When malt was kilned with natural gas containing no sulphur the appearance and certain properties were defective and it has been the practice to burn sulphur in natural gas firing, but alternative treatment with sulphuric or sulphurous acid is now suggested. In 7 trials, H2SO4 of 66 degrees Be at rates of 36 to 183 lb per 1000 bushels of barley was directed in a fine spray over green malt while passing on a conveyor belt to the kiln. The rolling of wet grain on the conveyor gave complete dispersion of the acid so that after kilning the grain showed no charring or magpie effect but had a much brighter appearance. Wort from these malts showed slightly higher extract and soluble proteins with pH 5.0 to 6.0. In pilot scale plant, SO2 was injected into the piping system used for watering the germinating grain at rates of 24 to 96 lb SO2 per 1000 bushels of barley. Injection 48 h before kilning was too early; injection of 36lb at 15 h before kilning gave best results. This did not interfere with germination but gave a marked reduction in the bacterial contamination of the green malt. the appearance of treated kilned malt was much improved. Worts prepared from treated malts showed higher extract and soluble proteins with slightly reduced pH. Evolution of SO2 from the malting bed fell to 1 ppm at 7 to 15 h after treatment and an alkaline spray in the germination air exhaust is recommended to prevent atmospheric pollution.
Keywords: effluent extract germination kilning malt malting protein sulphur dioxide sulphuric acid