Orange

MATURITY & QUALITY

Maturity Indices

Soluble solids/acid ratio of 8 or higher and yellow-orange color at least on 25% of the fruit surface or soluble solids/acid ratio of 10 or higher and green-yellow color on 25% or greater of the fruit surface.

Quality Indices

• Color intensity and uniformity
• firmness
• size
• shape
• smoothness
• freedom from decay
• freedom from defects including physical damage (abrasions and bruising), skin blemishes and discoloration, freezing damage, chilling injury, and insect damage
• Flavor quality is related to soluble solids/acid ratio and absence of off-flavor-causing compounds including fermentative metabolites.

TEMPERATURE & CONTROLLED ATMOSPHERE (CA)

Optimum Temperature

3-8°C (38-46°F) for up to 3 months, depending on cultivar, maturity-ripeness stage at harvest and production area. Some Florida-grown cultivars can be kept at 0-1°C (32-34°F). Arizona-grown Valencia oranges should be kept at 9°C (48°F).

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

< 0.1 µl/kg·hr at 20°C (68°F)

Responses to Ethylene

Exposure to 1-10ppm ethylene for 1-3 days at 20-30°C (68-86°F) may be used for degreening oranges. This treatment does not influence the internal quality (including soluble solids/acid ratio) and may accelerate deterioration and decay incidence.

Responses to Controlled Atmospheres (CA)

A combination of 5-10% O₂ and 0-5% CO₂ can be useful for delaying senescence and for firmness retention but does not have a significant effect on decay incidence and severity, which is the limiting factor to long-term storage of oranges. Fungistatic levels (10-15%) of CO₂ are not used because they may result in off-flavors due to accumulation of fermentative metabolites. Commercial use of CA on oranges during storage and transport is very limited.