99D-26

Oatmeal and oat flour have been used in the production of baby food cereals for many years.  The microbiological quality of such products must meet stringent regulatory standards for consumption.  As a low acid food product, infant cereals are susceptible to flat sour spoilage which is caused by the thermophilic sporeformer, Bacillus stearothermophilus.  Because of its heat-resistance, elimination is almost impossible using conventional treatments. 

As an alternative, superheated steam sterilization was examined for its lethal effect on B. stearothermophilus spores exposed to superheated steam. 

Sterilized oat groats were inoculated with prepared Bacillus stearothermophilus spores and subjected to superheated steam at 115 – 170 ^oC with varying velocities for 2 – 40 minutes. Preliminary studies suggested that superheated treatment at 145 ^oC, with velocities of 0.52, 1.10 and 1.53 meters/sec(m/s) were the most practical parameters in reducing the number of spore survivors on oat groats, and yielded oat flour of acceptable color and textural properties.   

At the lowest velocity there was a steady decline in survivors over 40 min, resulting in a 5-log reduction. On the other hand, the highest velocity resulted in a greater number of spore survivors, with a 3.5- log reduction at the end of the run.  However at the medium velocity of 1.10 m/s, the spores were completely destroyed within 30 min of exposure to the superheated steam.  The highest and lowest flow rates reduced the lethal effects of the treatment at 145 ^oC.  At 145 ^oC, the best kill was achieved at a steam flow of 1.10 m/s, with the next best occurring at the lowest velocity of 0.52 m/s.

Superheated steam can be used to reduce Bacillus stearothermophilus spores and render a safe product to consumers.