Abstract: Vacuum impregnation is a new technology of immobilization. It can incorporate lactic acid bacteria into apple tissues without destroying the initial food matrix. In this paper, three factors are optimized using response surface method. When the vacuum temperature was kept 35℃, air pump worked for ten minutes and the time of exposure in normal atmospheric pressure is 80 minutes, the total counts of Lactobacillus delbrueckii subsp.bulgaricus and Streptococcus thermophilus in apple pieces were around 109CFU/g. It can also be found that frozen drying is better than hot-air drying methods. It can keep the sensing qualities in good condition.

Key words: lactic acid bacteria, apple, vacuum impregnation, optimization