| Soymilk is a traditional, high-quality and low-cost protein resource, however, because of the strong beany flavor, the market acceptance has been at a low level. During the processing and storage period, soymilk is prone to have quality problems such as protein precipitation, fat floating and so on. This research developed a kind of nutritious and delicious juice soymilk beverage by combining soymilk with juice perfectly, and its storage stability was studied.The effects of heat treatment of soybean and the pretreatment of soymilk on quality were investigated. The results showed that a kind of soymilk with little beany flavor was available under the conditions of baking at 150℃for 2 min, grinding at the temperature higher than 60℃, and cooking at 95℃for 15min; through the process of centrifugation at 3000r/min for 10min, the insoluble solids content of soymilk decreased effectively, the sedimentation fell to 1.25% and the volume weighted average particle size (D[4,3]) was 5.80μm.The effects of the stabilizer, emulsifier, chelator, fruit juice, and the process of acidification, homogenization and pasteurization on the stability and the taste of juice soymilk beverage were studied. According to orthogonal designs, quadratic regression orthogonal design and response surface analysis methods, the obtained optimized juice soymilk beverage formula was as followed:0.5%single stabilizer 2 CMC,0.05% compound emulsifier,0.09%compound chelator, and 10%peach juice. The obtained optimized process parameters were adjusting pH to 4.2 at 20℃, homogenizing at 20-25MPa, and pasteurizing at 85℃for 15min.According to zeta-potential, the soy protein's isoelectric point was 4.50. In the acidizing process, there was a great change of zeta-potential and particle size distribution of CMC-soy protein system:when pH decreased from 7.0 to 3.5, the zeta-potential (all of them were negative, and the absolute value was larger than 20mv) increased at first and then decreased, reached the maximum value of -57.5mv at pH5.5, and fell to-26.0 mv at pH3.5. As pH decreasing, D[4,3] decreased at first and then increased, fell to the minimum value of 5.827μm at pH4.0. At pH3.5, D[4,3] increased, so the stability decreased.The effects of the homogenization on stability of juice soymilk beverage were studied with the addition of 0-1.0% CMC. The results showed that the sedimentation of fruit juice soymilk with the addition of 0.2% CMC was still up to 16.98% after homogenization, which means homogenization couldn't change the originally unstable system; with the addition of 0.4%CMC, the product's stability significantly increased after homogenization:the curve of particle size distribution presented a double-peak, a distribution area of small particles with ranging from 0.04μm to 1μm appeared, D[4,3] decreased, and the sedimentation reduced from 7.75% to 1.72%; When the addition of CMC is up to 1.0%, the distribution area of small particles disappeared, the sedimentation increased, and the product's stability decreased.After storage at 37℃for 56 days, the juice soymilk beverage presented a good physical stability, had a slight degree of delamination, and fat floating. Particle size distribution, viscosity, centrifugal sedimentation didn't change significantly, about 94% of particles were less than 10μm, the viscosity ranged from 5.8cP to 6.6cP, and the sedimentation was less than 1.31%. |
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