• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.318-328
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• 1987

The results of experiment to review the optimum pasteurization condition for the raw milk produced in Korea by using UHT procedure of $100-145^{\circ}C$, the changes in chemical composition, microbiological aspects and the keeping quality of the heat treated milk are summarized as follows: 1. In UHT milk sterilized at $100-145^{\circ}C$, the pH value decreased from 6.55 to 6.33 but protein, fat, lactose and ash did not show significance changes while casein nitrogen and non-protein nitrogen increased but non-casein nitrogen and filterable nitrogen decreased. 2. Calcium content decreased gradually from 119.8 mg/100 g of raw milk to 75.75 mg/100 g at $145^{\circ}C$ as the heat treatment increased and vitamin C decreased rapidly from 1.37 mg/100 ml to 0.82 mg/ 100 ml while artificial digestibility increased from 14.07% of raw milk to 26.0% as the heat treatment increased. 3. As the heat treatment increased, microorganism counts decreased to $0.5{\times}10^2/ml$ and were not found above $135^{\circ}C$ - coliforms and psychrotrophic bacteria from $100^{\circ}C$ thermoduric bacteria, thermophiles, mould and yeast from $125-130^{\circ}C$. Heat treatment above $135^{\circ}C$ showed 100% sterilization effect. 4. The result of preservation test for heat treated milk did not show any significant changes in titratable acidity and general composition at $4^{\circ}C$, $25^{\circ}C$ and $37^{\circ}C$ up to 15 days. Viable bacteria counts, coliforms and psychrotrophic bacteria were not found but loss of vitamin and increase in viable bacteria counts appeared after 20 days.