Phosphorylated Modification and Functional Properties of Prolamin from Baijiu Distiller's Grains

Distiller's grains are the major by-product in spirits industry. Baijiu distiller's grains after fermentation and distillation are rich in prolamin. However, the poor water solubility of prolamin from distiller's grains (PDG) limits its further application. In this work, PDG was extracted by ethanol-alkali method and phosphorylated with sodium tripolyphosphate (STP). Furthermore, the effect of phosphorylation on the functional properties of PDG was evaluated by water solubility, water holding capacity, oil holding capacity and emulsion capacity. The results showed that PDG extracted by ethanol-alkali method was mainly composed of four proteins with different molecular weights. The extraction rate of PDG was affected by the crushing degree of distiller’s grains powder, and small particle size was conductive to improve the protein extraction rate. The extraction rate of PDG reached 22.69%±0.26% when the powder was 200 mesh. The differential scanning calorimeter results indicated that PDG possessed good thermostability with the denaturation temperature of 123.47 ℃. Fourier transform infrared spectrometer (FTIR) results showed that PDG was modified with phosphate groups after reaction with STP. The water solubility of PDG after phosphorylation was improved and it was 3.53 times higher than that of PDG, reaching 943.08±16.04 μg/mL at 30 ℃. Due to the combination of phosphate groups, the functional properties of PDG were significantly improved. Compared with PDG, the water holding capacity and oil holding capacity of phosphorylated PDG at 30 ℃ were increased by 44.9% and 33.8% respectively, and the emulsifying property and emulsifying stability at pH10 were increased by 54.9% and 3.6 times respectively. The improvement of the functional properties was conductive to the expansion of PDG's application fields. This work laid a foundation for the high added-value utilization of distiller's grains.