益生菌乳粉贮存过程中水分、水分活度及活菌数变化的研究

Change of Moisture Content,Water Activity and Viable Cells of Probiotic Milk Powder during Storage

将益生菌乳粉贮藏于常温、42℃及50℃条件下,分别于不同贮存时间点测定乳粉的水分、水分活度(AW)和双歧杆菌活菌数,以分析乳粉贮存过程中各指标的变化趋势。结果显示:水分在42℃及50℃贮存过程中逐渐下降,但常温贮存乳粉的水分在贮存前期增高,后期降低;AW在贮存过程中表现为贮存前期升高,中期降低,后期再升高的趋势,且贮存末期AW显著高于起始值,但低于0.2。双歧杆菌在贮存过程中随着贮存时间的延长而逐渐下降,至贮存末期,常温和42℃贮存的乳粉其双歧杆菌活菌数大于1×107 CFU·g^(-1)。结果表明,在贮存过程中益生菌乳粉的AW会有较大的波动,较低的AW有利于益生菌在乳粉内的存活。

Moisture content, water activity（AW） and viable cells of Bifidobacterium were detected under the room temperature, 42 ℃ and 50 ℃ to analyze these indexes＇ changing during the storage of milk powder. Moisture content decreased steadily under 42 ℃ and 50 ℃ condition, while it firstly rose and then decreased under the room temperature during the storage. AW also increased firstly and then decreased, but it changed to go up in later stage. The final value of AW was higher than the initial value with lower than 0.2. Meanwhile, the viable cells of Bifidobacterium decreased with the time going on. At the end of test, the number of viable cells was more than 1×10^7 CFU·g^-1 under the room temperature and 42 ℃. AW showed greater fluctuation during the storage. And lower AW was benefit for the survival of probiotics in the milk powder.