Effect of methods of analysis and heat treatment on viscosity of wheat, barley and oats

The purpose of this work was to study variation in viscosity of different grain samples using different extraction methods, and to study effect of heat treatment on viscosity. A total of 80 samples of wheat, oats and barley harvested at two locations were analysed for physical appearance, fibre content, and in vitro viscosity using water (WEV), acidic buffer (AEV), HCl/NaHCO3 buffer with pepsin and pancreatin added (IDV) or the Avicheck™ method (FFV). A transformation where the natural logarithm of the relative viscosity value was divided by the concentration of the sample in liquid was shown to give stable values over a wide range of sample concentrations in liquid for WEV and IDV. Barley and oats had similar viscosities although there was considerable variation between samples, while viscosity was much lower and with less variation between samples for wheat. Heat treatment in an autoclave at 100°C for 5 min increased WEV for all samples, but IDV increased for oats only as a consequence of heat treatment. Although WEV was much lower than IDV, the correlation between these two viscosities was high (0.95, P<0.05) for barley and moderate (0.68 and 0.69, P<0.05) for wheat and oats. A moderate to high significant correlation existed between viscosity and soluble fibre content for barley.