Textural behavior of gels formed by rice starch and whey protein isolate: Concentration and crosshead velocities

ABSTRACT Fabricated food gels involving the use of hydrocolloids are gaining polpularity as confectionery/convenience foods. Starch is commonly combined with a hydrocolloid (protein our polyssacharides), particularly in the food industry, since native starches generally do not have ideal properties for the preparation of food products. Therefore the texture studies of starch-protein mixtures could provide a new approach in producing starch-based food products, being thus acritical attribute that needs to be carefully adjusted to the consumer liking. This work investigated the texture and rheological properties of mixed gels of different concentrations of rice starch (15%, 17.5%, and 20%) and whey protein isolate (0%, 3%, and 6%) with different crosshead velocities (0.05, 5.0, and 10.0 mm/s) using a Box-Behnken experimental design. The samples were submitted to uniaxial compression tests with 80% deformation in order to determinate the following rheological parameters: Young’s modulus, fracture stress, fracture deformation, recoverable energy, and apparent biaxial elongational viscosity. Gels with a higher rice starch concentration that were submitted to higher test velocities were more rigid and resistant, while the whey protein isolate concentration had little influence on these properties. The gels showed a higher recoverable energy when the crosshead velocity was higher, and the apparent biaxial elongational viscosity was also influenced by this factor. Therefore, mixed gels exhibit different properties depending on the rice starch concentration and crosshead velocity.摘要 以亲水胶体（hydrocolloid）制备的人造食品凝胶，作为糖果类/便捷食品正日益受到市场欢迎。淀粉常与亲水胶体（蛋白质或多糖）复配，在食品工业中应用广泛，这是因为天然淀粉通常不具备制备食品所需的理想性能。因此，对淀粉-蛋白质复配体系的质构研究可为淀粉基食品的生产提供新路径，而质构作为需贴合消费者偏好进行精细调控的关键属性，其调控至关重要。本研究采用Box-Behnken实验设计，探究了不同浓度大米淀粉（15%、17.5%、20%）与乳清分离蛋白（whey protein isolate，WPI）（0%、3%、6%）的复配凝胶，在不同十字头速度（0.05、5.0、10.0 mm/s）下的质构与流变学特性。实验对样品施加80%变形量的单轴压缩试验，以测定以下流变学参数：杨氏模量（Young’s modulus）、断裂应力、断裂变形量、可恢复能量以及表观双轴拉伸黏度。结果显示，大米淀粉浓度更高的凝胶，在更高测试速度下会表现出更强的刚性与抗形变能力，而乳清分离蛋白的浓度对这些特性的影响较小；当十字头速度提升时，凝胶的可恢复能量更高，表观双轴拉伸黏度同样受该因素影响。综上，复配凝胶的特性会随大米淀粉浓度与十字头速度的变化而产生差异。