Characterizations of Zein: Evaluating Functionality and Potential uses in Food Structuring
This thesis encompasses a thorough investigation in the potential use of zein networks as a structuring ingredient in plant-based meat and dairy alternatives. The popularity of plant-based products is continually increasing, however the majority of meat analogues and plant-based cheeses lack properties that are characteristic to the conventional products. Attempts to improve upon these products focused on the use of zein, a protein that had not been studied in this application previously. For the creation of whole muscle meat analogues, three techniques were developed to produce fibrous material from zein, either as fibrous networks or individual protein fibres. These techniques are: electrospinning, antisolvent precipitation of zein from ethanol using water and mechanical elongation of self-assembled zein networks. It was determined that the zein fibres produced were able to contribute a chicken-like texture to soy protein isolate gels when fibres were of uniform size and orientation. Despite this promising result, in depth investigation into the rheology of zein networks revealed inherently brittle behaviour, particularly when compared to the ductility of chicken muscle tissue. Efforts to reduce the brittleness of zein networks through enzymatic crosslinking with microbial transglutaminase proved unsuccessful and instead caused the brittleness of the network to increase even further. As an alternate technique, an increase in ductility was observed when zein networks were formed through antisolvent precipitation from acetic acid. Even further increases in ductility were achieved through antisolvent precipitation from ethanol. Throughout analysis, observations of softening and melting with increasing temperature were made. This led to the additional application of plant-based cheeses made with zein. Plant-based cheese samples containing a sufficient content of zein were shown to soften and stretch with increasing temperature in a statistically similar manner as conventional cheddar cheese. This result was emphasized further when currently available plant-based cheddar-style products were unable to stretch or perform with any similarities to conventional cheese. This research has therefore provided an increased understanding of the potential structural and rheological contribution of zein in food products. In addition, it provides the basis for the development and production of highly functional zein based meat analogues and plant-based cheeses.