Development of an Apple Snack Enriched with Probiotic : Evaluation of the Refractance Window Drying Process on Cell Viability.

The objective of this study was to develop a dried apple snack enriched with probiotics, evaluate its viability using Refractance Window (RW) drying, and compare it with conventional hot air drying (CD) and freeze-drying (FD). Apple slices were impregnated with and dried at 45 °C using RW 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, and FD, respectively; the population in CD, RW remained while FD showed a decrease of one order of magnitude during storage. Comparing RW with FD, ∆E* was not significantly different ( < 0.05) and RWTM presented lower hardness values and higher crispness than FD, but the RW-dried apple slices had the highest TPC retention (41.3%). Microstructural analysis showed that RW produced a smoother surface, facilitating uniform moisture diffusion and lower mass transfer resistance. The effective moisture diffusion coefficient was higher in RW than in CD, resulting in shorter drying times. As a consequence, RW produced dried apple snacks enriched with probiotics, with color and TPC retention comparable to FD.