Optimisation of processing variables affecting the osmotic dehydration of pomegranate arils

Combined Hot Air and Microwave-Vacuum Drying of Cranberries: Effects of Pretreatments and Pulsed Vacuum Osmotic Dehydration on Drying Kinetics and Physicochemical Properties

The aim of the study was to evaluate the effect of sonication (S), microwave-vacuum (MWV), convective freezing (F), cryogenic freezing (N), and their combinations, as well as pulsed vacuum osmotic dehydration (PVOD) on the drying kinetics, bioactive compounds, texture and color of whole cranberries during combined hot air convective drying, and microwave-vacuum drying (HACD+MWVD). Drying of berries took from 20 to 493 min. Drying rate was enhanced by 23% and drying time of non-osmotically dehydrated fruits was shortened by 33% using F treatment, while MWV decreased moisture content before drying by 68% and shortened the drying time of PVOD berries by 96%. Generally, total phenolic (TP) content increased during processing, total flavonoids (TF), and total monomeric anthocyanins (TMA) contents decreased, while the values of ferric reducing antioxidant power (FRAP) of dried fruits depended on the initial pretreatment. F and HACD+MWVD yielded fruits of the highest L* (33.8 ± 0.7), a* (25.2 ± 1.0), and b* (7.3 ± 0.6), inflated oval shape, and a small amount of wrinkles on the surface. PVOD and HACD+MWVD resulted in flat and wrinkled fruits.

Influence of osmotic dehydration pre-treatment and combined drying method on physico-chemical and sensory properties of pomegranate arils, cultivar Mollar de Elche

"Mollar de Elche" is the most popular Spanish pomegranate cultivar (intense sweetness and easy-to-chew arils); however, arils have pale pink colour and flat sensory profile. "Mollar the Elche" arils first underwent an osmotic dehydration pre-treatment (OD) with concentrated juices: (i) chokeberry, (ii) apple, and/or (iii) pomegranate cultivar "Wonderful", to improve their antioxidant capacity, colour, and sensory profile complexity, and later the arils were dried by a combined method (convective pre-drying+vacuum microwave finish drying). The use of OD provided dried arils with characteristic sweetness, and improved colour and aromatic complexity. The recommended OD methods were those using (i) pomegranate, and (ii) pomegranate with chokeberry juices; they improved the total anthocyanin content (mean of 368mgkg^-1), red colour (a^∗ coordinate 15.6), and antioxidant capacity (e.g. ABTS mean of 5.7mmolTrolox100g^-1). However, further research is still needed because freeze-dried arils had the highest anthocyanin content.

Optimization of osmotic dehydration conditions of peach slices in sucrose solution using response surface methodology

Osmotic dehydration (OD) conditions of peach slices were optimized using response surface methodology (RSM) with respect to sucrose concentration (50-70°B), immersion time (2-4 h) and process temperature (35-55 °C) for maximum water loss (WL), minimum solute gain (SG) and maximum rehydration ratio (RR) as response variables. A central composite rotatable design (CCRD) was used as experimental design. The models developed for all responses were significant. All model terms were significant in WL except the quadratic levels of sucrose concentration and temperature whereas in SG, linear terms of time and linear and quadratic terms of temperature were significant. All the terms except linear term of time and interaction term of time and sucrose concentration, were significant in RR. The optimized conditions were sucrose concentration = 69.9°B, time = 3.97 h and temperature = 37.63 °C in order to obtain WL of 28.42 (g/100 g of fresh weight), SG of 8.39 (g/100 g of fresh weight) and RR of 3.38.