A series of thermal destruction studies of the most heat resistant yeast strain No. 15 among 61 isolates were conducted in order to establish the optimum pasteurization condition of peach solid pack. The results obtained are summarized as follows:
1. A survival curve of the selected yeast strain No. 15 at 58℃ consisted of heat labile and heat stable fraction, showing broken curve.
2. The actively growing cell showed less recovery rate than 10 day rested cell after agitatien-growing for 90 hr. For heating menstrua, peptone solution gave higher recovery rate than peach juice. For recovery medium, YM agar gave higher recovery rate than peach juice agar. The selected yeast was more resistant to heat at pH 4.0 than at pH 3.5 in both heating menstrua and recovery medium.
3. Z value of TDT curve of the selected yeast (heating : at pH 3.5 in peach juice. recovery: at pH 3.5 in peach juice agar) was 4.8℃.
4. The selected yeast No. 15 was identified as Torulopsis candida.
5. In the inoculated pack test of 4 oz can, it was concluded that the optimum P.U. 70/5 was 168 (center temp; 78.5℃, initial temp; 18℃, processing time; 18 min, initial yeast count; 1.0×10^7 per can).
|