Spray drying of skim milk was evaluated as a means of preserving Lactobacillus paracasei NFBC 338 and Lactobacillus salivarius UCC 118, which are human-derived strains with probiotic potential. Our initial experiments revealed that NFBC 338 is considerably more heat resistant in 20% (wt/vol) skim milk than UCC 118 is; the comparable decimal reduction times were 11.1 and 1.1 min, respectively, at 59°C. An air outlet temperature of 80 to 85°C was optimal for spray drying; these conditions resulted in powders with moisture contents of 4.1 to 4.2% and viable counts of 3.2 ؋ 10 9 CFU/g for NFBC 338 and 5.2 ؋ 10 7 CFU/g for UCC 118. Thus, L. paracasei NFBC 338 survived better than L. salivarius UCC 118 during spray drying; similar results were obtained when we used confocal scanning laser microscopy and LIVE/DEAD BacLight viability staining. In addition, confocal scanning laser microscopy revealed that the probiotic lactobacilli were located primarily in the powder particles. Although both spray-dried cultures appeared to be stressed, as shown by increased sensitivity to NaCl, bacteriocin production by UCC 118 was not affected by the process, nor was the activity of the bacteriocin peptide. The level of survival of NFBC 338 remained constant at ϳ1 ؋ 10 9 CFU/g during 2 months of powder storage at 4°C, while a decline in the level of survival of approximately 1 log (from 7.2 ؋ 10 7 to 9.5 ؋ 10 6 CFU/g) was observed for UCC 118 stored under the same conditions. However, survival of both Lactobacillus strains during powder storage was inversely related to the storage temperature. Our data demonstrate that spray drying may be a cost-effective way to produce large quantities of some probiotic cultures.Given that probiotic microorganisms play a role in promoting and maintaining health (29) has stimulated considerable interest in incorporating these into functional foods and pharmaceutical products. By definition, probiotics are "living microorganisms, which upon ingestion in certain numbers, exert health benefits beyond inherent basic nutrition" (13), and it is recommended that probiotic products contain at least 10 7 live microorganisms per g or per ml (15). Therefore, from a commercial point of view, an inexpensive method for large-scale production of cultures containing high levels of viable probiotic cells in a form suitable for product applications is highly desirable.In previous studies researchers have investigated the production of freeze-dried powders and frozen concentrates of probiotic Bifidobacterium and Lactobacillus spp. (10,12,24). However, there are many disadvantages associated with this approach; freeze-drying is time-consuming and expensive, there are high transport and storage costs associated with frozen concentrated cultures, and the freeze-thaw process is associated with a loss of culture viability. In comparison, spray drying, one of the predominant processing tools used in the dairy industry, can be used to produce large amounts of dairy ingredients relatively inexpensively; it has been estimated th...

(Gut 1999;44:156-162)

No abstract