Microstructural, biochemical and drying characteristics of dehydrated 'Sunectwentyone' nectarines as affected by sodium metabisulphite

Impact of electrolyzed water as pre-treatments on drying properties and total colour difference of fresh-cut 'Tommy Atkins' mangoes

Mango fruits are a rich source of nutrients, however, due to their perishability and seasonality, minimal processing and drying offer the potential ensure a shelf stable and safe product. The use of sodium metabisulphite (SMB) as pre-treatment in the dried fruit industry has been widely adopted, but sulphite residue remains a health public concern. Therefore, this study investigated the effects of alkaline and acidic electrolyzed water (AIEW and AEW, mg/mL) as alternative pre-treatments to SMB (1% w/w) for 'Tommy Atkins' mango slices prior to hot air drying at 60 °C. Fresh-cut and untreated samples were used as a control. During the drying process the weight of the slices were monitored every 60 min for 10 h, which was used to calculate moisture ratio (MR), drying rate (DR), and the experimental data of the samples were subjected to eight thin layer models. Colour parameters (L*, a*, and b*) were measured, and use to determine colour intensity (C*), hue angle (h°), and total colour difference (TCD) before and after drying. Based on measured weight, continuous decline in MR was recorded for all dried mango slices over the drying time irrespective on treatment. Out of the eight applied thin layer models Henderson & Pabis and Logarithmic were the best appropriate models describing and predicting the drying behavior of 'Tommy Atkins' mangoes (R2 = 0.94, RMSE ≥ 0.0006). Samples treated with AEW treated samples had lowest L*, h°, and TCD values (p < 0.05). No significant different were found in h° values amongst all pre-treated and dried samples (p > 0.05), but these samples were significantly different from dried untreated (control) and fresh samples (p < 0.05). Pre-treatments maintained the visual quality of dried 'Tommy Atkins' mango slices; SMB > AIEW > AEW > untreated (control). This study provided science-based evidence for the application of acidic and alkaline electrolyzed water as an alternative pre-treatment to sodium metabisulphite for the drying of 'Tommy Atkins' mango.