Abstract: The paper dealed with the effects of (pH4~6.2) hydrogen chloride as well as different food acids on residual activity of L.debrueckii subsp .delbrueckii .The experiment showed that L.debrueckii subsp .Delbrueckii had the highest residual activity at 4~8℃. PH4. 0 in carrot juice for 21 days.The food acids such as acetic acid,citric acid and lactic acid with adjusted acidity of carrot juice (pH4 .0) all affected the activity of L.debrueckii subsp. delbrueckii, but acetic acid had the least effect on residual activity of L. debrueckii subsp. delbrueckii .Hydrogen chloride (pH2. 0 ~4. 0 ) showed activity effect of L. debrueckii subsp.delbrueckii, the large the acidity, the less the activity of L.debrueckii subsp.delbrueckii.

Key words: L.debrueckii subsp delbrueckii Residual activity Acid