Mechanisms of Malt Extract Development in Barleys from Different European Regions: I. Effect of Environment and Grain Protein Content on Malt Extract Yield

Abstract

Malt extract yield (EXT) and barley protein content (BPROT) data from 346 EBC trials located across all the EBC countries, and composed of many different varieties, from the years 1980, 1982 to 1990, inclusive, and 1993 to 1995, thus covering 13 seasons, were used to detect regional trends affecting the negative correlation between these two variables. Quadratic curves were fitted to data from each European region (North, Central, West and South), all of which showed very high coefficients of determination (r2). A common trend in all regions, and also in the overall European analysis, was of EXT decreasing when BPROT increased, although the extent of decrease varied among the regions. Two different geographical patterns of variation in EXT with changes in BPROT have been observed, on the one hand those of the Iberian Peninsula and West region, and on the other, those of the North and Central regions. In the first case, the rate of decrease in EXT was almost constant across the full range of variation of BPROT, whereas, in the second case, the decrease in EXT grew progressively with increases in BPROT. Therefore, although “Bishop's law” on EXT decrease with BPROT increase holds true as a general statement, it would be necessary to take climatic differences into account when estimating EXT values from BPROT data.