30A-11 |
The effect of soy oil and lecithin on the texture of curds prepared from chickpeas, lentils and smooth peas |
R. CAI and B. K. BAIK. Department of Food Science & Human Nutrition and IMPACT, Washington State University, Pullman, WA 99164-6376 Bean curds prepared from chickpeas, lentils and smooth peas had less favorable texture than soy tofu. The differences in lipid content of soybeans and other legumes may be among the factors causing the variations in curd property. Therefore, an investigation on the role of lipids in curd formation is necessary. Our objective was to determine the effect of soy oil and lecithin on the texture of bean curds prepared from chickpeas, lentils and smooth peas. Bean curds were prepared from legume proteins by heat- and coagulant-induced gelation with and without the addition of soy oil or lecithin. Textures of curds were evaluated using a textural analyzer. The nature of protein-lipid interactions was evaluated using differential scanning calorimetry (DSC), viscometric analysis and surface hydrophobicity. Soybean oil slightly decreased, while the addition of 5-20% lecithin increased the hardness of chickpea curd from 7.8 N to 10.5-13.9 N. Lecithin also increased chickpea curd cohesiveness. Curds of smooth peas and lentils were not affected by the addition of either lipids. Both lipids slightly lowered the denaturation enthalpy of chickpea and lentil proteins. Soy oil slightly increased, while lecithin decreased the viscosity of legume protein solutions. Soy oil had no effect, while lecithin significantly increased the surface hydrophobicity of legume proteins from 23.1 to 31.0, from 26.2 to 36.3 and from 29.6 to 38.2 at pH 6.4 for chickpeas, lentils and smooth peas, respectively. The results suggest that the electrostatic interactions between proteins and lecithin may cause a decrease in viscosity because of the more compact structure of the interacted complex. The decrease in overall negative charges on the protein surface by lecithin may result in an increase in curd hardness. On the other hand, the increase in surface hydrophobicity in the presence of lecithin suggests that binding occurred between protein and lecithin molecules.
Session 30A, Food Chemistry: Lipids
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