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意义的趋势之一。与动物蛋白相比，种植固定数量的植物蛋白需要更少的土地、更少的水、更少的浪费和更少的能源，同时满足人们的营养、宗教、哲学和动物福利要求。植物性肉类技术的最新技术包括在150摄氏度以上的温度下对植物蛋白质-淀粉-油混合物进行高水分挤压，并通过长期静止的冷染料完成加工，在~90摄氏度的长期流动下，材料定向并凝固(溶胶-凝胶转变)。然而，剪切带植物基肉的问题是，无论是延长还是剪切流动，它都可能是坚韧、有弹性和口感干燥的，具有与动物肌肉不同的感官特性。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异质性。肌肉组织含有脂肪组织，脂肪组织提供了在切割和咀嚼过程中可能发生机械故障的润滑区。这些滑动区对于创造与肉类相关的所需质地至关重要。此外，脂肪带有味道，这必须分散在整个组织中。所有多晶食用脂肪在这样的高温下都是液体，会在挤出机中发生毛细血管断裂，并与胶状蛋白质物质分离。在过去的两个NSERC发现资金时期，我们已经发现、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摄氏度下稳定，并在90-100摄氏度左右凝固，使其成为挤压过程中在材料中引入剪切带脂肪的绝佳选择，有效地创造出肉类的“大理石纹”。在这里，我们建议描述具有长相关性的脂肪和油凝胶体系的纵向流动和摩擦学行为。需要对油凝胶和自组装脂类进行摩擦学、毛细管破裂流变学和拉伸流动流变学，不仅包括乙基纤维素聚合物油凝胶，而且还包括卵磷脂-油和部分甘油酯-油混合物。不同分子质量的乙基纤维素与不同的增塑剂，不同化学成分的卵磷脂和单甘酯，以及不同比例的油类型将被探索。利用超小角度x射线散射和计算机显微断层扫描将为观察到的流变学和摩擦学行为建立结构基础。拉曼共聚焦显微镜也将被用来对不同系统的中尺度成像，以确认植物基肉类材料中剪切带脂肪的产生。创造的科学和技术可以被植物性肉类产品制造商无缝使用，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.