Grapefruit
Maturity Indices
Color (more than 2/3 of fruit surface showing yellow color) and a minimum soluble solids/acid ratio of 5.5 or 6 (depending on production area). Grapefruit do not continue to ripen after harvest so they should be harvested fully-ripe (with good flavor).
Quality Indices
Color intensity and uniformity; firmness; size; shape; peel thickness; smoothness; and freedom from decay and defects, such as freezing injury, rind staining, pitting, scars, and insect damage. Flavor is related to soluble solids/acid ratio and concentration of compounds that impart bitter flavor (limonin and naringin).
Grapefruit Optimum Temperature
12-14°C (54-57°F) depending on cultivar, production area, maturity-ripeness stage at harvest, and storage & transport duration (up to 6-8 weeks).
Grapefruit Optimum Relative Humidity
90-95%
Rates of Respiration
Temperature | 10°C (50°F) | 13°C (55°F) | 15° (59°F) | 20° (68°F) |
ml CO2/ kg·hr | 3-5 | 4-7 | 5-9 | 7-12 |
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 20°C (68°F)
Responses to Ethylene
Exposure of mature-green grapefruits for 1-3 days to ethylene (1-10ppm) at 20-30°C (68 to 86°F) accelerates loss of green color and appearance of yellow color (degreening). This is accompanied by faster peel senescence and greater susceptibility to decay-causing pathogens.
Responses to Controlled Atmospheres (CA)
- Low O2(3-10%) and high CO2 (5-10%) concentrations delay senesence and maintain firmness of grapefruits kept at 13-15°C (55-59°C).
- Exposure to O2levels below 3% and/or CO2 levels above 10% may result in off- flavors due to accumulation of acetaldehyde, ethanol, and ethyl acetate. This precludes the use of fungistatic levels of CO2 (>10%) for longer than a few days.
- Commercial use of CA during transport and/or storage of grapefruits is very limited.