Lee Chia C, Mulvaney Steven J
Department of Food Science, Cornell University, Ithaca, New York 14853, USA.
J Agric Food Chem. 2003 Apr 9;51(8):2317-27. doi: 10.1021/jf020719l.
Dynamic viscoelastic properties at 25 degrees C of gluten and glutenin gels were obtained from Canadian common wheats of different strengths. The relaxation spectra showed a maximum intensity at a characteristic relaxation time (tau). The relaxation modulus associated with this maximum was taken as the strength of the glutenin or gluten gel transient network (G(tau)). The ratio of G(tau) for glutenin and gluten gels from the same cultivar ranged from 5.6 for an extra strong cultivar to 51.1 for a soft wheat. This gives indirect evidence that the gliadin fraction weakens the glutenin gel network more in weaker cultivars. In addition, the fact that both glutenin and gluten gels showed extensive stress relaxation coupled with the fact that addition of l-cysteine to a gluten gel eliminated the network structure at 25 degrees C and resulted in a power law stress relaxation spectrum suggests that the transient network in gluten is a reversible network. This power law relaxation pattern was not seen here for an entangled polymer melt (poly(dimethylsiloxane)). It was also found here that the viscosity of the gluten gel (G(tau) x tau) trended best with the tensile stress build-up in a uniaxial tensile test of gluten gels. Together, these results indicate that both network strength and relaxation times should be considered in characterizing the linear viscoelastic properties of hydrated cereal proteins.
从不同强度的加拿大普通小麦中获取了25摄氏度下谷蛋白和麦谷蛋白凝胶的动态粘弹性特性。弛豫谱在特征弛豫时间（τ）处显示出最大强度。与该最大值相关的弛豫模量被视为麦谷蛋白或谷蛋白凝胶瞬态网络的强度（G(τ)）。来自同一品种的麦谷蛋白和谷蛋白凝胶的G(τ)比值范围从超强品种的5.6到软质小麦的51.1。这间接证明了在较弱的品种中，醇溶蛋白部分对麦谷蛋白凝胶网络的削弱作用更大。此外，麦谷蛋白和谷蛋白凝胶都表现出广泛的应力松弛，以及向谷蛋白凝胶中添加L-半胱氨酸会在25摄氏度下消除网络结构并产生幂律应力松弛谱这一事实，表明谷蛋白中的瞬态网络是一个可逆网络。在这里，缠结聚合物熔体（聚二甲基硅氧烷）没有出现这种幂律松弛模式。还发现，在谷蛋白凝胶的单轴拉伸试验中，谷蛋白凝胶的粘度（G(τ)×τ）与拉伸应力的建立趋势最为一致。总之，这些结果表明，在表征水合谷物蛋白的线性粘弹性特性时，应同时考虑网络强度和弛豫时间。
