Enzyme-assisted oat protein concentrate development and wet extrusion: Summary of the doctoral thesis for the doctoral degree of science (Ph.D.) in engineering sciences and technologies = Enzimātiskā auzu proteīna koncentrāta ieguve un mitrā ekstrūzija : promocijas darba kopsavilkums zinātnes doktora grāda (Ph.D.) iegūšanai inženierzinātnēs un teholoģijās

The development of the doctoral thesis was carried out from 2020 to 2024 in the laboratories of the Food Institute of the Faculty of Agriculture and Food Technology of the Latvia University of Life Sciences and Technologies (LBTU), as well as in the Institute of Agricultural Resources and Economics (AREI), LBTU APP Institute of Horticulture, Latvian State Forestry Institute “Silava” and SIA “JP Biotechnology”. The aim of the doctoral thesis was to develop enzymatic water extraction methods for obtaining oat protein concentrate, to evaluate the functional properties of the obtained oat protein concentrates and to determine their suitability for further processing, including wet extrusion. Hypothesis: oat protein concentrate obtained by enzymatic water extraction followed by defatting can be used in wet extrusion systems. Theses that support the hypothesis: (1) oat protein can be extracted and concentrated by enzymatic water extraction; (2) degradation of non-starch polysaccharides during wet enzymatic hydrolysis does not affect the amino acid composition of oat protein; (3) ionic strength affects oat protein aggregation, which later affects its functional properties and protein recovery outcome; (4) defatting methods affect the functional properties of oat protein; (5) oat protein concentrate defatting improves the wet extrusion process. Research objects: whole grain oat flakes, finely ground oat flour, oat protein, oat protein extrudates. This study has the following tasks: (1) to identify methods that are suitable for the enzymatic water extraction of oat protein from industrial whole grain oat flakes and finely ground oat flour; (2) to identify suitable methods of defatting oat protein concentrates obtained from industrial oats and oat flour; (3) evaluate the redistribution of amino acids in the obtained oat protein concentrates and by-products, especially in fibre; (4) evaluate the characteristics of the obtained protein concentrates and study the functional properties of the obtained oat protein concentrates; (5) determine the extrusion parameters of oat protein concentrate; (6) study the physical properties of the resulting oat protein extrudate, including its structure, texture and colour. Research novelty: (1) methods have been developed for extracting oat protein concentrate up to 75% (dry matter) with the help of enzymatic water extraction; (2) the physicochemical properties, amino acid profile and functional properties of oat protein concentrates obtained by enzymatic water extraction have been evaluated; (3) technological parameters of wet extrusion of oat protein concentrate have been determined; (4) the physical properties of the oat protein extrudate obtained by the wet extrusion method have been investigated. The economic significance of this study: (1) the developed methods have proven the possibility of obtaining oat protein concentrates, which are considered as innovative raw materials, potential ingredients for a wide range of food applications, including "clean label" product categories; (2) the functional properties of the obtained oat protein concentrates allow manufacturers to determine the applicability of oat protein concentrates in their products; (3) the determined parameters of the extrusion process and the characteristics of extrudates obtained from oat concentrates help manufacturers to introduce innovations and new products, especially extrudates containing a new ingredient — oat protein concentrate. The thesis consists of three chapters. Chapter 1 describes the composition of oats, focusing mainly on the protein composition and the well-known methods of protein extraction and concentration. The review describes the protein's intrinsic properties, their interactions, and their performance during extraction and modification, including protein defatting. Attention is paid to the functional properties and applications of the protein. In addition, insights into protein modification to improve protein functional properties have been gathered Chapter 2 describes the methods and materials used in the work. Chapter 3 presents the results of the study, including oat protein extraction yields and functional properties of oat concentrates. The results also cover the field of oat protein extrusion, the parameters contributing to the extrusion and the textural properties of the obtained oat protein extrudate are indicated.