Functional Properties of Buckwheat (Fagopyrum esculentum Moench) Seed Protein Isolate: Effects of Limited Enzymatic Hydrolysis with Trypsin

The effects of limited enzymatic hydrolysis with trypsin on the physicochemical and functional properties of buckwheat protein isolate (BPI) were investigated. The protein constituents, free sulfhydryl (SH) contents and surface hydrophobicity (Ho), as well as some selected functional properties, such as protein solubility (PS), emulsifying (including emulsifying activity index, EAI and emulsion stability index, ESI) and foaming (including foaming capacity, FC and foam stability, FS) activities of BPI hydrolysates (freeze-dried) were evaluated. The influence of heat treatment prior to freeze-drying on these properties was also evaluated. The limited hydrolysis led to transformation of insoluble aggregates into soluble peptide fragments. Progressive decreases in total SH content (or exposed free SH content) and Ho were observed for both untreated and heated hydrolysates with the increase in degree of hydrolysis (DH). In the unheated case, the hydrolysis treatment resulted in gradual increases in PS, EAI and ESI, and decreases in FC and FS of BPI. The heat pretreatment remarkably decreased the EAI and ESI of the hydrolysates, but significantly increased the FC for the hydrolysates with DH less than 8.3%. The results indicated that the limited hydrolysis with trypsin could be applied to modify the physiochemical and functional properties of buckwheat proteins. _____________________________________________________________________________________________________________