IMAGE-ANALYSIS OF GRAIN AND CHEMICAL-COMPOSITION OF THE BARLEY PLANT AS PREDICTORS OF MALTING QUALITY IN MEDITERRANEAN ENVIRONMENTS

We have explored the possibility of predicting the malting quality of barley grain, indicated by malt extract yield, by characteristics meas ured either on plants at anthesis or in mature dry grain by image anal ysis. To produce barley samples with varying levels of all the charact eristics studied, we used grain from an experiment designed to study t he influence of low-input husbandry practices on malting quality of ba rley by growing five malting genotypes at each of four environments (s ite x season) and with two different agronomic treatments (N fertiliza tion and herbicide-mechanical roguing of weeds). The results showed th at nitrogen content in the plant at anthesis was a good predictor of g rain protein content, this characteristic in turn being positively cor related with embryo size and grain volume, as estimated by image analy sis, and negatively correlated with nonstructural carbohydrate content in the plant at anthesis. Extract yield was positively correlated wit h Kolbach index (ratio of soluble to total wort protein) and negativel y correlated with wort viscosity and barley grain protein content. Thu s, the only practical predictor of malt extract was grain protein cont ent.