A mini-process is described for making tofu from 50-g quantities of soybeans. It was used to compare yield and quality among 5 Minnesota grown varieties (Vinton, Corsoy, Hardin, Stine 2510, Stine 2810) and to determine optimum concentration of the coagulant, CaS04. Product yield (wet basis), solids recovery, protein recovery and textural aualitv (Texture Profile Analvsis hardness and fracturabilitv) were optimal at-O:02 N CaS04 for afi 5 varieties. Negative correlations were found between CaSO., concentration and both yield (r = -0.90 to 1.00) and protein recovery (r = -0.96 to 1.00) for all varieties.

This paper proposes an improved active frequency drift (AFD) islanding detection method of a three-phase inverter. Different than the existing single-phase AFD method, in the three-phase system, the disturbance is added to the phase angle, which takes part in coordinate transformation calculations. Thus, the frequency drift of the three-phase reference current can be realized by the disturbance of the phase angle. It is unnecessary to add frequency drift to each phase respectively with the proposed method, which can simplify the control system. Furthermore, the non-detection zone can be eliminated by updating certain parameters; therefore, the detection method is sensitive. In this paper, the application of the proposed method in a digital control system is discussed in detail. The non-detection zone is analyzed, and an elimination method is proposed. Finally, the simulation and experimental results are given to verify the theoretical analysis.

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