Abstract
Abstract Kuini powders were obtained through spray-drying, freeze-drying, vacuum oven drying and convection oven drying. Colour, water activity (Aw), moisture content, hygroscopicity, wettability, flowability, degree of caking, water solubility index (WSI), total colour change, total phenolic content and total carotenoid content of Kuini powders were determined and compared. Convection oven drying resulted in the highest yield (46.97%), moisture content (4.91%), Aw (0.55) and WSI (74.33%) among all the drying methods. However, convection oven-dried Kuini powder had the lowest hygroscopicity and wettability, which were 18.66% and 12.04 s, respectively. Spray drying resulted in poor hygroscopicity (22.41%), degree of caking (22.16%), wettability (275s), WSI (45.67%) and higher colour change (59.81). Least total colour change (19.05) and higher yellowness (57.31) were observed in freeze-drying. In addition, freeze-dried Kuini powder had the highest total phenolic content (24.76 mg/100 g) and total carotenoid content (1.61 mg/100 g). Drying temperature had a negative and significant correlation with the retention of color pigments and antioxidant content. The physicochemical properties and antioxidant content of freeze-dried Kuini powder were preferred over spray-dried, vacuum oven-dried and convection oven-dried powders. Hence, freeze-drying offers potential application in the food products.
Highlights
Fresh fruits are highly perishable and have short shelf life
Heat is transferred from the surface to the interior of the material and moisture is removed through evaporation (Brennan & Grandison, 2006)
Each value in table represents the mean ± Standard Deviation (SD) with n=3. a-cMeans ± Standard Deviations (SD) followed by different superscript letters within the same column are significantly
Summary
Fresh fruits are highly perishable and have short shelf life. In order to make fruits available all year round, preservation is needed. Heat is transferred from the surface to the interior of the material and moisture is removed through evaporation (Brennan & Grandison, 2006). Whereas vacuum oven drying removes moisture under low pressure causes low shrinkage rate as well as colour degradation (Jaya & Das, 2003). Conversion of tropical fruit powder from puree and juice were reported for papaya, ‘Terung Asam’, and ‘Cempedak’ (Chang et al, 2020a, 2020b; Pui et al, 2020a, 2020b). Freeze-drying results in less damage to the initial properties of fruits as it includes crystallization and sublimation at reduced pressure (Caparino et al, 2012; Ceballos et al, 2012)
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