the School of Engineering, RMIT Univ., City Campus, Melbourne, VIC, 3001, Australia.
the NSW Dept. of Primary Industries, Yanco Agricultural Inst., Yanco, NSW, 2703, Australia.
J Food Sci. 2019 May;84(5):1104-1112. doi: 10.1111/1750-3841.14599. Epub 2019 Apr 17.
Wastage of byproducts such as canola meal is a pressing environmental concern, and canola protein isolate (CPI)-chitosan (Ch) coacervates have a good potential to utilize and convert the wastes into a high value added product. Yet so far, there is very limited rheological and microstructural information to assist in proper utilization of CPI -Ch complex coacervates. The rheological and microstructural properties of the complex coacervates formed from CPI and chitosan Ch at various CPI-to-Ch mixing ratios (1:1, 16:1, 20:1, and 30:1) and pH values (5.0, 6.0, and 7.0) were therefore investigated. These CPI-Ch complex coacervate phases were found to exhibit elastic behavior as evidenced by significantly higher elastic modulus (G') compared to viscous modulus (G″) in all the tested ratios and pH ranges. They also exhibited shear-thinning behavior during viscous flow. The complex coacervates formed at the optimum CPI-to-Ch ratio of 16:1 and pH of 6.0 demonstrated the highest G', G″, and shear viscosity, which correlated well with the high strength of electrostatic interaction and thick-walled, sponge-like, less-porous microstructure at this condition. The higher shear viscosity of the coacervate at pH 6.0 was most likely induced by stronger attractive electrostatic interactions between CPI and Ch molecules, due to the formation of a rather densely packed complex coacervate structure. Hence, it can be concluded that the microstructural observations of denser structure correlated well with the rheological findings of stronger intermolecular bonds at the optimum CPI-to-Ch ratio of 16:1 and pH of 6.0. The complex coacervate phase formed at a CPI-to-Ch ratio of 16:1 and pH of 6.0 also showed glassy consistency at low temperatures and rubbery consistency above its glass-transition temperature. This study identified the potential for the newly developed CPI-Ch complex coacervate to be used as an encapsulating material due to its favorable strength. This would drastically reduce the wastage of byproducts, provide a solution to tackle the pressing global issue of wastage of byproducts, and bring about a more environmentally friendly paradigm.
菜粕等副产物的浪费是一个紧迫的环境问题，菜粕蛋白分离物（CPI）-壳聚糖（Ch）共沉淀物具有很好的利用和转化废物为高附加值产品的潜力。然而，到目前为止，关于 CPI-Ch 复合凝聚物的流变学和微观结构信息非常有限，难以正确利用 CPI-Ch 复合凝聚物。因此，研究了不同 CPI-壳聚糖混合比（1:1、16:1、20:1 和 30:1）和 pH 值（5.0、6.0 和 7.0）下由 CPI 和壳聚糖 Ch 形成的复合凝聚物的流变性和微观结构特性。结果表明，这些 CPI-Ch 复合凝聚相表现出弹性行为，与所有测试比例和 pH 范围内的粘性模量（G″）相比，弹性模量（G'）明显更高。在粘性流动过程中，它们还表现出剪切变稀行为。在最佳 CPI-壳聚糖比为 16:1 和 pH 值为 6.0 下形成的复合凝聚物表现出最高的 G'、G″和剪切粘度，这与该条件下静电相互作用强度高、壁厚、海绵状、较少多孔的微观结构有关。在 pH 6.0 下，凝聚物的较高剪切粘度很可能是由于 CPI 和 Ch 分子之间形成了更紧密堆积的复合凝聚物结构，从而导致静电相互作用更强。因此，可以得出结论，微观结构观察到的更密集的结构与在最佳 CPI-壳聚糖比为 16:1 和 pH 值为 6.0 时发现的更强分子间键的流变学结果密切相关。在 CPI-壳聚糖比为 16:1 和 pH 值为 6.0 下形成的复合凝聚相在低温下表现出玻璃态一致性，在玻璃化转变温度以上表现出橡胶态一致性。本研究确定了新型 CPI-Ch 复合凝聚物作为包封材料的潜力，因为它具有良好的强度。这将极大地减少副产物的浪费，为解决全球副产物浪费的紧迫问题提供解决方案，并带来更环保的范例。
