Strategies for the dehydration of Bifidobacterium animalis subsp. lactis INL1.

ZACARIAS, MF; AMBROS, S.; REINHEIMER, J.A.; VINDEROLA G.; KULOZIK, U.

Congreso; V Congreso Internacional de Ciencia y Tecnología de Alimentos (CICYTAC 2014).; 2014

Bifidobacterium animalis subsp. lactis INL1 (B.l. INL1) is a breast milk-derived potential probiotic. In the food industry, dehydrated cultures are preferred over frozen cultures due to their easiness of transport and storage. The aim of this study was to evaluate the effect of 5 different dehydration techniques on a superconcentrated culture of B.l. INL1 and to assess the survival under controlled storage conditions, in order to find the more suitable drying technology for this strain. The technologies applied were: spray drying (SD), freeze drying (FD), vacuum drying (VD), microwave vacuum drying (MWVD) and microwave freeze drying (MWFD). Different parameters (temperature, pressure, power input) were tested and the best conditions for each drying technique were chosen based on survival rate (SR %), residual water content (RWC %) and membrane integrity (MI %), and also considering the energetic efficiency of the process. Once the conditions were selected, a storage test was performed in order to compare the stability of the dried cultures. Two dryings of each dehydration technique were performed, with and without protectant (lactose). The dried products were stored at 25°C at two different water activities (aw=0.23 and aw=0.43) and SR, MI and RWC were determined immediately after drying and after 1, 2, 4, 6 and 8 weeks of storage. Among the 5 different drying processes tested, B.l. INL1 showed more tolerance to MWFD and FD (with and without protectant), followed by VD and MWVD. The most detrimental dehydration technique was SD when applied on the strain without protectant, but the SR and MI were highly increased in presence of lactose. Interestingly, when stored at 25ºC and aw=0.23, the FD and MWFD cultures were the most sensitive ones in the absence of lactose, being the VD culture the one with higher SR after 8 weeks. The protective effect of lactose during storage was evident in FD and MWFD cultures and SR was increased almost 10 times for both techniques. Moreover, at this storage condition, all dried cultures (with and without protectant) showed high viability (8.3-10.0 log CFU/g) after 8 weeks. When the dried cultures were kept at aw=0.43 (adverse condition) all cultures showed about 12.5% of RWC after 1 week and SR were lower than 2% after 1 week (without lactose) and 2 weeks (with lactose) for all dehydration techniques except for VD (SR= 9% after 2 weeks with lactose). B.l. INL1 showed high resistance to all drying techniques. In particular, MWFD was promising to obtain dried cultures in a short time, with low humidity and high viability. However, for adverse storage conditions, VD seems to be a good alternative. Lactose was an effective protectant for FD and MWFD but other agents should be tested for the other techniques.