30E-9 |
Application of the vane method in textural characterization of soy-based yogurt |
I. V. KOVALENKO, Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA 50011 and J. L. Briggs. The vane method is an emerging large deformation technique in texture characterization of foods, which may be used as an alternative to uniaxial compression tests. Using this rheological method, yield stress and yield strain of various viscoelastic materials may be measured. The objective of the present study was to analyze the applicability of the vane method to detect textural differences between soy yogurts prepared from different soybean varieties at varying protein concentrations. Yield stress and yield strain of soy-based yogurts from five soybean varieties (Vinton 81, Asgrow 2401, HP204, IA2056, IA2025) at Brix values of 6, 8, 10 degrees were evaluated and compared. In addition, the relationship between water-holding capacity and yield stress was investigated. Yield stress values ranging from 133 to 420 Pa at 2.5% protein and 498 to 1171 Pa at 4% protein were dependent on soybean variety and increased with increasing protein concentration. Average yield strain of samples was not affected by protein or variety. Compared to commercial dairy yogurt, the yield stress of soy yogurt was 132 to 445% larger at similar protein content, and was less elastic based on yield strain measurements. Water-holding capacity of soy yogurts was variety dependent, although this dependence was less pronounced at higher protein concentrations. The results showed that the vane method may be effectively used as a rapid and inexpensive technique for detecting textural differences of soy-based yogurts.
Session 30E, Food Engineering: Rheology and texture
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