Effect of Chemical Pretreatment on Drying Kinetics and Physio-chemical Characteristics of Yellow European Plums

Abstract

Drying of plums to prunes is an important postharvest processing step, as it results in a product with higher nutrient density, increased shelf life, and significantly greater antioxidant and fiber content. However, due to the waxy layer present on the plums surface having low permeability toward moisture, plum dries very slowly which is an energy-demanding process. Therefore, to breakdown waxy layer on the surface and enhancement of skin moisture diffusivity, two genotypes (V91074 and V95141) of Yellow European Plums (YEPs) were dipped in 1% (w/ v) of Ascorbic Acid (AA), Citric Acid (CA), and Potassium Metabisulfite (KMS) solution for 1 min at 40°C. The pretreated YEPs were dried at three different temperatures (50°C, 60°C, and 70°C) until a final moisture content of approximately 30% (wet basis) was reached. It was observed that treated samples (AA and KMS) dried faster as compared to untreated samples, except for CA treatment where no significant difference in drying time was observed. One model cannot be selected for describing the thin layer drying characteristics of YEPs. Five out of 11 models used were found to be a perfect fit for genotype V91074 and genotype V95141, respectively. Pretreatment had a significant effect on effective moisture diffusivity (D eff ). D eff for untreated and treated plum samples ranged between 4.6 × 10 −11 to 8.6 × 10 −11 (m 2 /s) and 4.9 × 10 −11 to 9.1 × 10 −11 (m 2 /s). The drying temperature had a significant effect on phenolic content and antioxidant activity, whereas no significant effect of pretreatment was observed.

Convective Hot-air Drying of Green Mango: Influence of Hot Water Blanching and Chemical Pretreatments on Drying Kinetics and Physicochemical Properties of Dried Product

“…A reduction in drying time 10, 6.67, and 4.76% in each temperature interval also observed. Similar drying behavior for the influence of drying temperature on drying time has been reported for yellow European plums (Brar et al, 2020), cocoyam slices (Afolabi et al, 2015), and stone apple slices (Rayaguru and Routray, 2012). The present study results were in good agreement with the findings of Vardin and Yılmaz (2018), who reported that the moisture content of hot-water blanched pomegranate arils reached 16% (wb) in 168, 204 and 237 min at 75, 65, and 55°C, respectively.…”

“…Similarly, a decrease in ascorbic acid for treated and untreated Yellow European plums drying at higher temperature (70°C) has reported by Brar et al (2020). Besides, ascorbic acid pretreated plum samples showed a higher ascorbic acid content as compared to citric acid and potassium metabisulfite pretreatments.…”

“…The ascorbic acid content recorded in the range of 34.17-34.68 mg/100 g at 50°C, 32.31-33.19 mg/100 g at 60°C and 29.81-31.16 mg/100 g at 70°C. This decreasing trend may be due to the oxidation and heat-sensitive nature of ascorbic acid (Brar et al, 2020). Besides, pretreatments had a significant effect on changes in ascorbic acid content.…”

“…Deng et al (2019) reviewed that blanching increases the structure softening, cell wall destruction, and drying rate and reduces moisture movement resistance during drying. Brar et al (2020) stated that ascorbic acid is an enzyme inhibitor, bleaching and reducing agents. Udomkun et al (2014) reported that calcium is widely used to decrease physiological disorders, delaying membrane lipid catabolism, polyphenol oxidase induces browning, and improving firmness.…”

“…For hot water blanching, the sliced green mango samples were immersed in the water bath at 98°C for 3 min, and drained excess water and cooled immediately to prevent overcooking (Adepoju and Osunde, 2017;Dinrifo, 2012;Garba et al, 2015;Vardin and Yılmaz, 2018). For ascorbic acid pretreatment, 3% (w/v) ascorbic acid solution was prepared by dissolving 30 g ascorbic acid powder in 1000 mL distilled water, and the samples were immersed in the solution for 1 h at room temperature (approximately 30°C) (Adepoju and Osunde, 2017;Brar et al, 2020). For calcium chloride pretreatment, prepared a calcium chloride solution of 3% (w/v) by dissolving 30 g anhydrous calcium chloride in 1000 mL distilled water.…”