Postharvest quality and physiological responses of clove bud extract dip on ‘Newhall’ navel orange

The ‘Newhall’ navel orange (Citrus sinensis L., Osbeck), a fruit of high nutritional value, is cultivated worldwide for both fresh and processed products. To fulfill consumers’ demand of less use of chemicals on fruit, more attention is now being paid to the search of natural compounds as alternative antimicrobials and preservatives. The effects of clove and their 95% ethanol extracts, a commonly used traditional Chinese medicine and spice, on the decay and quality as well as related physiological responses of navel oranges during postharvest storage were investigated. After harvest, navel oranges were immersed in 100 mg/mL clove extract (CE) for about 3 min and then the samples were stored at 7 °C and 90–95% RH. The results showed that the CE treatment significantly reduced the fruit's decay rate and weight loss compared with those of the control group. Meanwhile, total soluble solids content (TSS), titratable acidity (TA) and ascorbic acid (AsA) contents deterioration were substantially lower in the CE-treated group than those of the control group. Moreover, the activities of superoxide (SOD), peroxidase (POD) and chitinase (CHI) are effectively enhanced by the CE treatment, while no difference in β-1,3-glucanase activity was found between the two groups. This study suggests that CE might be a viable alternative to synthetic fungicides to extend the postharvest storage period and maintain fruits quality of navel orange.