Valorization of plant-based protein-rich byproducts through physical processing techniques: A review

The global rise in protein demand has generated a pressing need to explore sustainable sources such as protein-rich byproducts. Although commonly utilized as animal feed, these byproducts hold significant potential for valorization into functional ingredients. However, their use is hindered by challenges, including their limited functionality, undesirable texture, antinutritional factors, and unappealing flavor and odor. Particularly, their diminished ability to form stable emulsions, gels, or foams greatly limits their application in food. Additionally, the presence of insoluble fiber in byproducts can interfere with their ability to blend seamlessly into formulations, while antinutritional factors can negatively impact their nutritional value and bioavailability. Physical processing techniques offer promising solutions to these challenges by enhancing techno-functional properties of proteins (e.g., solubility, water-holding capacity, emulsifying capacity), reducing antinutritional factors (e.g., phytates, trypsin inhibitors), converting insoluble fiber to soluble forms, and improving protein bioavailability. These enhancements render these byproducts viable alternatives for food ingredient applications. The examples of processing techniques discussed in this review include high-pressure processing, ultrasound, pulsed electric field, cold atmospheric plasma, and extrusion. Among them, extrusion holds particular importance due to its dual role in modification and product development. The application of novel physical processing techniques has shown promise in improving the functional properties and digestibility of protein-rich byproducts. Investigating the effects of these techniques on the entire byproduct could potentially save time and resources spent on protein extraction. It is also essential to implement specific safety regulations for the use of byproducts to ensure consumer safety.