Functional properties and in vitro digestibility of buckwheat protein products:: Influence of processing

The effect of processing on some functional properties and in vitro digestibility of buckwheat protein products (BWP) was investigated. In the spray-dried cases, the protein solubility (PS) of BWP was much greater than that of commercial soy protein isolates (SPI) at below pH 5 and above pH 6 (P < 0.05). At below pH 7, the PS of those BWPs by ultrasonic-assisted extraction was higher than that by mechanical extraction or by ultrasonic-assisted extraction and additional de-fatting treatment. The water holding capacity of those BWPs obtained by freeze-drying was also significantly higher than that by spray-drying (P < 0.05). The fat adsorption capacity of freeze-dried BWPs was significantly higher than that of SPI and those spray-dried BWPs (P < 0,05). The emulsifying activity index (EAI) of some spray-dried BWPs was higher than that of SPI at below pH 4 and above pH 6, while the emulsion stability index (ESI) was lower than that of SPI at below pH 7 (P < 0.05). The de-fatting pretreatment could improve the EAI and ESI of BWP, especially at above pH 6. In simulated gastric fluid, the digestion pattern of BWP was evidently different from that of SPI. In the pepsin digestion, the % N release was affected by the processing. The BWPs with low lipid contents had higher % N release as compared to those with high lipid contents. These results suggested that the functional properties and in vitro digestibility of BWP be associated with its lipid and ash contents, which could be affected by processing. Thus, functional and nutritional BWPs, potential for food applications, can be produced through controlling the processing. (C) 2007 Elsevier Ltd. All rights reserved.