关键词: 生牛乳, 冰点, 温度效应, 掺水检测, 掺假物质

Abstract: [Objective] By exploring the factors affecting the freezing point of raw milk,the effects of temperature changes,water content and dextrin and sodium chloride on freezing point detection results were analyzed to provide scientific basis for quality detection and adulteration determination of raw milk.[Method] By gradually increasing the temperature of the raw milk samples,the trend of freezing point changed with temperature was recorded. Water was added into raw milk according to volume ratio to determine the freezing under different water content. Dextrin and sodium chloride were added to quantitatively analyze the change of freezing point. Linear regression model was used to calculate the correlation between temperature,water content and adulterant addition and freezing point.[Result] It was found that the freezing point decreases by 0.001 0 ℃ for every 1 ℃ increase in average temperature. When the water content (volume ratio) was 1% and 2%,it was impossible to determine whether raw milk was watered. When the water content increased to 5% or more,it could be clearly judged as water addition on average,the freezing point value increased by 0.003 0 ℃ for each 1% water addition. The average freezing point decreased by 0.004 6 ℃ when the dextrin addition amount was 0.01~0.05 g/100 mL （calculated as an increase of 0.01 g/100 mL per dextrin addition）. The freezing point decreased by an average of 0.001 7 ℃ for every 0.01 g/100 mL increase of sodium chloride addition.[Conclusion] As the temperature of raw milk samples increased gradually,the freezing point showed a decreasing trend. With the increased of content,the freezing point increased correspondingly. The freezing point of raw milk decreased gradually when dextrin and sodium chloride were added，and the more the amount was added，the greater the freezing point decreased.

Key words: raw milk, freezing point, temperature effect, water addition detection, adulterant