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Water activity in dry foods containing live probiotic bacteria should be carefully considered: A case study with Lactobacillus rhamnosus GG in flaxseed

Vesterlund, Satu, Salminen, Kari, Salminen, Seppo
International journal of food microbiology 2012 v.157 no.2 pp. 319-321
Lactobacillus rhamnosus, bacteria, case studies, food matrix, foods, linseed, new products, probiotics, shelf life, storage time, temperature, viability, water activity
This study evaluated the effect of water activity on the long-term storage stability of the probiotic Lactobacillus rhamnosus GG (LGG) in a dry food matrix. Viability of LGG was further studied in a crushed flaxseed matrix – a new possible product matrix to deliver probiotics – as well as in reference matrices as maltodextrin. Three different water activities (aw=0.11, 0.22 and 0.43) were used, and preparations were stored at room temperature for up to 14months. The viability of LGG was less dependent on the matrix used, but strongly dependent on the water activity. Viability in flaxseed was lost rapidly with aw 0.43: with aw 0.22 the reduction was 2.4 log₁₀ units and with aw 0.11 the reduction of viability was only 0.29 log₁₀ units during the entire storage time. Taken together, regulating water activity to a low value may offer possibilities for extending the shelf life of dry probiotic products.