Development of an Apple Snack Enriched with Probiotic Lacticaseibacillus rhamnosus: 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 (RWTM) 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 RWTM 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, RWTM, and FD, respectively; the population in CD, RWTM remained while FD showed a decrease of one order of magnitude during storage. Comparing RWTM with FD, ∆E* was not significantly different (p < 0.05) and RWTM presented lower hardness values and higher crispness than FD, but the RWTM-dried apple slices had the highest TPC retention (41.3%). Microstructural analysis showed that RWTM produced a smoother surface, facilitating uniform moisture diffusion and lower mass transfer resistance. The effective moisture diffusion coefficient was higher in RWTM than in CD, resulting in shorter drying times. As a consequence, RWTM produced dried apple snacks enriched with probiotics, with color and TPC retention comparable to FD.

Application of CO2-Laser Micro-Perforation Technology to Freeze-Drying Whole Strawberry (Fragaria ananassa Duch.): Effect on Primary Drying Time and Fruit Quality.

Freeze-drying (FD) processing preserves foods by combining the most effective traditional technologies. FD conserves the structure, shape, freshness, nutritional/bioactive value, color, and aroma at levels similar to or better than those of refrigerated and frozen foods while delivering the shelf-stable convenience of canned/hot-air-dehydrated foods. The mass transfer rate is the essential factor that can slow down the FD process, resulting in an excessive primary drying time and high energy consumption. The objective of this study was to reduce the FD processing time using CO2 laser technology to improve product competitiveness in the preservation of whole strawberries. The research process consisted of the selection and characterization of fresh strawberries, followed by preparation, pre-treatment, freeze-drying, a primary drying time assessment, and a quality comparison. Experiments were carried out using strawberries without micro-perforation and with five and eight micro-perforations. Quality parameters were determined for fresh, frozen/thawed, and freeze-dried/rehydrated strawberries. It was found that the primary drying time can be significantly reduced by 20% (95% CI) from 26.7 h for non-perforated fruits to 22.3 h when five micro-perforations are made on each strawberry. The quality parameters used to evaluate the strawberries did not show significant differences when comparing frozen/thawed fruits with freeze-dried/rehydrated fruits. The experiments conducted in this study showed that freeze-drying may efficiently compete with freezing technology when processing whole strawberries.

Effect of CO2 Laser Microperforation Pretreatment on the Dehydration of Apple Slices during Refractive Window Drying.

This research studied the use of CO2 LASER microperforation as a pretreatment for the refractive window (RW) drying of apple slices with respect to total polyphenol content (TPC), antioxidant capacity, color ΔE, and product stability under accelerated storage. For this purpose, the processing variables assessed were pore size (200-600 µm), pore density (9-25 pores/cm2), and drying temperature (70-90 °C). As baseline criteria, a comparison with respect to the control without microperforations and samples subjected to conventional tunnel and lyophilization were also considered. The increase in the pore size from 200 to 600 µm resulted in shorter drying times (≤40 min), minimal change in color (ΔE) and loss of TPC, while DPPH was negatively affected by the combined effect of the pore density and the drying temperature. In general, the use of RW with CO2 resulted in apples of higher quality than those obtained in conventional drying and comparable to those obtained through the use of freeze-drying. Finally, during accelerated storage, quality attributes decreased significantly for samples dried at 90 °C regardless of whether microperforations were used, suggesting that a compromise between drying temperature and pore size must be weighed to reduce processing time and to avoid further quality losses during storage.