Processing Oilseed By-Products for Improving Protein Quality and Functional Properties

Sustainable protein production for humans is a global challenge due to its impact on human health, society, and the environment. Some agro-industrial by-products are potential alternative protein sources, primarily depending on amino acid (AA) profile, protein digestibility, and functional properties. This study thermal processed oilseed by-products with microwave, conventional cooking, and ultrasound without using extensive protein extraction methods, evaluating in vitro protein digestibility (IVPD), AA composition and score, in vitro protein digestibility-corrected amino acid score (IVPDCAAS), and functional properties solubility, water- and oil-holding capacity, and foaming. In a screening step, five industrial by-products from flaxseed, pumpkin, sesame, grapeseed, and chia edible oil industries were characterized by proximate composition, AA profile, ANF content, and IVPD. Then, the selected flaxseed, pumpkin, and sesame seeds were processed, and treatment length, pH, and temperature impact on the IVPD were evaluated. Unprocessed oilseed by-products are rich protein sources (up to 40% on dry basis), and 70% to 85% IVPD. Temperature of 87.8 ºC and pH 8.0 were the best processing parameters, requiring 37 min of treatment to reach around 96% IVPD. Processing completely positively impacted the ANF content, inactivating the phytic acid and reducing trypsin inhibitory activity to 16% in the best case (no tannins were detected). Also, the evaluated heating methods reduced some essential AA in the samples. Nevertheless, processing did not decrease the amino score for the essential AA, except for the lysine content of sesame seeds, impairing the IVPDCAAS of this source. Lysine was the first limiting AA after processing the three samples. Processed samples demonstrated good protein solubility, foaming, and holding capacity. The evaluated by-products from the edible oil industry have great potential to become a viable alternative protein source for food formulation systems. All the evaluated thermal processes enhanced the protein digestibility and reduced ANF content.