A study of the preharvest ripening of Hayward kiwifruit and how it is altered by N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU)
1992
De V. Lotter, J.
Fruit growth, total soluble solids (TSS), ethylene evolution, respiration rate, total titratable acids (TTA) and firmness were measured on fresh ‘Hayward’ kiwifruit during development. Measurements were made from two months after anthesis until one month after optimum harvesting date (OHD) as determined by TSS (7° Brix). The respiratory climacteric maximum varied from 14 days prior to OHD to seven days after OHD. Ethylene evolution remained below 0.5 μl 1-1 until the start of the climacteric, showing a pattern coincident with respiration climacteric. Both respiration rate and ethylene evolution showed a second increase after OHD. TSS continued to increase during the entire measuring period, and reached the OHD criterion of 7 ° Brix during the week ending 175 days after anthesis. There was a steady decline in firmness until OHD (6–7 kgf) and fruit softened rapidly thereafter. TTA increased to a maximum which coincided with OHD after which it declined rapidly. The application of CPPU at 10 ml 1-1 three weeks after anthesis, increased fruit size and advanced ripening by nearly one week, most notably a significant reduction in firmness and to a lesser extent, an increase in TSS. These results confirm that TSS and to a lesser extent, flesh firmness, are still the most suitable maturity indices for kiwifruit at present. Great care should be taken to harvest CPPU treated fruit at the correct OHD to ensure optimum quality.
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