| Summary: | This research was aimed to reveal the effects of increasing CO, pressure level in carbonation process and storage duration as well as interaction of both on the change of pasteurized milk quality and consumer's preferences. The study involved such various stuffs as cow milk, sugar and CO,. A Completely Randomised Design in factorial 3 x 4 pattern was used in this study. The first factor was CO, pressure level (control, 4 psi, 8 psi and 12 psi), while the second one was the storage duration in refrigerator temperature (8-10°C) (0 day, third day, and sixth day). The fresh milk used in this study was the good quality. CO2level pressure gave effects (P < 0,01) on the pH value, acidity in the same level as lactic acid and total number of bacteria. The pressure also affected the consumer's preference (P< 0,05) in the nol day and had not any effect on protein, water, fat content, number of bacteria of Coliform, and consumer's preference in the sixth day of storage. The storage duration gave effect (P < 0,01) on pH value, acidity as high as lactic acid and the total number of bacteria. It also had effects (P< 0,05 ) on the number of bacteria of Coliform and consumer's preference on treated sample and control sample in CO, pressure as much as 4 psi. In contrast, it had not any effect on water, protein, fat content and consumer's preferences in treated sample with CO, pressure as much as 8 and 12 psi. In conclusion, CO, gas was able to maintain pasteurized milk quality for a six day -storage at refrigerator temperature (8-10°C) by pressing the rapid growth of total bacteria and Coliform bacteria without changing the general quality. The Consumer's preference level on pasteurized milk increased in favour of carbonation treatment. The highest level of consumer's was reached at level 8 psi. The interaction between the treatment of CO, pressure level and the storage duration was only on the pH value.
Keywords: carbonation � CO2pressure � storage duration � pasteurized milk � consumer preference
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