
balance between protein concentration and a proper viscosity should be considered.
(2) Different coagulants showed different properties to the tofu production. For CaSO4 and
GDL, increasing the amount of coagulant resulted in a harder tofu. MgCl2 showed a
narrow range of optimal concentrations and too high concentration of MgCl2 caused a
ductile break of tofu. When at the same concentration of protein, GDL and MgCl2 can
induce harder tofu than CaSO4. The reaction of MgCl2 with soy protein is rapider than
that of GDL and CaSO4.
(3) It is possible to add paste-like okara to soymilk for the production of tofu. At a certain
range, the texture of tofu was not significantly affected by the addition of okara. CaSO4
showed different response to the addition of okara comparing with GDL. 15% addition of
okara increased the break stress of CaSO4-coagulated tofu while the addition of okara
decreased the break stress of GDL-tofu.
Based on the results in this study, it can be suggested that for industrial hard tofu
production in China, using properly high concentration of soymilk, mixture of coagulants,
such as CaSO4 with MgCl2, GDL with MgCl2, increasing the concentration of coagulants like
CaSO4 and GDL and adding okara can be reasonable alternatives., 2003, Includes bibliographical references},
 school = {筑波大学, University of Tsukuba},
 title = {Improvement of tofu texture in China},
 year = {2004}
}