关键词: 益生菌, 喷雾干燥, 保护载体, 干燥历程, 单液滴干燥, 干燥动力学

Abstract: Gut microbiota exerts substantial influence on human health and thus attracts extensive research interests in recent years. Oral administration of living probiotics in adequate amount could alleviate inflammatory bowel disease,treat various types of diarrhea and promote digestion. Living probiotics in tablet form has been applied in clinical trials. In food industry,a relatively cost-effective and facile powder production approach is desired for manufacturing active probiotics product in order to reduce the cost and meet the need of the expanding market. Spray drying is a rapid powder production method with a high production capacity. However,during spray drying the atomized droplets will undergo a fast heating and dehydration process. The associated heat stress,dehydration stress,oxidative stress and other stresses will cause a substantial reduction of the viability of the probiotics in the droplets. Meanwhile,the structure of a spray dryer makes it difficult to track the drying process of each droplet. This issue represents a great challenge for studying the inactivation history of probiotics during drying and for exploring the interactions between carrier materials and probiotic cells. This article firstly discussed the droplet drying process inside a spray dryer,and then reviewed the changes in the probiotic viability as drying progresses,followed by a summary of common approaches to improve the viability of dried probiotics utilized in the literature. Three approaches were discussed,i.e.,improvement of the intrinsic stress tolerance of probiotic cells,optimization of the operation conditions of spray drying and incorporation of protective carrier. The interactions between carrier materials and probiotic cells and the influence of drying history are elucidated. This article shows that maximizing the viability of probiotics in spray dried powders requires a consolidated approach incorporating strategies from microbiology,process and food chemistry (material science). Development of high performance protectant formula based on understandings of microorganism-protectant interactions and designing novel production process from microbial culture to powder storage are key aspects to achieve high viability retention for mass production of active dry probiotics both in laboratory and in industries.

Key words: probiotics, spray drying, protective carrier, drying history, single droplet drying, drying kinetics