Kiwifruit
Maturity Indices
- Kiwifruit Minimum of 6.5% soluble solids content (SSC) at harvest.
- Minimum flesh firmness of 14 lbf (penetration force with an 8-mm = 5/16 inch tip). Late harvested kiwifruits retain their firmness better than early harvested fruit and have higher SSC at harvest and when ripe.
Kiwifruit Quality Indices
- Freedom from growth cracks, insect injury, bruises, scars, sunscald, internal breakdown, and decay.
- Minimum of 14% SSC when ripe (ready to eat); a kiwifruit at 2-3 lb flesh firmness is considered ripe.
- Kiwifruits are a good source of vitamin C.
Kiwifruit Optimum Temperature
0°C (32°F); highest freezing point is -1.5°C (29.3°F).
Optimum Relative Humidity
90-95%
Rates of Respiration
Temperature | 0°C (32°F) | 5°C(41°F) | 10°C (50°F) | 15°C (59°F) | 20°C(68°F) |
Rates of Ethylene | 1.5-2.0 | 5-7 | 9-12 | 3-4 | 15-20 |
To calculate heat production multiply ml CO2/kg·hr by 440 to get Btu/ton/day or by 122 to get kcal/metric ton/day.
Rates of Ethylene Production
Less than 0.1 µl/kg·hr at 0°C (32°F), 0.1-0.5 µl/kg·hr at 20°C (68°F) for Production unripe kiwifruit. Ripe kiwifruit (less than 4 lbf firmness) produce 50-100 µl/kg·hr at 20°C (68°F)
Responses to Ethylene
- Kiwifruits are extremely sensitive to ethylene. As little as 5-10 ppb ethylene will induce fruit softening.
- Avoid exposure of unripe kiwifruits to ethylene during harvest, transport, and storage.
Responses to Controlled Atmospheres (CA)
Optimum CA 1-2% O2 + 3-5% CO2.
CA delays ripening and retains flesh firmness.
CO2 levels above 7% can cause internal breakdown of the flesh.
CA must be established within 2 days after harvest to maximize benefits; ethylene concentration should be kept below 20 ppb to avoid accelerated flesh softening and incidence of white core inclusions.