Effect of osmotic dehydration on the freeze-drying and hot air-drying process of Andean papaya

Andean papaya (Carica pubescens) is a fruit of high nutritional and functional value; however, it has a rapid rate of respiration and ripening, which limits its shelf life. For this reason, the kinetics of the osmotic dehydration (OD) process and its influence on the freeze-drying and hot air-drying processes were evaluated in the present study. Six OD treatments were applied combining two temperatures (30 °C and 40 °C) and three concentrations of sucrose solution (40, 50 and 60 °Brix). Moisture loss curves were analyzed and adjusted to mathematical models to describe the drying kinetics. T6 (40 °C, 60 °Brix) presented the highest efficiency, achieving a moisture reduction of 48.51%. This treatment was selected for subsequent processing by freeze-drying and hot air drying, thus obtaining four types of Andean papaya slice samples: hot air dried (CD), hot air dried with osmotic dehydration as pretreatment (CD-OD), freeze dried (FD), and freeze dried with osmotic dehydration as pretreatment (FD-OD). The FD-OD sample showed moisture values of 8.95% ± 0.68, water activity (aw) 0.56 ± 0.03, density 1.41 ± 0.03 g/cm3, and vitamin C of 3.27 mg/100 g dry basis. Concerning color, a lightness 73.91 ± 5.19, a* value (-5.08 ± 1.11) and b* value (70.7 ± 3.75), similar to those of fresh fruit, were obtained. The textural profile showed a softer and more elastic texture than the fresh sample, with values of hardness 29.05 N, chewiness 3.49 N, gumminess 5.79 N and elasticity (0.61 mm); however, cohesiveness (0.02) was comparable to the control sample. The results confirmed that OD as a pretreatment improved the quality of the final product and represents an effective alternative to prolong the shelf life of Andean papaya.