| Abstract [eng] |
The production of rice drink produces large amounts of by-products - rice press cake. This by-product of food is not rationally used, it is usually used for feed or disposed of. For this reason, the development and implementation of technologies such as the valorisation of by-products into higher value-added food components is becoming relevant not only at the national or regional level, but also at the global level. According to the literature, rice cake contains valuable proteins that are nutritious and suitable for people with allergies. The aim of the final work is to improve the optimal extraction conditions for maximum protein extraction from rice press cake (RI) and to evaluate the functional and gel-forming properties of the extracted proteins and to create a scheme for the production of protein isolates using biotechnological methods. In the final work, the enzymes were selected and the enzyme composition was formed to increase the protein extraction from RI, the water and oil absorption capacity, emulsion and foaming ability and stability of the obtained proteins were evaluated. For gel formation, proteins were modified by sonication and enzymatic transglutaminase or proteinase treatment. The results showed that most of the protein from RI could be extracted (2,104 mg/ml) by alkaline extraction at 60 ºC at pH 10 and a dry matter to water ratio of 1:4. Protein recovery from RI can be increased to 71 % by hydrolyzing an enzyme composition consisting of amylase, cellulase, and protease. Hydrolysis of the enzyme composition slightly (2,5 %) reduced the volume and stability values of the protein foam compared to the crude RI proteins. The use of a protease and enzyme composition for RI treatment increased the oil absorption capacity (AAG) by 66 % and 67,4 %, respectively, however, the composition of the treated enzymes and the control sample absorbed less water (VAG 61,1 % and 63,2 %, respectively) compared to the protease-treated proteins (64,3 %). Gel texture analysis of rice protein isolate (RBI) showed that using a protease under optimal conditions could yield a harder and stronger gel than using transglutaminase. At a protein concentration of 20 % and a protease content of 800 AV/ 100 g, a mass of maximum viscosity was obtained and a gel of maximum hardness was formed. The use of transglutaminase increased gel cohesion and viscosity index. No significant differences between results were found with TG at different enzyme and protein concentrations. High-intensity ultrasonic treatment of rice proteins and modification of proteins with proteolytic enzymes allowed the formation of a more stable and stronger gel structure. Analysis have shown that enzymatic hydrolysis is an efficient way to extract valuable proteins from rice bran, and ultrasonic treatment can be used effectively for the production of functional foods. |
