Changes in wheat protein aggregation during grain development: effects of temperatures and water stress

Abstract

In mature wheat ( Triticum aestivum L.) grains, the distribution of the monomeric and polymeric proteins as well as their solubility play a critical role in governing wheat flour properties and uses. The contents of SDS-soluble and SDS-insoluble proteins and their ratio are useful criteria to evaluate the technological properties of the flour. The ratio depends on the protein composition, mainly genetically controlled and on the environmental conditions, such as temperature and water stress during grain filling. In this study, we evaluated the effects of temperature and water availability on the SDS-soluble and SDS-insoluble protein accumulation measured by size exclusion HPLC. The quantities of soluble and insoluble proteins increase until 400–500 °Cd. The rate of accumulation of soluble proteins was about 60 fold higher than the rate of the insoluble. After this, there was an insolubilisation of the soluble fraction and a rapid decrease to about 10 of the soluble to insoluble ratio. Temperature and drought did not affect the rate of soluble and insoluble protein accumulation per degree-day, and the same equations can be used in a modelling approach. In contrast, the rate of accumulation per day increased with the temperature but was not modified by drought. The insolubilisation and the rapid increase of the insoluble proteins occur concomitantly. The temperature did not modify the onset of the rapid insolubilisation, whereas in drought conditions this occurred earlier. We concluded that this time corresponded to a key stage of the grain development under genetic and environmental control, and this key stage was probably linked to the water dynamic in the grain.