Modification of structural and functional properties of selected fruit, vegetable, and grain by-products via extrusion processing

In recent years, the increased consumer awareness and demand for natural, health-promoting, and sustainable foods has driven the research for alternative resources. With this, by-products from fruit and vegetable processing, such as apple pomace, have gained significant attention as novel and economic sources of dietary fibers and phytochemicals. In addition to its nutritional value, apple pomace has a range of functional properties such as water binding, gelling and thickening properties. Therefore, it can be used not only to fortify but also to structure food products and beverages. However, depending on the application, the apple pomace must often be modified to achieve the desired functionality in foods. Recently, extrusion processing has gained significant attention due to its ability to modify biopolymers in a flexible, environment-friendly, and sustainable manner.

Only a few empirical studies dealt with the functionalization of by-products by extrusion processing. However, the interrelation between process parameters, process conditions, resulting changes in structure and chemical composition, as well as changes in functional properties as water binding, water absorption, as well as thickening properties, were unknown. For targeted modification and the transfer of knowledge to a wide variety of raw materials, the understanding of these interrelations was necessary. Besides this, the study focused on the impact of the role of thermal and mechanical stresses on the functionalization as well as the pre-treatment and the nature of the raw materials.

This study aimed at a detailed and comprehensive understanding of the functionalization of food by-products via extrusion processing and its impact on functional and rheological properties. This information is essential for upcycle food by-products, designing functional ingredients and innovative food formulations.