Measurement of Heat Damage in Wheat by Assessment of Protein Fibril Formation

Abstract

A simple and rapid screening test has been developed for detecting heat-damaged wheat. A small amount of endosperm material, obtained by milling or grinding samples or crushing individual kernels with a hammer, is placed upon a microscope slide and wet with a drop of water. Upon wetting, protein fibrils are rapidly formed and these can be viewed at 100 × magnification by bright field microscopy. Heat damage to the sample reduces the fibril formation and thus heat damage can be determined by assessing the extent of protein fibril formation. Three samples of Canada Western Red spring and two samples of Canada Prairie Spring wheat were heat treated at 65°C and 70°C for 0, 2, 4, 8 and 16 h to obtain a range of heat damage as determined by changes in physical dough (Mixograph) properties. Following heat treatment, samples that displayed normal dough properties showed extensive fibril formation while samples that were rated as 'damaged' by the Mixograph procedure showed little or no fibril formation. Samples that were rated as 'seriously reduced' in quality showed an easily recognizable reduction in the degree of fibril formation. In addition to being simple and rapid, the method has the additional potential that equipment requirements can be minimal, inexpensive and highly portable. While a research-quality microscope was primarily used for this investigation, the clarity of fibril formation and low magnification required for observation suggest that an inexpensive low-power microscope would be satisfactory. This procedure requires little technical training when reference photographs are used.