Optimization of Hemp Seed (Cannabis sativa L.) Protein Extraction and Glycation Conditions by Response Surface Methodology: Physicochemical, Functional, and Thermal Characteristics

In this study, first, optimization using the response surface method was implemented to obtain the highest yield of protein isolate from defatted hemp seed under different extraction conditions. Optimum extraction conditions were determined with 0% salt concentration, 12 pH value, and 49°C temperature. The protein isolate produced under optimum conditions was subjected to the glycation process, and the glycation conditions were also optimized. The optimum conditions for glycation were determined as a protein isolate: sugar ratio of 1.6:1, temperature of 60°C, and time of 90 min, providing the most suitable glycation degrees and browning indices. There was no statistical difference between the glycated protein isolate obtained under these conditions and the nonglycated protein isolate in terms of emulsifying activity index and emulsion stability index. For total phenolic–flavonoid compounds and antioxidant activity, the sugar complex caused a decrease in these values. In addition, there was a high positive correlation between bioactive compounds. SEM micrographs showed relationships between hemp seed protein isolate and sugar, and these interactions led to a spongy three-dimensional microstructure. When the FTIR results were analyzed, the glycated isolate had stronger absorption at 3300–3200 cm−1 compared to the nonglycated isolate. In conclusion, this study reports important findings in terms of functional and characteristic properties of how monosaccharides affect glycation.