Insoluble residues from soybean, rice, oat and almond -based beverage: Landscape of the product category, chemical characterisation and valorization in the food industry

Background: Plant-Based Beverages (PBBs) are beverages obtained through the extraction of plant material such (i.e. legumes, grains, nuts). The PBBs production process yields organic by-products, mainly insoluble residues (IR) from the solid/liquid separation step. Except for the IR from soybean (okara), the data on IR composition are scarce. Scope and approach: This work investigates the nutritional composition of IRs and proposes their valorization in the food industry. PBBs from soybean, rice, oat and almond were considered as the most representative examples of legumes, cereals and nuts-derived products, respectively. The IR chemical compositions and functional changes that occurs especially in the protein are discussed with regard to their use for the production of fermented bioactive compounds or as bakery- and protein ingredients. Key findings and conclusions: IRs from nuts, legumes and grains have a different composition. The PBB production process yields IRs rich in fiber and fat, while most of the carbohydrates are extracted. The protein fraction behaves differently depending on its solubility the process. In the case of the cereals, proteins are significantly concentrated in the IR (+7.4 and + 2.4 for rice and oat respectively). All the IRs considered can be up-cycled in food industry. IR from soybean, oat and rice seem to be suitable for the production of bioactive ingredients for functional food production; almond, soybean and oat IR can be used as flour base for bakery. IR from rice may be a good candidate to replace soy protein isolates/concentrates for plant-based meat production.