Disaccharide incorporation to improve survival during storage of spray dried Lactobacillus rhamnosus in whey protein-maltodextrin carriers

The viability of encapsulated L. rhamnosus by spray drying, using carriers based on whey protein isolate-WPI and maltodextrins-MD, with and without sucrose or trehalose as protective agents, was studied as a function of the storage time and the equilibrium water activity (aw) at 20 °C. The water sorption and water plasticization behaviour of the dried products were also analysed. Although all the formulations were physically stable at aw below 0.43, the formulations stored at aw of 0.11 exhibited the best cell counts. No cell survival was observed after 84 days in WPI:MD formulations, but the partial replacement of maltodextrin by trehalose or sucrose allows for viable cells after 196 days. Cold storage of formulations enhanced cell preservation, although after 7 storage months only formulations containing disaccharide had viable cells. So, the incorporation of sucrose or trehalose to WPI:MD carriers is a good strategy to extend the shelf-life of L. rhamnosus probiotic products.