Electronic heating as a means of sterilizing potato bags contaminated with bacterial ring rot

Conclusions

A 30-minute exposure in a 2.45 megacycle, 3100-watt electronic oven was sufficient to kill all the ring rot bacteria in heavily contaminated jute strands placed throughout a bale of 100 bags. The maximum temperature reached within the bale was slightly over 270° F., at the center, but the bacteria were killed at a temperature of 230° F. at the outside. It has been shown experimentally that temperatures of over 300° F. and an exposure of 10 minutes are necessary to kill the organism (4). In the present trials, a temperature of 230° F. dropping to 169° F. over a 3-hour period killed all the ring rot bacteria. This inconsistency may be explained by the prolonged exposure to a lower temperature, or by the type of heating. High protein materials, such as bacteria, become heated more rapidly in electronic heating than do poor conductors such as jute strands. The temperature within the bale of bags would not, under the conditions of this experiment, truly represent the temperature to which the bacteria themselves were exposed. Although the relative humidity within the baled bags was not determined, water droplets collected on the sides of the oven during the treatment. The humidity during the treatments, may have, to some extent, influenced the rate at which the ring rot organism was killed. A recent publication by Richardson (5) indicates that high relative humidity has a marked effect on the susceptibility of the ring rot organism to heat treatment.