Abstract
The purpose of this study was to investigate the effects of salicylic acid (SA) dips incorporated with ultra violet-C (UVC) irradiation on postharvest quality of longan fruit cv. ‘Dor’ during refrigerated storage at 10°C. The longan fruit were dipped in SA solution at the concentration of 0, 1.0, 2.0 and 3.0 mM before irradiated with 6.6 kJ m-2 UVC. Physicochemical quality attributes including peel colour, taste attributes, fruit decay, sensorial qualities and bioactive compounds were monitored. SA dips incorporated with the UVC irradiation maintained the outer peel lightness (L*), total ascorbic acid (TAA) content and crispness score of flesh as well as lowered colour difference (∆E*) value of outer peel and the reduction total antioxidant capacity (TAC) of the flesh during storage. All treatments did not affect the fruit taste attributes including total soluble solids (TSS), total acidity (TA) and TSS/TA ratio. The fruit dipped with 2.0 and 3.0 mM SA incorporated with the UVC irradiation effectively delayed the fruit decay as well as inhibited off-flavour. The fruit dipped with 2.0 mM SA incorporated with UVC irradiation showed the highest acceptability score and also enhanced the activity of antioxidant enzymes such as ascorbic acid peroxidase (APX), superoxide dismutase (SOD) and catalase (CAT).
Highlights
Longan (Dimocarpus longan Lour.) is known as a nonclimacteric subtropical fruit native to China, Southeast Asia and Northeastern India
salicylic acid (SA) dips incorporated with 6.6 kJ m-2 ultra violet-C (UVC) irradiation maintained the L* value and ∆E* value of the outer peel whilst a marked decrease in L* value and increase in ∆E* value were found in the outer fruit peel irradiated with 6.6 kJ m-2 UVC and the untreated fruit
A previous works of Promyou and Supapvanich (2012) who reported that UVC irradiation did not affect the change in L* value of ‘Golden’ bell pepper fruit and Supapvanich (2015) who found that the combination of SA and hot water dip lowered the rambutan fruit skin browning
Summary
Longan (Dimocarpus longan Lour.) is known as a nonclimacteric subtropical fruit native to China, Southeast Asia and Northeastern India. In Southeast Asia countries, longan is a commercially famous fruit and widely grown in Vietnam and north of Thailand (Nakason and Paull 1998; Whangchai et al, 2006). The rapid deterioration of the fruit after harvest involving pericarp browning, fruit rot and pulp breakdown is the main factor reducing its shelf-life and marketing value (Jiang et al, 2002; Duan et al, 2007). It is widely recognized that pericarp browning of longan fruit after harvest has mainly been attributed to oxidation of phenolic compounds and browning enzymes such as polyphenol oxidase, phenylalanine ammonia lyase and peroxidase (Jiang 1999; Duan et al, 2007; Cheng et al, 2009). The alternative methods replacing SO2 use have been recommended and widely investigated such as the use of ozone (Kim et al, 1999), X-ray irradiation (Follett and Sanxter, 2000), nitric oxide treatment (Duan et al, 2007) and hydrochloric acid dip (Apai, 2010)
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