Germination and ultrafiltration modify the composition and functional properties of hemp seed protein isolates

Abstract

Ultrafiltration was investigated for its ability to alter the composition of hemp seed protein isolates (HSPI) and modify its functional properties. Hemp seeds that were germinated for 0, 1, 3, and 5 days underwent alkaline extraction and protein isolation by isoelectric precipitation (IP) or ultrafiltration (UF). UF processing with a 100 nm membrane resulted in the loss of off-color pigments as well as vicilin proteins and small peptides ∼9 kDa, which changed the physicochemical properties and functionality of HSPI. We found that HSPIs from UF were lighter in color and higher in protein purity than isolates from IP, but lower in solubility. Germination paired with UF increased the water holding capacity by 2.3 times, from 1.06 to 2.46 g water/g isolate, while oil holding capacity was unaffected by germination and UF. UF resulted in protein isolates with decreased foaming capacity and increased gelation concentration compared to IP, but 5-day germinated HSPIs had statistically unchanged emulsifying activity indexes between the two processing methods. Germination and UF are thus presented as clean-label processing techniques to modify the composition and functionality of HSPIs.