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Aims: To optimize a spray coating process for the production of encapsulated microspheres containing viable Bi®dobacterium cells and to determine whether the readily gelatinized modi®ed starch coating used in this study improved bacterial survival in foods or under acid conditions. Methods and Results: An air inlet temperature of 100°C was demonstrated to be optimal for the spray drying process, as it afforded good drying, low outlet temperatures (45°C) and resulted in less than 1 log reduction in bi®dobacteria numbers during drying. Maximum recovery yields of 30% were obtained after optimizing the air aspiration conditions. The average size of the Bi®dobacterium PL1-containing starch microparticles was determined by scanning electron microscopy to be of the order of 5 lm. The starch-coated cells did not display any enhanced viability compared with free PL1 cells when exposed to acid conditions for 6 h or in two dry food preparations over 20 d storage at ambient temperature (19±24°C). Determination of 1491 nucleotides of the 16S rRNA gene from PL1 indicated that it shared 97% homology with a previously sequenced Bi®dobacterium ruminantium strain. Conclusions: Our data demonstrated that, although spray drying is a valuable process for encapsulating bi®dobacteria, further work is required to ascertain a more appropriate coating material that will protect this strain against adverse environmental conditions. Signi®cance and Impact of the Study: The production of small, uniformly coated microspheres containing viable bi®dobacteria using an affordable and industrially convenient process, such as spray drying, has commercial implications for the production of probiotic products. Although popular for use as a coating polymer by the food industry, this study indicated that modi®ed starches might not be suitable for use as an encapsulating material for probiotic strains.

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