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Home > Recommendations > Produce Facts > Tomato
Tomato
Recommendations for Maintaining Postharvest Quality
Trevor V. Suslow and Marita Cantwell
Standard Tomatoes: Minimum harvest maturity (Mature Green 2) is defined by internal fruit structure indices. Seeds are fully developed and are not cut upon slicing the fruit. Gel formation is advanced in at least one locule and jellylike material is forming in other locules.
ESL* Tomatoes: Off-vine ripening is severely affected if fruit are harvested at the MG2 stage. Minimum harvest maturity is better defined as equivalent to ripeness class Pink (USDA Color Stage 4 more than 30 percent but no more than 60 percent of the fruit surface, overall, shows a pink-red color.)
* Extended Shelf-Life trait is due, in part, to either the presence of the rin or nor gene.
Quality Indices
Standard tomato quality is primarily based on uniform shape and freedom from growth or handling defects. Size is not a factor of grade quality but may strongly influence commercial quality expectations.
Shape - well formed for type (round, globe, flattened globe,
roma)
Color - Uniform color (orange-red to deep red; light yellow).
No green shoulders.
Appearance - Smooth and small blossom-end scar and stem-end
scar. Absence of growth cracks, catfacing, zippering, sunscald, insect
injury, and mechanical injury or bruises.
Firmness - Yields to firm hand pressure. Not soft and easily
deformed due to an overripe condition.
U.S. grades are No. 1, Combination, No. 2, and No. 3. Distinction
among grades is based predominantly on external appearances, bruising and
firmness.
Greenhouse grown tomatoes are graded as U.S. No. 1 or No. 2 only.
Optimum Temperature
Mature Green 12.5 - 15°C (55 - 60°F)
Light Red (USDAColor Stage 5) 10 - 12.5°C
(50 - 55°F)
Firm-ripe (USDA Color Stage 6) 7 - 10°C
(44 - 50°F) for 3-5 days
Mature-green tomatoes can be stored up to 14 days prior to ripening at 12.5°C (55°F) without significant reduction of sensory quality and color development. Decay is likely to increase following storage beyond two weeks, at this temperature. Typically 8-10 days of shelflife are attainable within the optimum temperature range after reaching the Firm-ripe stage. Short term storage or transit temperatures below this range are used by some in the trade but will result in chilling injury after several days. Extended storage with controlled atmosphere has been demonstrated. (See Responses to CA)
Ripening Temperatures
18° -21°C (65 - 70°F); 90-95% R.H.
for standard ripening 14° -16°C (57- 61°F)
for slow ripening (i.e. in transit).
For more details on ripening conditions see Ripening.
Chilling Injury
Tomatoes are chilling sensitive at temperatures below 10°C (50°F) if held for longer than 2 weeks or at 5°C (41°F) for longer than 6-8 days. Consequences of chilling injury are failure to ripen and develop full color and flavor, irregular (blotchy) color development, premature softening, surface pitting, browning of seeds, and increased decay (especially Black mold caused by Alternaria spp.). Chilling injury is cumulative and may be initiated in the field prior to harvest.
Optimum Relative Humidity
90-95%; High relative humidity is essential to maximize postharvest quality and prevent water loss (desiccation). Extended periods of higher humidity or condensation may encourage the growth of stem-scar and surface molds.
Rates of Respiration
| Temperature |
|
|
| 5°C (41°F) | ||
| 10°C (50°F) |
|
|
| 15°C (59°F) |
|
|
| 20°C (68°F) |
|
|
| 25°C (77°F) |
|
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.
1.2 - 1.5µl / kg·hr at 10°C (50°F)
Tomatoes are sensitive to exogenous ethylene and exposure of mature-green
fruit to ethylene will initiate ripening. Ripening tomatoes produce ethylene
at a moderate rate and co-storage or shipment with sensitive commodities,
such as lettuce and cucumbers, should be avoided.
Faster ripening results from higher temperatures between 12.5 -25°C
(55-77°F); 90-95% R.H.; 100 ppm ethylene. Good air circulation
must be maintained to ensure temperature uniformity within the ripening
room and to prevent the accumulation of CO2. CO2
(above 1%) retards the action of ethylene in stimulating ripening.
The optimum ripening temperature to ensure sensory and nutritive
quality is 20°C (68°F). Color development is optimal
and retention of vitamin C content is highest at this ripening temperature.
Tomatoes allowed to ripen off-the-vine above 25°C (77°F)
will develop a more yellow and less red color and will be softer.
Ethylene treatment typically extends for 24-72 hours. A second treatment
period may follow repacking if immature green fruit were included in the
harvest.
Controlled atmosphere storage or shipping offer a moderate level of
benefit. Low O2 levels (3-5%) delay ripening and the development
of surface and stem-scar molds without severely impacting sensory quality
for most consumers. Storage times of up to 7 weeks have been reported for
tomatoes using a combination of 4% O2, 2% CO2, and
5% CO. More typically, 3% O2 and 0-3% CO2 are used
to maintain acceptable quality for up to 6 weeks prior to ripening. Elevated
CO2 above 3-5 % is not tolerated by most cultivars and will cause
injury. Low O2( 1%) will cause off-flavors, objectionable odors,
and other condition defects, such as internal browning.
See Chilling injury.
Freezing Injury. Freezing injury will be initiated at -1°C
(30°F), depending on the soluble solids content. Symptoms of
freezing injury include a watersoaked appearance, excessive softening,
desiccated appearance of the locular gel.
Tomatoes are sensitive to many production and environment-genetic
interaction disorders which may Disorders be manifested during postharvest
ripening or postharvest inspection. Fertilizer and irrigation management,
weather conditions, insect feeding injury, asymptomatic virus infection,
and unknown agents may interact to affect postharvest quality. Examples
are Blossom-end Rot, Internal White Tissue, Rain Checking, Concentric and
Radial Cracking, Puffiness, Persistent Green Shoulder, and Graywall. Several
references with photographic keys to disorders are available.
Diseases are an important source of postharvest loss depending on season,
region and handling practices. Commonly, decay or surface lesions result
from the fungal pathogens Alternaria (Black Mold Rot), Botrytis (Gray Mold
Rot), Geotrichum (Sour Rot), and Rhizopus (Hairy Rot). Bacterial Soft Rot
caused by Erwinia spp. can be a serious problem particularly if proper
harvest and packinghouse sanitation is not used. Treatment with hot air
or hot water immersion (55°C for 0.5 - 1.0 min.) has been effective
in preventing surface mold but has not been used extensively for commercial
treatments. CA can be effective in delaying fungal growth on the stem-end
and fruit surface.
Greenhouse tomatoes marketed on-the-vine ("cluster tomatoes") are very
susceptible to Botrytis Gray Mold, especially if film-wrapped in a tray.
Rapid cooling soon after harvest is essential for optimal postharvest
keeping quality. The precooling endpoint is typically 12.5°C
(55°F). Forced-air cooling is the most effective practice but
room cooling is more common.
[For more information, see our publication “Management of Fruit Ripening”,
available for purchase using our Order Form.]
NR - not
recommended for more than a few days due to chilling injury
Rates of Ethylene Production
4.3 - 4.9µl / kg·hr at 20°C (68°F)
Responses to Ethylene
Ripening
Responses to Controlled Atmospheres (CA)
Physiological Disorders
Physical Disorders
Pathological Disorders
Special Considerations
Department of Plant Sciences
Mail Stop 2, Room 3047 Wickson Hall
University of California
One Shields Ave., Davis, CA 95616-8683
Send comments to postharvest@ucdavis.edu
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