Maintaining acceptable microbial quality of grains is a major challenge.  Grain contains a wide assortment of micro-flora including bacteria, mold, and yeast.  The micro-flora may be active under some processing conditions; thus, processors have set stringent microbial limits on the grain products they accept.  Ozonated water is reported to be effective in reducing microbial load in foods such as fruits and vegetables.  Ozonated water may be an effective alternative to chlorine in treating durum used for pasta, barley used for malt, and other small grains, thereby increasing the value of grain.

A baseline system has been developed which includes an oxygen concentrator, gaseous ozone generator and monitor; a system for producing, monitoring and handling ozonated water from gas; and a system for spraying a controlled amount of ozonated water into a bed of fluidized (agitated) grain.   All ozone-contact surfaces were fabricated from ozone-compatible materials, and the exhaust from the system will be routed through an ozone-destruct module.   Ozone Discovery Badges are used in the work area to monitor ozone levels.  Process variables for treating grain samples typically include dissolved ozone concentration, acetic acid concentration,  water:seed ratio, and fluid bed-sprayer configuration.  APC (aerobic plate count) and YMC (yeast and mold count) are performed immediately using APC and YMC Petrifilms.

Ozonated water showed a pronounced antimicrobial effect only when used in combination with 1% acetic acid. Although acetic acid does not have residue issues, as chlorine does, future research should be conducted to strive to eliminate microbes using ozonated water alone or with a minimum of other agents. Ozonated water alone can have a significant antimicrobial effect if used at higher dissolved ozone concentration. Knowing current system performance and how it relates to system design, it is possible to achieve even higher dissolved ozone concentration, for example, by increasing gaseous ozone concentration.