Martin Anna, Osen Raffael, Karbstein Heike Petra, Emin M Azad
Department of Food Process Development, Fraunhofer Institute for Process Engineering and Packaging IVV, 85354 Freising, Germany.
Singapore Institute of Food and Biotechnology Innovation, Agency for Science, Technology and Research (A*STAR), Singapore 138669, Singapore.
Foods. 2021 Mar 14;10(3):616. doi: 10.3390/foods10030616.
Rapeseed press cake (RPC), an oil pressing side product rich in protein and fiber, can be combined with starch and valorized into directly expanded products using extrusion technology. The mechanism of starch expansion has been studied in detail, but the impact of RPC on expansion behavior is poorly understood. However, it can be linked to rheological and physicochemical properties and is a key product quality parameter. Blends with different amounts of RPC (0, 10, 40 g/100 g) were extruded at different barrel temperatures (100, 120, 140 °C) and moisture contents (24 or 29 g/100 g). The initial, intermediate and final sectional, longitudinal and volumetric expansion indices (SEI, LEI, VEI) were monitored directly, 10 s and 24 h after die exit to measure extrudate growth and shrinkage. The viscous and elastic properties of the extruded blends were investigated in a closed cavity rheometer. Starch and blends with 10 g/100 g RPC achieved a high initial SEI followed by significant short-term shrinkage. Blends containing 40 g/100 g RPC did not show any initial expansion. With increasing RPC content, the intermediate SEI decreased, but all samples reached a similar final SEI due to time-dependent swelling of the RPC blends. With increasing RPC content, the elasticity of the starch-based extruded samples significantly increased. Our study shows that comprehensive control and understanding of expansion mechanisms can be achieved only by investigating all stages of extrudate growth and shrinkage. We also found that the closed cavity rheometer is a powerful tool to correlate the rheological properties and expansion mechanisms of biopolymers.
菜籽饼粕（RPC）是一种富含蛋白质和纤维的榨油副产品，可与淀粉混合，并采用挤压技术转化为直接膨化产品。淀粉膨胀的机制已得到详细研究，但RPC对膨胀行为的影响却知之甚少。然而，它与流变学和物理化学性质相关，是关键的产品质量参数。将不同含量（0、10、40克/100克）的RPC混合物在不同的机筒温度（100、120、140℃）和水分含量（24或29克/100克）下进行挤压。在模头出口后10秒和24小时直接监测初始、中间和最终的截面、纵向和体积膨胀指数（SEI、LEI、VEI），以测量挤出物的生长和收缩情况。在密闭腔流变仪中研究了挤出混合物的粘性和弹性特性。淀粉和含有10克/100克RPC的混合物在初始时具有较高的SEI，随后出现明显的短期收缩。含有40克/100克RPC的混合物在初始时未表现出任何膨胀。随着RPC含量的增加，中间SEI降低，但由于RPC混合物随时间的溶胀，所有样品最终的SEI相似。随着RPC含量的增加，淀粉基挤出样品的弹性显著增加。我们的研究表明，只有通过研究挤出物生长和收缩的所有阶段，才能实现对膨胀机制的全面控制和理解。我们还发现，密闭腔流变仪是关联生物聚合物流变特性和膨胀机制的有力工具。
