| Summary: | 碩士 === 東海大學 === 畜產與生物科技學系 === 102 === The fresh milk is the raw milk processed by heat treatment and is an important step before selling to the consumer, however, the level of thermal processing is not the same in different factories. Now, high temperature short time (HTST) pasteurization is been wide use, it has both the advantages of law destructive to nutrition and the good shelf life. Since there does not have a consistent agreement to the conditions of HTST pasteurization in our country, therefor, establishing a definite method as indicator to help distinguish heat intensity of fresh milk will be necessary. The purpose of this study is to discuss the changes of milk protein co-precipitate as affected by calcium chloride (CaCl2) concentrations, pH and ethanol concentrations as an indicator to distinguish various HTST pasteurization temperatures. Raw milk was obtained from Tunghai university experimental farm, there are five milk samples according to different heat treatment with 71, 76, 81, 86, and 91℃ for 15 sec. Adding 10 mM CaCl2 and adjusting pH into 6.0 with 10% ethanol before reheated-treatment (60℃, 30 min), the precipitate content in high-temperature (86 and 91℃) group is significantly higher than low (71 and 76℃) and mid temperature (81℃) group, and 91℃ is also significantly higher than 86℃. After adjusting pH to 5.8, the results showed that the precipitate content could differentiate low and mid temperature groups. In conclusion, milk protein co-precipitate as the pre-indicator to distinguish various HTST pasteurization temperatures could be possible, although between 71℃ and 76℃ still hard to do.
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