Effect of different heating conditions on the extractability of barley hordeins.

The extractability of hordeins from barley grains was investigated after wet and dry heating conditions. It was found that the amount of hordeins extractable with 55% 2-propanol decreased in a time-dependent manner after barley grains were steamed (wet heating), whereas hordeins showed no effect from heating in an oven at 100 degress C for up to 120 min (dry heating). The result of SDS-PAGE analysis revealed that B-hordein decreased time-dependently in extractability with wet heating and had almost completely disappeared by 60 min, but C-hordein remained unchanged until 120 min. With the use of the hordein fraction prepared from the nonheated barley grains, it was confirmed that B-hordein suspended in boiling water lost solubility in 55% 2-propanol. The insolubilized B-hordein was redissolved by the addition of 2-mercaptoethanol to 1%, which suggested that the intermolecular disulfide bonds would play a significant role in the loss of solubility. On the other hand, C-hordein did not lose solubility from being heated under the same conditions.