Development of an Apple Snack Enriched with Probiotic Lacticaseibacillus rhamnosus: Evaluation of the Refractance...

The objective of this study was to develop a dried apple snack enriched with probiotics, evaluate its viability using Refractance Window (RW^TM) drying, and compare it with conventional hot air drying (CD) and freeze-drying (FD). Apple slices were impregnated with Lacticaseibacillus rhamnosus and dried at 45 °C using RW^TM and CD and FD. Total polyphenol content (TPC), color (∆E*), texture, and viable cell count were measured, and samples were stored for 28 days at 4 °C. Vacuum impregnation allowed for a probiotic inoculation of 8.53 log CFU/gdb. Retention values of 6.30, 6.67, and 7.20 log CFU/gdb were observed for CD, RW^TM, and FD, respectively; the population in CD, RW^TM remained while FD showed a decrease of one order of magnitude during storage. Comparing RW^TM with FD, ∆E* was not significantly different (p < 0.05) and RWTM presented lower hardness values and higher crispness than FD, but the RW^TM-dried apple slices had the highest TPC retention (41.3%). Microstructural analysis showed that RW^TM produced a smoother surface, facilitating uniform moisture diffusion and lower mass transfer resistance. The effective moisture diffusion coefficient was higher in RW^TM than in CD, resulting in shorter drying times. As a consequence, RW^TM produced dried apple snacks enriched with probiotics, with color and TPC retention comparable to FD.