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

Abstract

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.

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

“…The fresh apple slices had L* = 73.09 ± 1.44, a* = −6.48 ± 0.25 and b* = 22.14 ± 0.82, similar to the findings of [ 17 , 30 ]; on the other hand, the impregnated apple slices had L* = 69.92 ± 1.22, a* = −5.69 ± 0.32 and b* = 23.64 ± 1.08, with no differences observed between the impregnated and fresh samples ( p ≥ 0.05). Therefore, the impregnation solution did not significantly affect the color, as was also shown by [ 82 ] with L. rhamnosus cultures added to peach jam.…”

“…In this regard, the Refractance Window (RW TM ) is a fourth-generation drying technology that has gained much attention in recent years due to its several advantages [ 28 , 29 ]. The products, either in the form of pulp, puree, paste, or sliced, are spread over a flexible polyester film (e.g., Mylar), which is placed above hot water, and the drying process occurs by means of conduction and radiation [ 30 ]. This is an efficient drying technology with a higher drying rate and shorter drying time than other drying methods.…”

“…This is an efficient drying technology with a higher drying rate and shorter drying time than other drying methods. Compared with hot air drying, this new technology has a positive impact on the retention of bioactive compounds [ 28 ], as demonstrated by the drying of apples [ 30 , 31 ], carrots [ 32 ], tomato paste [ 33 ], cherry pulp [ 34 ], mangoes [ 35 ], blueberries [ 26 ], and kiwis [ 36 ], resulting in products obtained with greater retention of nutrients and reduced drying time. However, it is worth pointing out some disadvantages of RW TM , such as low production capacity and requiring the cleaning of the belt before or after a new process.…”

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

“…934.06. An amount of 5 to 10 g of the sample was dried under vacuum conditions in an oven at 70 • C for 24 h. The moisture of the sample was determined using Equation (1) [28]:…”

“…With this device, the coordinates of the uniform color space CIEL*a*b* were measured. The type of illuminant was D65, and the observer degree was 2 • [28]. The measurements were carried out in triplicate, obtaining the average of five measurements in the equatorial plane per strawberry.…”