RIPENING OF ATTACHED AND DETACHED SWEET PEPPER FRUIT CV. ‘DOMINO’

Capsicum fruit are classified as non-climacteric based on patterns of CO₂ and C₂H₄ production (Saltveit, 1977; Lu et al., 1990). However, some hot pepper cultivars are climacteric (Gross et al., 1986), indicating that classification of capsicum as non-climacteric may be inconclusive.
Different ripening patterns exist for attached and detached fruit (Saltveit, 1993; Shellie et al., 1993). Studies of the ripening behaviour of fruits is important to gain an understanding of the critical time when fruits will be responsive to postharvest ripening treatments.
This is especially relevant to sweet pepper which may require once-over harvesting for processing at the red ripe stage.
Such harvesting practice however, needs uniform ripening of fruits which may be induced by either ethylene or ethephon treatments.
Our objective in this study was to characterize the ripening behaviour of attached and detached sweet pepper fruit.

Sweet pepper plants, cv. ‘Domino’, were grown in the greenhouse using Nutrient Film Technique.
Forty fruit (1 per plant, 8 weeks from anthesis) were randomly selected for this experiment: 20 were left to ripen on the plant while the remaining 20 were removed and stored at 20°C to ripen.
Repeated internal gas samples were collected from a 1 cm hole, sealed with "Toray" rubber seal, made through the pedicel wall of the fruit using a sterile cork borer.
Skin colour change was measured using a Minolta Chromameter while internal CO₂ and C₂H₄ concentrations were analyzed using gas chromatography.

Colour change progressed from green to red in both attached and detached fruit during ripening.
In attached fruit, hue angle remained high for almost 7 days before declining rapidly from day 7 to 11. In contrast, detached fruit began to initially change colour sooner than attached fruit but changed more slowly from day 4 after harvest.
Colour intensity (chroma) increased in both attached and detached fruit as hue angle decreased, indicating degradation of chlorophyll and synthesis and/or unmasking of carotenoids.
Internal concentration of ethylene [C₂H₄]¹ increased with ripening, but this was more pronounced in attached fruit.
The significant increase in [C₂H₄]¹ coincided with the rapid decline in hue angle which was more evident in attached fruit.
Internal CO₂ concentration of attached fruit increased during ripening while that of detached fruit showed a steady decline.

We conclude there was an association between [C₂H₄]ⁱ and colour change in attached and detached fruit indicating that ethylene may be involved in ripening of sweet pepper.
There is an indication that capsicum fruits cv. ‘Domino’ are climacteric with respect to their internal ethylene concentration during ripening.
Egress of CO₂ and C₂H₄ through the stem scars of detached fruit may explain the differences in internal CO₂ concentration and the magnitude of peak [C₂H₄]ⁱ in attached and detached fruit rather than any inherent difference in fruit maturity.

International Postharvest Science Conference Postharvest 96

T. Tadesse, M.A. Nichols, E.W. Hewett

https://doi.org/10.17660/ActaHortic.1998.464.95