Microplasma pretreatment of mango fruits during freeze drying with thermoelectric emission

Abstract

Introduction. The research objective was to study the effect of filamentous microplasma pretreatment on the efficiency of freeze drying. It featured mango fruit and assessed the quality of the dried product. Year-round availability of exotic fruit poses a challenge of providing consumers with high-quality food products. Freeze-drying, if combined with advanced electrophysical technologies, makes it possible to maintain the high quality of the product while improving the processing. This non-thermal method technology presupposes pretreatment with filamentous microplasma (FM) and thermoelectric emission. FM affects the membrane of plant cells and forms a through channel, thus improving mass transfer. Study objects and methods. Before freeze-drying, fresh mango fruit was cut into slices of 6.0 ± 0.5 mm each and the average diameter of 72 ± 3 mm. Freeze-dried fruits were analyzed according to the degree of rehydration and quality. FM treatment was performed at the electric field strength E = 600 kV/m, while the specific energy was 1 kJ/kg per unit. Results and discussion. FM pretreatment with thermoelectric emission reduced the drying time by 38%, which was enough to achieve equilibrium moisture content. It also increased the degree of rehydration from 2.58 to 3.14. FM pretreatment raised the total content of phenols and carotenoids, but reduced the total content of flavonoids. FM pretreatment also affected the antioxidant capacity, reducing it from 0.43 to 0.41 by the ABTS method and from 0.90 to 0.75 by the DPPH method. Conclusion. FM pretreatment increased the ability to restore the freeze-dried samples. The mango samples preserved the high content of phenols and carotenoids. The antioxidant capacity of the FM-treated samples proved to be slightly lower than in the control samples. In general, pretreatment with filamentous microplasma and thermoelectric emission had a positive effect on the quality of freeze-dried mango, reduced the processing time, and improved the rehydration characteristics of the final product.