Abstract: The effect of processing on thermal properties and in vitro digestibility of buckwheat protein (BWP) products were investigated. All the BWP samples exhibited two observable endothermic peaks with similar peak temperature (Td) values with the major peak at about 102 ℃ and the minor one at near 80 ℃. The two transition peaks observed may be attributed to 13S globulin with the Td near 102 ℃ and 8 S globulins with the Td near 80 ℃ respectively. The presence of high level of lipid (e.g. 17.8% in the FU-BWP) significantly decreases the enthalpy changes (ΔH) (p<0.05), and in some extent increases the ΔT1/2 (p<0.1) so as to suggest a decline of the extent of ordered structure. In simulated gastric fluid, the digestion pattern of BWP wasevidently different from that of SPI. In the pepsin digestion, the % N release of BWP increased more quickly than SPI at the beginning, but more slowly than SPI after 30 min. However, the % N release of BWP increases much faster than that of SPI in the trypsin-digested stage. This is because of different components of them and the presence of high activity of trypsin inhibitors in SPI. Most of the protein constituents of BWP globulins (including 13 S and 8 S globulins) are rapidly and completely hydrolyzed by pepsin within 1 min to form the protein hydrolysate products (with MW lower than 20 kDa), when 2 S albumins are almost intact during the whole pepsin digestion but hydrolyzed totally in the trypsin digestion. BWP with low lipid content shows high % N release in comparison with those with high lipid content(p<0.05). These results suggested that the digestibility of BWP can be associated with its lipid contents, which are affected by processing.

Key words: buckwheat protein(BWP), thermal denaturation, in vitro digestibility, processing