EXAMINATION OF PLANT PROTEINS AND THEIR BEHAVIOUR DURING TWIN SCREW EXTRUSION

Joshua Bernin

The consumption of plant-based meat analogs has been on the rise in the last decade due to their nutritional value, sustainability, and necessity to meet global protein demands. However, the production of plant-based meat analogs produced using twin-screw extrusion and the main mechanisms of texturization are yet to be fully explored. Therefore, this dissertation attempts to understand the mechanisms of texturization during twin-screw extrusion at both high and low-moisture extrusion. Extrusion is a multiple-input multiple-output system that allows for the continuous production of products. There are two types of meat analogs that are produced using this technique, low-moisture (LMMA) and high-moisture meat analogs (HMMA). Low-moisture meat analogs are typically extruded at moisture contents ranging from 20% to 40%. Low-moisture meat analogs are generally produced utilizing a protein-starch blend and extruded using a venturi before the die nozzle. High-moisture meat analogs are typically extruded at moisture contents ranging from 45% to 80% and extruded using a cooling die. Due to these differences in the production of various meat analogs, it is difficult to fundamentally understand the mechanisms of texturization. Therefore, this dissertation first assessed three different die designs and their effect on the quality of the HMMA. Then, sodium metabisulfite, glutathione, and cysteine were utilized to assess the effect that these reducing agents had on the texture and fiber formation of HMMA. These two ideas were then combined using two different cooling dies and two reducing agents (glutathione and sodium metabisulfite) to analyze how the reducing agents affect the flow of the melt through cooling dies of different sizes. These studies show that during high-moisture extrusion, the rate of cooling, disulfide bond concentration, and protein-water interactions affect the quality of the extrudate. The last part of the dissertation evaluated how starch and extrusion parameters affect the integrity and quality of the extrudate. From these studies, it was observed that increasing energy increased the protein complexation, and starch was mainly utilized as a processing aid, creating the melt in the extruder and helping to support expansion. The findings in this dissertation will improve the knowledge of the mechanisms behind protein texturization and will assist in scale-up and improving the quality of texturized vegetable protein.

EXAMINATION OF PLANT PROTEINS AND THEIR BEHAVIOUR DURING TWIN SCREW EXTRUSION

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