Publications

Protein oxidation as an integrated aspect of plant protein-based food

Duque Estrada, Patrícia

Summary

Plant protein-based foods have gained a huge interest in the past years due to environmental and health reasons. A special category of food products has been developed to mimic animal-based products using plant proteins, known as meat analogues. The technological challenge is to make a structure similar to the natural fibrous structure in meat, while still delivering food with high nutritional value. High temperature-based processes have been used to reach desirable fibrous structures, but such process conditions induce physicochemical protein modifications that can reduce functionality and protein quality. Meat provides high quality proteins and is a source of a highly bioavailable iron form. The latter motives the incorporation of this micronutrient into meat analogues. The incorporation of the most bioavailable form of iron, water-soluble iron may, however, be hampered by its prooxidant activity, which can result in lipid and protein oxidation in the final product, altering the nutritional and sensory aspects. Therefore, the encapsulation of iron is often proposed to prevent oxidation reactions in fortified food. This thesis aimed to assess and control the protein quality in plant protein-based meat analogues, as a function of the presence of soluble iron as free or encapsulated form, and of the conditions applied for the structuring process. First, two methods of encapsulation were described. The effect of iron addition was compared to the effect of processing, regarding the occurrence of protein oxidation. Then the extent of protein oxidation over each processing step from the raw plant material, to the final product, was quantified. Lipid and protein oxidation were observed in iron encapsulates, but the subsequent application of iron in meat analogues had only a marginal effect on protein oxidation compared to that of the process conditions. Furthermore, the associated physicochemical changes due to protein oxidation and processing were not detrimental to gastric digestion in vitro. In this study, it has become evident that whatever the protein ingredient used, the application of a thermomechanical process to yield structured products systematically increased protein oxidation. We hope that the results of this thesis motivate not only further research on plant protein oxidation but also the need for less processed plant protein-based foods.