ABSTRACT
Many factors can potentially impact the in vivo benefi cial properties of probiotics. In addition to host parameters such as microbiota, immunity, gastrointestinal transit and survival at the site of action, the viability and functional expression of probiotics are influenced by external factors, which include the preservation methods (e.g., freezing, freeze drying, and spray drying) and storage conditions. Probiotic cells can be maintained temporarily by chill storage usually for a day (Juárez Tomás et al. 2004) but may also last for a month at the most (Lee 2008). Frozen storage enables longer storage time of probiotics, and the lower the storage temperatures, the longer shelf life is. Only a small reduction in viability of cells occurs during storage at –70ºC to –80ºC for about one or two years (Foschino et al. 1996, Juárez Tomás et al. 2004), and commercial frozen concentrate of probiotic is generally recommended to be stored at a temperature lower than –45ºC in order to have a shelf life that lasts for at least 12 months (Bylund 2003). The refrigerated and frozen probiotics require a cold chain for storage and distribution, which is costly and inconvenient. Probiotic powder has advantages for industrial applications and long-distance trades. The dry powder is light, easy to handle, and has cheaper transportation costs. Moreover, in addition to using it as starter cultures for liquid and moist foods, probiotic powder can be added and mixed with dry or semi-dry foods such as cereal, chocolate, probiotic tablets and capsules. However, an important drawback of probiotic powder is the storage stability, which is often lower than frozen probiotics. Furthermore, for probiotics powder that is added as a functional ingredient in liquid and dry foods, and used in preparation forms, the stability is even more important because the number of viable cells depends largely on the initial cell concentration and storage stability since there is no fermentation or
Institute of Nutrition, Mahidol University, 999 Phutthamonthon 4 Rd., Salaya, Phutthamonthon, NakhonPathom 73170, Thailand.
