Supporting UK malting barley with improved market intelligence on grain skinning

Spring barley grain destined for malting and downstream processes e.g. brewing and distilling must meet set quality requirements, including physical integrity, in order to optimise processing efficiency. If a batch of barley grain fails to meet malting specification, it may be rejected at intake. Intact barley grains have an adherent outer coat, or husk, enclosing the main body of the grain (the caryopsis). Good adhesion between the husk and the caryopsis is an essential grain quality requirement for the malting industry. Detachment, or loss, of the husk is an undesirable condition known as “grain skinning”; it causes significant handling and processing problems for maltsters, brewers and distillers, leading to inefficient processing and large financial costs. We report on wide variation in skinning susceptibility (from moderate to high) among barley varieties that had recently entered National List or Recommended List trials. Whilst evidence for genotypic variation in skinning is encouraging for future crop breeding and variety selection, our work confirmed that most current malting barley varieties are highly susceptible to skinning. The effects of agronomic inputs on grain skinning were considerably smaller than those associated with variety, growing season or crop handling (combine harvester settings). Fungicide treatments had no significant effect on skinning; this included crops grown with or without fungicide. Likewise, plant growth regulator had no significant effect on skinning. Effects of nitrogen fertiliser on skinning were small, but inconclusive. Skinning increased significantly in crops that were harvested late compared to those harvested early. This supports our view that crops with a later, or prolonged, ripening phase are at increased risk of skinning. Combine harvester settings had a significant effect on skinning; with increased drum speed and/or a reduced area for grain flow (tightening the concave) significantly increasing husk loss. There was no evidence for agronomic influences on grain size (weight) or specific weight being associated with differences in skinning. However, in some seasons, and under some growing conditions e.g. late sown crops, reduction in grain size and specific weight coincided with an increase in screenings and skinning. We conclude that variety choice, pre-harvest weather conditions and crop handling (combining) have significant influence on skinning, whilst routine agronomy has little or no effect.