MALT PASTEURIZATION: STERILIZATION OF BARLEY MALT WITH GAMMA RADIATION
Off-flavored distillates are occasionally produced during the processing of grain mashes to beverage alcohol which can be traced to metabolic activities of bacteria that survive the saccharification step in mashing in which the mesh is maintained at 145 deg F for a short time. Barley malt is the principal source of these bacteria, which are mainly lactobacilli; therefore, attempts were made to sterilize the malt by Co/sup 60/ gamma irradintion. It was shown that 0.112- Mrad irradiation reduced the bacterial counts of malts to very low levels whereas no significant reduction in alpha -amylase or alcohol yields occurred. Higher dosages of radiation resulted in substantially complete sterilizntion of the malts but also in some destruction of their amylase activities. Pre-irradiation of malt caused progressively lower maximum bacterial populations and lengthened lag phases as more radiation was used; however, the rate of multiplication in the exponential growth phases was not influenced by the amount of radiation. Heating subsequent to irradiation has been shown to have a synergistic lethal effect on bacteria, but no significant difference between irradiated and nonirradiated malts or of saccharificntion temperature upon alcohol yields was found. In some trials, higher alcohol yields were obtained from irradiated malts used at a saccharification temperature of 125 deg F, suggesting that some destruction of malt amylase occurs by saccharifying at 145 deg F. Results using malts treated with gamma and cathode rays are compared. A 1% reduction of alcohol yield was caused by 0.4 Mrad of cathode rays and by 1.1 Mrad of gamma rays. Beyond the amount of radiation causing 1% reduction, the yields drop rapidly with either kind of radiation. The alpha -amylase content of malt is not significantly reduced by irradiation with less than 0.04 Mrad of either gamma or cathode rays, Beyond 0.04 Mrad, however, the alpha -amylase content decreases rapidly with both kinds of radiations, no significant difference being apparent between the action of gamma and cathode rays on this enzyme. It is estimated that the cost of pasteurization of grain using 0.1 Mrad Co/sup 60/ irradiation would be approximately ton. (BBB)
- Research Organization:
- Univ. of Michigan, Ann Arbor
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-18-015841
- OSTI ID:
- 4078271
- Journal Information:
- J. Agr. Food Chem., Vol. Vol: 12; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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