Avocado

MATURITY & QUALITY

Maturity Indices

Percent of dry matter is highly correlated with oil content and is used as a maturity index in California and most other avocado production areas; minimum dry matter required ranges from 19 to 25%, depending on cultivar (19.0% for ‘Fuerte’, 20.8% for ‘Hass’, and 24.2% for ‘Gwen’).

Florida-grown avocado cultivars have lower oil content and are harvested on the basis of a calendar date (days after full bloom).

Quality Indices

• Size (range of consumer preference)
• Shape (cultivar-dependent)
• Skin color
• Freedom from defects such as misshapen, sunburn, wounds and skin blemishes (rubs, insect damage, hail, and wind scars), rancidity and flesh browning
• Freedom from disease, including anthracnose and stem-end rot.
• Some cultivars are held on the tree for extended periods after achieving horticultural maturity.
• On-tree storage may result in development of off-flavors or rancidity with overmaturity.
• Off-flavors may also develop when fruit are harvested during periods of hot weather

TEMPERATURE & CONTROLLED ATMOSPHERE (CA)

Optimum Temperature

5-13°C (41-55°F) for mature-green avocados, depending on cultivar and duration. 2-4°C (36-40°F) for ripe avocados.

Optimum Relative Humidity

90-95%

Rates of Respiration

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

Avocado fruits do not ripen on the tree and ethylene production begins after harvest and increases greatly with ripening to > 100µl C₂H₄/kg·hr at 20°C (68°F).

Responses to Ethylene

Treatment with 100ppm ethylene at 20°C (68°F) for 48 hours (early-season fruits), 24 hours (mid-season fruits), or 12 hours (late-season fruits) induces avocados to ripen in 3-6 days, depending on cultivar and maturity. Ripening indices include flesh softening and change of skin color from green to black in some cultivars such as ‘Hass’. Ripe (soft) avocados require care in handling to minimize physical damage.

Responses to Controlled Atmospheres (CA)

• Optimum CA (2-5% O₂ and 3-10% CO₂) delay softening and skin color changes and reduce respiration and ethylene production rates.
• CA reduces chilling injury of avocado. Mature-green ‘Hass’ avocado can be kept at 5-7°C (41-45°F) in 2% O₂ and 3-5% CO₂ for 9 weeks, then ripened in air at 20°C (68°F) to good quality. Exclusion and/or removal of ethylene from CA storage are recommended.
• >10% CO₂ may increase skin and flesh discoloration and off-flavor development, especially when O₂is <1%.