The influence of starch pasting properties and grain protein content on water uptake in barley

Steeping is the first operation of malting and its purpose is to increase the water content of the grain up to 43-46%; however, such a simple step encompasses several metabolic processes that affect germination and the final malt quality. The aim of this study was to evaluate the effect of initial grain protein (GP) content and starch pasting properties, measured using the Rapid Visco Analyser (RVA) on water uptake in different barley varieties. The partial least squares (PLS2) regression algorithm was used to compare the two data matrices, the independent block of variables X (RVA data and GP) and the dependent block Y (water uptake at different steeping times). The first two PLS2 loadings explained 65 and 23% of the total variation in water uptake in the barley samples. Water uptake at 1 and 2h was poorly explained by the PLS2 models, while after 5h the models explained more than 40% of the variability. The results from this study showed that, although a relationship between GP and water uptake exists, it is not universal for all the varieties, indicating that the relationship between GP and water uptake is varietal dependent.