Effect on malt quality from physical treatment of the barley. part ii. squeezing and freezing barley grains.
Powell, G.E. and Barrell, G.W.
Whilst good quality malt can be produced from barley by the use of multiple steeping sequences and germination in less than 55 hours process time, excluding kilning, if the grains are subjected to gentle squeezing or to freezing, under the appropriate conditions, during multiple steeping sequences, the resultant malts give higher extracts than those from control malts. Increases in extracts as compared with controls, have been ca. 1 lb/qr for samples which have been subjected to freezing. Such operations appear to increase the amount of starch available for enzymic degradation as a result of physical rupture of protein matrices surrounding some of the starch granules which might not be available for attack during conventional malting and mashing operations. In the multiple steeping sequences investigated, squeezing at the end of the second air rest and freezing during the 3rd immersion leads to malts with the highest extracts. At such times of squeezing and of freezing, any damage to the aleurone should have little effect on modification of the grain. Freezing periods for longer than 2 hours should be avoided during rapid malting processes, as the resultant malts have lower extracts than controls, possibly due to enzyme inactivation. Similar effects result from squeezing grain at narrow roller settings viz. less than 2 mm.
Keywords: barley freezing germination malt malting quality steeping