Grip on phenolics: Part of DFI-AF-19008 Biorefinery of protein containing biomass

As the protein transition seems to be becoming increasingly important, the demand for functional plant proteins will increase. Phenolic components are a broad class of molecules which generally react fast under the influence of light, enzymes and oxygen. When plant material is processed into a protein fraction or isolate, the phenols generally have a negative effect on the product properties in the sense of colour changes, reduced solubility, astringent or bitter taste, reduced digestibility and a reduction of functional properties. New protein production processes based on plants demand net insight in the removal of these phenols. Besides, the phenolic components could potentially have a value since their role in plants could be exploited in several applications. This project seeks to determine the most effective steps to remove the phenols and in parallel aims to valorise the phenolics fraction. In 2019 and 2020 this project investigated the role and interaction of phenols in the extraction and purification of proteins from plant sources. Furthermore, the valorisation of phenols as part of the biorefinery of protein containing raw materials was explored. In 2019 analytical methods were developed for measuring phenolic content and phenolic composition. Different approaches to reduce the phenolic content of protein extracts were investigated. Ultrafiltration and diafiltration proved to be very effective in obtaining protein extracts low in phenolics. Addition of a reducing agent, to limit binding of phenols and oxidation products to proteins, contributed to a higher protein yield and purity. In 2020 a protein extract from faba bean was produced using the approaches developed earlier in this project. Various protein functionalities were evaluated by comparison with industrial benchmarks. Secondly, a large batch of phenolics from rapeseed was produced and tested on properties (UV screening and antioxidant capacity) relevant for potential chemical applications. Application tests have been prepared at the end of 2020 and will be carried out in 2021. Furthermore, research was focused on the use of phenolics to decrease the rumen digestibility of ruminant feed. Procedures were developed for the crosslinking of different phenolics with feed protein, analytical methods were used to demonstrate the formation of protein-phenolics complexes, and in vitro tests were prepared at the end of 2020 to evaluate the digestibility of treated soybean meal samples (in collaboration with Wageningen Livestock Science). In 2021 this work will be continued with a focus on the following topics: − Functionality of protein extracts obtained from new sources (such as rapeseed and sunflower meal) using the same approach to reduce phenolic content; − Valorisation of phenolics as functional ingredient in chemical applications. Functional properties such as UV screening and antioxidant capacity will be evaluated in application tests; − Improved protein conversion in ruminants by using phenolics to make the protein fraction in animal feed (such as soybean meal) less digestible in the rumen, while still retaining intestinal digestibility.