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

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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.