Optimization of hemp protein isolate production and glycation by response surface method (RSM)

Today, vegan diet culture has become quite widespread. Therefore, interest in plant-based protein sources is increasing day by day. Industrial hemp seed, one of the plant-based protein sources, contains high quality oil, protein, carbohydrate, insoluble fiber, vitamins and minerals. It is known that hemp seed protein has a nutritional value comparable to egg white and soybean proteins due to its excellent digestibility and sufficient essential amino acid content. In this study, optimization was applied with response surface method (RSM) to obtain the highest yield protein isolate from defatted hemp seed under different extraction conditions. Optimum extraction conditions were determined when salt concentration was 0, pH value was 12 and temperature was 49 ºC. Protein isolate produced under optimum conditions was subjected to glycation process and glycation conditions were also optimized with RSM. The optimum conditions for glycation, where the most suitable glycation degree and browning index were obtained, were determined as protein:sugar (fructose) ratio of 1.6:1, temperature of 60 °C and time of 90 min. Under these conditions, no statistical difference was found in emulsifying activity index and emulsion stability index results of glycated protein isolate obtained from non-glycated protein isolate. In total phenolic-flavonoid compound and antioxidant activity amounts, sugar complex caused a decrease in these values. In addition, it was determined that there was a high positive correlation between total phenolic-flavonoid compound and antioxidant activity values. SEM micrographs showed the existence of relationships between hemp protein isolate and sugar and these interactions led to a spongy three-dimensional microstructure. According to FTIR results, it was determined that glycated isolate showed stronger absorption at 3300-3200 cm-1 compared to non-glycated isolate. This is an indication that the reducing end of the polysaccharide chain is covalently combined with amino acids. As a result, this study has determined important findings in terms of functional and characteristic properties on how monosaccharides affect glycation.