The second part focused on understanding the cooling die unit operation from an engineering standpoint, especially with regards to developing a conceptual framework for how such dies could be scaled up and operated. It was found that the product temperature gradient achieved during cooling dictated the HMMA textural and structural quality for a given fixed formulation. As an extension to this, taller dies are associated with better anisotropy characteristics, given the flow characteristics they enable and the slower heat transfer rates achieved through the thicker product cross section. These studies also helped identify slip flow and phase change energy as important new concepts around which further understanding of the HMMA structuring mechanism could be built. Finally, a novel extrusion experiment showed that maintaining the hot temperatures from which melt is discharged from the extruder barrel early in the cooling die can lead to significant improvements in structuring, as doing so favorably lowers the product cooling rate while extending the amount of time that the product has to develop a beneficial laminar flow profile before solidifying.

It is not realistic to expect the current means of animal meat production to sustainably keep pace with increasing populations and appetites for such products. Meat substitutes and analogs made from plant proteins offer one possible avenue to provide essential nutrition to people in a world where real meat will soon be very expensive. Meat substitutes such as tofu or discombobulated meat analogs like texturized vegetable protein have been around for a very long time now, and have well defined markets and culinary uses. Extruded high moisture meat analog (HMMA) is a newer technology that is meant to mimic whole cuts of meat, but is much more expensive to produce since not much public effort has gone into understanding the practical aspects of the process. This dissertation aims to rectify this research gap by holistically understanding the impact that extrusion processing conditions have on protein chemistry during

In the first part of this dissertation, the effects that altering the HMMA formulation and process have on HMMA quality was explored. Formulation was found to be very important, as moisture content, the protein ingredient being used, and the incorporation of minor amounts of functional fiber ingredients were shown to greatly alter HMMA texture and anisotropy.

The concepts put forth here make significant practical contributions to the HMMA research field, and the results will be appreciated by industry personnel attempting to make or improve their own extruded HMMA products.

HMMA production, as well as to generate the most comprehensive publicly available overview of strategies to operate the cooling die unit operation to date.