Effect of postharvest glucose infusion on exocarp colour of ‘Hass’ avocado (Persea americana Mill) during ripening

Purpose: The rejection of fruits because of insufficient purple colour in the exocarp has limited the profitability of ‘Hass’ avocado (Persea americana Mill) fruit. Thus, this study investigated whether glucose infusion through the pedicel can trigger anthocyanin pigment synthesis and accumulation of early harvested ‘Hass’ avocado exocarp, thereby resulting in improved colour development during ripening. Research method: ‘Hass’ fruit were continuously infused through the pedicel with distilled water and different glucose concentrations; ۰.۰۵, ۰.۱۳, ۰.۲۸ mM and control, therefore, assessed for fruit quality; firmness loss, visual colour) chromaticity parameters (lightness-L*, chroma-C* and hue-h°) and exocarp pigments (chlorophyll, carotenoids, anthocyanin and cyanidin-۳-O-glucoside) during ripening at ۲۵°C. Findings: Infusion of glucose and distilled water extended the ripening period by one day. Chlorophyll degradation was delayed in response to glucose infusions and distilled water compared to control. Results indicated that ۰.۰۵ and ۰.۱۳ mM glucose infusion increased anthocyanin and cyanidin-۳-O-glucoside accumulation in the exocarp, correspondingly improving exocarp colour (visual colour) after ۸ days at ۲۵°C when compared with ۰.۲۸ mM, distilled water and control. Limitations: Anthocyanin-regulating enzymes and genes of the ‘Hass’ avocado fruit have not yet been identified. Originality/Value: This study provides insight into the possible role of C۶ sugars in ‘Hass’ avocado fruit during postharvest ripening.By encouraging carbohydrate accumulation in the avocado fruit exocarp, postharvest poor exocarp colouration could be controlled.

Keywords:

anthocyanin , chlorophyll , Cyanidin-۳-O-glucoside , Persea americana Mill