Effect of vacuum on the impregnation of Lactobacillus rhamnosus microcapsules in apple slices using double emulsion

•L. rhamnosus was encapsulated within double emulsions.•OD and VOD process were used for the impregnation of probiotics into apple tissue.•Higher impregnation of probiotic was promoted by the solids gain and VOD process.

Mass transfer during the incorporation of probiotics protected within a double emulsion W1/O/W2 using hypertonic solutions were analyzed. Osmotic dehydration (OD) and vacuum osmotic dehydration (VOD) were used to impregnate the fruit with probiotics. Fresh apple tissue was soaked in osmotic solutions at 40, 50 and 60 °Brix, using a ratio of 1:9 (w/w) emulsion: sucrose solution. The results showed that the survival of probiotics decreased with increasing osmotic pressure of the solution. Higher impregnation of microorganisms was promoted by the application of a period (20 min) of vacuum treatment. Afterwards the atmospheric pressure was restore. The number of viable cells in the osmodehydrated apple was in the range 106-108 CFU/g d.b. Scanning electron microscope (SEM) images revealed the presence of microcapsules of 1-2 μm into apple tissue.