Marbling of vegan steak: shear banded fats under enlongational flow and their tribology

植物性食品的兴起是我们社会中最重要和最具变革性的趋势之一。与动物蛋白相比，种植一定量的植物蛋白需要更少的土地、更少的水、更少的废物和更少的能源，同时满足人们的营养、宗教、哲学和动物福利要求。植物基肉类技术的最新发展水平涉及在150 ℃以上的温度下对植物蛋白-淀粉-油混合物进行高水分挤出，并通过长时间固定的冷染色进行精加工，其中材料在约90 ℃的拉伸流动下定向和凝固（溶胶-凝胶转变）。 然而，剪切带状植物基肉的问题，无论是通过伸长还是剪切流动，都是这样一个事实，即它可能是坚韧的，有弹性的，味道干燥，感官特性与动物肌肉的感官特性不同。 其主要原因是它们缺乏结构异质性，特别是与脂肪分布和结合有关的结构异质性。肌肉组织包含脂肪组织，其提供润滑区域，在切割和咀嚼期间可能发生机械故障。这些滑动区对于创造与肉相关的所需质地至关重要。 此外，脂肪携带的味道，这必须分散在整个组织。 所有多晶食用脂肪在这样的高温下都是液体，并且在挤出机中经历毛细管破裂，并与胶凝蛋白质材料相分离。 在过去的两个NSERC发现资助期间，我们发现，表征和设计了可食用脂肪的纳米级结构，并建立了可食用油凝胶领域。我们还发现并表征了纤维素聚合物油凝胶剂乙基纤维素。 乙基纤维素油凝胶在150 ℃和90- 100 ℃左右稳定，使其成为挤出过程中在材料中引入剪切带脂肪的绝佳选择，有效地创造肉类“大理石花纹”。在这里，我们提出的特征延伸流动和摩擦学行为的脂肪和油凝胶系统与长期的相关性。需要对油凝胶和自组装脂质进行摩擦学、毛细管破裂流变学和拉伸流动流变学，所述油凝胶和自组装脂质不仅包括乙基纤维素聚合物油凝胶，还包括卵磷脂-油和偏甘油酯-油混合物。将探索不同分子量的乙基纤维素与不同增塑剂、不同化学组成的卵磷脂和单甘油酯以及不同比例的油类型。所观察到的流变学和摩擦学行为的结构基础将建立使用超小角X射线散射和计算机显微断层扫描。拉曼共聚焦显微镜也将被用于成像不同系统的中尺度，以确认在植物基肉材料内剪切带脂肪的产生。所创造的科学和技术可以被植物性肉类产品的制造商无缝地使用，并有助于在加拿大建立一个重要的新产业。

The rise of plant-based foods is one of the most significant and transformative trends in our society. Less land, less water, less waste and less energy are required to grow a fixed amount of plant protein than animal protein, while fulfilling people's nutritional, religious, philosophical and animal welfare requirements. The state of the art of plant-based meat technology involves high moisture extrusion of plant protein-starch-oil mixtures at temperatures above 150oC, and finished through a long stationary cold dye, where the material orients and sets (sol-gel transition) under enlongational flow at ~90oC.  However, the issue with shear banded plant-based meat, both by enlongation or shear flows, is the fact that it can be tough, elastic and taste dry, with sensory properties that do not resemble those of animal muscle.  The main reason for this is their lack of structural heterogeneity, in particular related to fat distribution and binding. Muscle tissue contains adipose tissue, which provides lubricated regions where mechanical failure can take place during cutting and chewing. These slip zones are critical to creating the required texture associated with meat.  Moreover, fat carries flavor and this must be dispersed throughout the tissue.  All polycrystalline edible fat at such high temperatures are liquid and will undergo capillary breakage in the extruder and phase separate from the gelling proteinaceous material.  During the past two NSERC Discovery funding periods, we have discovered, characterized and engineered the nanoscale structure of edible fats, and established the field of edible oleogels. We also discovered and characterized the cellulosic polymer oleogelator, ethylcellulose.  Ethycellulose oleogels are stable at 150oC and set around 90-100oC, making them an excellent choice to introduce shear banded fat in the material during extrusion, effectively creating meat "marbling". Here we propose to characterize the enlongational flow and tribological behavior of fat and oleogel systems with long correlations. Tribology, capillary breakup rheology, and extensional flow rheology need to be carried out on oleogels and self-assembled lipids, including not only ethylcellulose polymer oleogels, but also lecithin-oil and partial glyceride-oil mixtures. Ethylcellulose of different molecular weights with different plasticizers, lecithin and monoglycerides of different chemical compositions, and oil types at different ratios will be explored. The structural basis for the observed rheological and tribological behavior will be established using ultra small angle x-ray scattering and computed micro-tomography. Raman confocal microscopy will also be utilized to image the mesoscale of the different systems to confirm the creation of shear banded fat within the plant based meat material. The science and technology created could be seamlessly used by manufacturers of plant-based meat products, and help establish a significant new industry in Canada.