The heterogeneous distribution of α-amylase and endoxylanase activity over a population of preharvest sprouted wheat kernels and their localization in individual kernels

To develop targeted approaches to improve the quality of preharvest sprouted (PHS) wheat as a raw material for food manufacturing, knowledge on the nature and distribution of hydrolytic enzymes in PHS wheat is crucial. Results of the present study indicate that α-amylase and endoxylanase activities are heterogeneously distributed among a population of PHS kernel. Within individual severely sprouted kernels, the enzyme activities are heterogeneously distributed throughout the different tissues. α-Amylase activity, almost exclusively of endogenous nature, is mainly detected in the germ region and to a lesser extent in the aleurone layer. Endoxylanase activity is predominantly of microbial origin and located on the kernel surface. In spite of this, light and epifluorescence microscopy show decreased kernel integrity and cell wall breakdown in the crushed cells layer, the endosperm, and the aleurone layer in a selection of kernels upon preharvest sprouting. This knowledge offers opportunities for the development of treatments to reduce the enzyme load in PHS wheat at postharvest level to improve its flour quality.