Functionalisation strategies for plant proteins in meat analogues and solubility-dependent food applications

This study aimed to enhance the functionality of plant proteins in food applications, focusing on solubility-dependent properties and fibrous structure formation in meat analogues produced by high-moisture extrusion processing. Plant protein ingredients are sustainable and healthy alternatives to their animal counterparts, but they often have limited functional properties. This research investigated various plant protein isolates and concentrates, including rice, pea, and wheat protein isolates, as well as pea, oat and rapeseed protein concentrates. These concentrates, produced through energy-efficient dry fractionation, also of-fer additional health benefits by increasing dietary fibre intake. Strategies to improve plant protein functionality included limited enzymatic protein hydrolysis to improve foaming, gelation, and colloidal stability of rice proteins, and chemical pH-shifting to acidic and neutral conditions to enhance fibrous structures of rice, pea, and wheat proteins. Different enzymatic crosslinking and deamidation treatments were applied to oat proteins, while acidification using fermentation was investigated to tackle sensory challenges in rapeseed ingredient. The findings of this study showed that limited hydrolysis improved functional properties of originally insoluble rice proteins, with a 1.5-1.8% degree of hydrolysis being generally preferable, especially for foaming and gelation. The choice of enzyme significantly influenced the outcomes, even with similar degrees of hydrolysis. The pH of the raw materials played a crucial role in fibrous structure formation during high-moisture extrusion processing. Neutral pH conditions enhanced structure formation in rice, wheat, and pea proteins due to the increased disulphide bond reactivity at higher pH levels, which was independent of the isoelectric point of the raw material. Successful fibrous structure formation in oat protein concentrate required a combination of pre-heating, deamidation, and cross-linking, highlighting the complex interplay between starch and proteins, as it was discovered that when starch was degrades, the fibrous structure formation was not induced. Furthermore, related to rapeseed, it was found that acidification, whether involving fermentation or incubation, negatively impacted fibrous structure formation, with different strains producing varied outcomes. While fermentation reduced unwanted chemical flavour and odour in rapeseed ingredient, it introduced proteolysis leading to intense bitterness and loss of fibrous structure. Chemical pH-shifting alone was removing the chemical flavour without introducing bitterness or loss in structure, suggesting it as a viable strategy for functionalisation in meat analogue applications. These results underscore the potential of the used strategies to accelerate the use of plant proteins in meeting the growing demand for sustainable and healthy food products. By using these strategies, this research contributes to the development of more appealing and sustainable plant-based alternatives, supporting both environment and consumer health.