Recommendations for Maintaining Post-Harvest Quality

Reference: Carlos H Crisosto, Elizabeth J Mitcham, Adel A Kader
Department of Pomology, University of California, Davis, CA 95616

Maturity Indices
Green Olives: Size and colour – even pale green with a minimum of whitish spots (lenticels) through a straw colour. An olive is considered mature if it exudes a characteristic white juice when squeezed.
Black Olives: Colour, removal force, fruits when this stage about 3-4 months after the green stage.

Quality Indices
Green Olives: Colour, freedom from mechanical damage, shrivelling, surface blemishes, scale and other insect injury, and decay. These olives are processed according to the California black-ripe style or Spanish green style canned olives.
Black Olives: Colour, freedom from defects, oil content (12 to 25% depending on cultivar). These are processed (Greek or Italian style) or used for oil extraction.

Optimum Temperature
5 – 7.5oC (41 – 45.5oF), temperatures below 5oC (41oF) cause chilling injury of fresh olives.

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
Less than 0.1 (green olives) or 0.5 (black olives)  plethylene/kg.hr at 20°C (68°F)

Responses to Ethylene 
Olives produce very little ethylene but are moderately sensitive to ethylene action above 1 pm (loss of green colour and flesh firmness).

Responses to Controlled Atmospheres (CA)
Optimum CA 2 - 3% O2 + 0 – 1% CO2; delays senescence and softening for up to 12 weeks at 5oC (41oF) or 9 weeks at 7.5oC (45.5oF).
O2 below 2% can cause off-flavours.
CO2 greater than 5% may increase the severity of chilling injury if olives are kept below 7.5oC (45.5oF).
Note: The above information is for fresh green olives; fresh black olives should be processed as soon after harvest as possible.

Physiological Disorders
Chilling Injury (CI): can be a major cause of deterioration if fresh olives are stored before processing for longer than 2 weeks at 0oC (32°F), 5 weeks at 2°C (36oF), or 6 weeks at 3°C (38°F). Symptoms include internal browning that begins in the flesh around the pit and radiates outward toward the skin as time progresses. Skin browning indicates an advanced state and /or greater CI severity. The order of cultivar susceptibility to CI is Sevillano (most susceptible) – Ascolano – Manzanillo – Mission (least susceptible).
Nailhead: This disorder is characterised by surface pitting and spotting. It results from the death and collapse of epidermal cells, which create air pockets underneath the fruit skin. Symptoms are observed on olives kept at 10°C (50°F) for 6 weeks or longer or 7.5°C (45.5°F) for 12 weeks or longer.
Carbon Dioxide Injury: Symptoms (internal browning and increased decay incidence and severity), result from exposure to more than 5% CO2 for longer than 4 weeks.

Pathological Disorders
Post-harvest diseases occur if the olives have been chilled (exposed to temperatures below 5oC (41°F), mechanically damaged, not cooled promptly to the optimum temperature range of 5 - 7.5°C (41 - 45.5°F), or exposed to undesirable atmospheres (above 5% CO2 and/or below 2% O2).

Summary Table

Refrigerated Container / Coolroom Recommendations 

Key Properties

Other Properties

Controlled Atmosphere, Respiration

Seasonable Availability