Heat-induced gelation of faba bean and rice protein isolates with egg white powder and hydrocolloids : toward hybrid vegetarian sausages : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Auckland, New Zealand

Abstract

This thesis investigated the heat-induced gelation behaviour of two plant-based proteins, faba bean protein isolate (FBPI) and rice protein isolate (RPI), and their functional enhancement through the addition of egg white powder (EWP), modified waxy maize starch (MS), modified potato starch (PS), and methylcellulose (Me). The overarching goal was to develop gel matrices and sausage analogues with improved textural, rheological, and structural properties suitable for meat free alternatives. The experimental work was conducted in three stages. First, the minimum gelation concentrations (MGC) of FBPI and RPI were determined. Results showed that FBPI was able to form stable gels at 12% (w/w), whereas RPI required concentrations exceeding 15% (w/w) and exhibited limited self-gelling capacity. Subsequent, FBPI (12% (w/w)) and RPI (15% (w/w)) dispersions were blended with EWP across a range of ratios at pH 7 to investigate the synergistic effects between plant and animal proteins. Rheological analysis demonstrated that increasing EWP content significantly improved the storage modulus (G′) and reduced the loss factor (tan δ), indicating stronger and more elastic gel networks. Water-holding capacity (WHC), texture profile analysis (TPA), and SEM imaging confirmed that EWP incorporation led to firmer, more cohesive gels with finer, more homogenous microstructures. The second stage aimed to examine the integration of hydrocolloids (MS, PS, Me) into FBPI at 12% (w/w) and RPI at 15% (w/w) matrices to develop heat-induced composite gels. In FBPI systems, Me improved viscoelasticity, while starches contributed to firmness and WHC, with optimal results observed at 5% MS and 10% PS. RPI, which lacked intrinsic gelling capacity, responded more strongly to starch addition, particularly MS, which improved gel structure and stability even at lower concentrations. In the third stage, sausage formulations were developed with high (Me 1.6%, MS 5%, PS 10% (w/w)) and reduced hydrocolloid levels (Me 0.8%, MS 2%, PS 5% (w/w)). Sausages prepared with reduced hydrocolloid levels and supplemented with 8.8% (w/w) EWP (approximately 40% of total protein content) showed a significant increase in protein content and hardness Notably, improvements in chewiness was observed only in the FBPI-H-E sample. This research provides valuable insights into the development of meat free sausages with desirable textural properties, focusing on ingredient formulations and their effects on texture using FBPI and RPI. As sensory evaluation and flavour development were not within the scope of this study, further research is needed to address these aspects by incorporating flavourings to improve overall consumer acceptability.