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Fruit Ripening & Ethylene Management Page 98
Optimum Procedures for Ripening Tomatoes
by Marita Cantwell
Tomato Quality
The most important quality criteria for tomatoes are
red color, firm but juicy texture, and good flavor.
Good flavor depends principally on the amount of
sugars, acids and aroma volatiles. Different types of
tomatoes vary greatly in the content of sugars, acids
and other constituents (Table 1). Tomatoes with high
sugar and relatively high acid contents are the best
flavored, while low sugars and low acids result in
poor flavored tomatoes. The development of the
“jelly” in the locules of the fruit is important for good
tomato flavor since this locular tissue contains rela-
tively high concentrations of the sugars and acids.
Maturity and Ripeness Stages
Tomatoes may be harvested at various stages of ma-
turity and ripeness (Table 2). Tomatoes harvested
without any external red color are called mature-
green tomatoes, while those harvested at breaker or
more advanced stages are called vine-ripe tomatoes.
Since vine-ripe tomatoes may be less firm than ma-
ture-green fruit, extra care must be taken in their han-
dling to reduce bruising, compression and other
physical injuries. Table 3 describes typical color
changes for round tomatoes at different stages of ripe-
ness. Cultivars of round tomatoes for field produc-
tion can be harvested at mature-green stage and be
ripened into good quality tomatoes. However if fruit
are harvested without sufficient internal development
and are poorly handled, final ripe fruit quality will be
poor. For small tomatoes, harvesting at early color
stages (3) significantly reduces the sugar and soluble
solids contents in ripe fruit (Table 4).
Importance of Temperature on Ripening of Vine-
ripe fruits
For tomatoes with external color (vine-ripes), manag-
ing temperature will control the rate of ripening
(Table 5). Fruit with external color are already gener-
ating sufficient ethylene to complete the ripening
process. Temperatures that are both too low and too
high have serious consequences to tomato fruit qual-
ity. Superior quality tomatoes result if the fruits are
ripened at temperatures of 15-20°C (59-68°F). Rip-
ening fruits at temperatures above 25°C (77°F) results
in soft, poorly-colored fruits as high temperatures
inhibit ethylene production which is needed for good
lycopene synthesis (Figure 1). Breaker stage fruits
stored and ripened at temperatures of 15- 20°C (59-
68°F) have longer shelf-life, greater overall visual
quality, are firmer with less weight loss, have more
red color, and less decay than fruits ripened at higher
temperatures. Once fruits reach the red stage, an addi-
tional week of shelf life (with little change in firm-
Figure 1. The effect of temperature on the ripening physiol-
ogy of conventional round tomato (cv Mt. Fresh) fruit
(Cantwell, unpublished).
Respiration µL CO
2
.g
-1
h
-1
0
5
10
15
20
25
30
35
40
A. Respiration
Ethylene production nL.g
-1
h
-1
0
1
2
3
4
5
6
7
Days from Breaker Stage
-20246810
Color Score (1=green, 6=table-ripe)
1
2
3
4
5
6
B. Ethylene production
C. Color change
Mature-green Fruit
12.5°C (55°F)
20°C (68°F)
30°C (86°F)
Cantwell, M. 2010. Optimum Procedures for Ripening Tomatoes. In: Fruit Ripening and Ethylene Management, J.T. Thompson and C. Crisosto (eds.), UC
Postharvest Horticulture Series 9:106-116. http://postharvest.ucdavis.edu/files/93536.pdf.
Fruit Ripening & Ethylene Management Page 99
ness or flavor) can be expected if the fruits are held at
15-20°C (59-68°F) and are not physically damaged.
Unfortunately tomatoes are often stored at tempera-
tures below recommended and then ripened at tem-
peratures above optimum (Figure 2). This simply
leads to fruit with poor color and flavor.
Tomatoes are chilling sensitive and should not be
stored below 10°C (50°F) (Figure 2). Symptoms of
chilling injury on tomatoes may include decreased
flavor, lack of uniform ripening, and softness and
mealiness when transferred to warmer temperatures
for ripening. If tomatoes are stored long enough at
low temperature, there will be increased decay. Black
Alternaria decay on the stem end and shoulders is a
typical symptom of severe chilling injury. When
fruits are stored below the recommended 10°C (50°
F), volatile compounds that impart typical tomato
aroma and flavor are substantially reduced. This oc-
curs long before any visual symptoms of chilling oc-
cur. For example 4 days at 5°C (41°F) cause a signifi-
cant reduction in flavor quality, but about 6-8 days at
5°C (41°F) were neede to cause decay. Figure 3 il-
lustrates the impact of lower than recommended stor-
age temperature on the final red color and lycopene
content of round tomatoes. Storing tomatoes at 5°C
(41°F) for 1 week decreased the capacity of the fruit
to develop full red color when transferred to 20°C
(68°F) to complete ripening. Storage at 7.5°C (45°F)
for 2 weeks had a similar effect. The best option to
ensure final red color development is to store the fruit
not lower than the recommended temperature of 10°C
(50°F).
Ripening Mature-Green Fruit
Tomatoes with external color do not benefit from eth-
ylene treatment. Fruits with external color (stage 3)
are producing their own ethylene which is sufficient
to complete the ripening process. Mature-green fruits
also produce low amounts of ethylene and may even-
tually ripen. Generally though, mature-green fruit are
ethylene-treated to accelerate the ripening process.
Fruits respond better if ethylene treated soon after
harvest rather than after storage. It is generally rec-
ommended to use 100 ppm ethylene at 18-20°C (64-
68°F) with high humidity (>90%). Sufficient air flow
(about 0.1 to 0.2 cubic feet per minute per pound) to
maintain a uniform temperature profile through the
°F °C
32 0
35 2
40 4
45 7
50 10
55 12
60 16
65 18
70 21
75 24
80 27
85 29
90 32
Ripening
Range
MAX.
MIN. Recommended transit
& storage temperatures
Not more than
1-2 days
Recommended
Ripening Temp.
TOO COLD
Chilling injury
Poor color, flavor
Poor ripening,
softening
TOO WARM
Freezing point
31°F, -0.5°C
Figure 2. Tomatoes are chilling sensitive and
should not be stored below 10°C(50°F)
Hue color value
40
42
44
46
48
50
52
LSD.05
Weeks storage
0123
Lycopene, mg/kg FW
35
40
45
50
55
60
Red color, Hue
Lycopene
LSD.05
12.5°C (55°F)
10°C (50°F)
7.5°C (45°F)
5°C (41°F)
12.5°C (55°F)
10°C (50°F)
7.5°C (45°F)
5°C (41°F)
Figure 3. Red color values and lycopene concentra-
tions of tomatoes that were stored at 4 temperatures
and then ripened at 20°C (68°F). Fruit were color
stage 3 (30% color) when stored. The lower the hue
color value, the redder the fruit (Ara and Cantwell,
unpublished).
Fruit Ripening & Ethylene Management Page 100
room is important to ensure uniform ripening. Suffi-
cient ventilation is required to keep CO2 levels low
(<2%) or ripening will be slowed.
Tomatoes should respond within 3-3.5 days to ethyl-
ene treatment and reach breaker-turning stages of ripe-
ness. Fruits not showing external color change by that
time indicate fruits which were immature at harvest
and which should be discarded. Once ethylene has ini-
tiated ripening and external color change, the rate of
ripening can be managed at a range of temperatures as
shown in Table 4.
Poor flavor in tomatoes harvested as mature-green
fruit and ripened may be due to:
• harvesting immature fruit rather than well developed
mature-green fruit
• long delays from harvest to final ripening
• storing at lower than recommended temperatures and
then ripening
• mechanical damage which can lead to off-flavors.
Lack of uniform color in a tomato box
“Checkering-boarding” or lack of uniform coloration
is still a problem with mature-green ethylene treated
fruit and a high percentage of fruits require repacking.
Although this problem should not occur with vine-ripe
greenhouse tomatoes, it can happen if the packers are
not well trained or do not have sufficient time to dis-
tinguish between tomatoes with small differences in
external color. These small differences at the time of
packing will lead to greater heterogeneity during the
shipping and marketing period. Greenhouse fruit
should have a minimum of 20 or 30% external color to
ensure ripening uniformity in the box and to avoid
costly repacking.
Ripening Long Shelf-life Varieties
There are many varieties and experimental tomato
lines called long shelf-life (LSL) or extended shelf-life
(ESL) varieties which contain ripening mutant genes.
Figure 4 illustrates the effects of the rin mutant on
tomato ripening physiology. If these varieties are har-
vested too early in color development, they may not be
able to attain a final full red color. Lycopene synthesis
in tomatoes is linked to ethylene production capacity.
In such cultivars, harvesting fruit with more color en-
sures they are able to complete postharvest color de-
velopment. This is the case of many varieties grown
for greenhouse production and they need to be har-
vested with 30% or more color development. The rip-
ening physiology of both so called ‘conventional’ and
‘long-shelf life’ tomato cultivars may vary substan-
tially (Table 6).
Tomato ripening and 1-MCP (SmartFresh®)
SmartFresh® or 1–MCP is a very potent inhibitor of
ethylene action in fruits and can be used to manage
fruit ripening. An example of the impact of 1-MCP on
tomato ripening is described in Table 7. Fruit at four
color stages (3.5, 4, 4.5 and 5; see color chart of ripen-
ing) were treated with 500ppb 1-MCP and then held at
15, 20 or 25°C (59, 68 or 77°F) to complete ripening.
SmartFresh® treatment substantially extended the time
to ripen and the impact was greater at lower tempera-
ture. The final firmness of the 1-MCP treated fruit can
be less than the respective control fruit since total
weight loss during ripening can be higher due to the
longer period necessary. Final red color was good in
all cases, except for some fruit stored at 25°C in which
red color development, especially of early ripening
fruit, was inhibited at this temperature. In numerous
tests we found that composition of ripe tomatoes was
similar in untreated and the 1-MCP treated fruit.
µl CO
2
/g-h
0
5
10
15
20
25
30
Days at 20°C from Breaker stage
024681012141618
nl C
2
H
4
/g-h
0
1
2
3
4
5
6
7
8
9
Ethylene Production
Respiration
T3
T5
T3rin
T3rin x T5
Figure 4. The respiration and ethylene production
rates of tomato fruits of conventional parent (T3, T5),
mutant (T3rin) and hybrid (T3rin x T5) breeding
lines.
Fruit Ripening & Ethylene Management Page 101
References
Baldwin, E.A., K. Goodner, and A. Plotto. Interac-
tion of volatiles, sugars, and acids on perception of
tomato aroma and flavor descriptors. J. Food Sci. 73:
S294-S307.
Cantwell, M.I. and R.F. Kasmire. 2002. Postharvest
Handling Systems: Fruit Vegetables. In: Postharvest
Technology of Horticultural Crops (A.A. Kader, ed.).
University of California Pub.3311, pp. 407-421.
Cantwell, M., G. Hong and X. Nie. 2009. Impact of
storage conditions on grape tomato quality. Acta Hor-
ticulturae, in press, 8pp. (http://
postharvest.ucdavis.edu/datastorefiles/234-1531.pdf).
Collins, J.K. and P. Perkins-Veazie. 2006. Lycopene:
from plants to humans. HortScience 41: 1135-1144.
Hobson, G. and D. Grierson. 1993. Tomato. In:
G.Seymour, J. Taylor and G. Tucker (eds.), Biochem-
istry of Fruit Ripening. Chapman & Hall, London. pp.
405-442.
Kader, A.A. 1984. Effect of postharvest handling pro-
cedures on tomato quality. Acta Hort. 190: 221.
Mir, N., N. Canoles, R. Beaudry, E. Baldwin, C. Pal
Mehla. 2004. Inhibiting tomato ripening with 1-
methycyclopropene. J. Amer. Soc. Hort. Sci. 121(1):
112-120.
Simmonne, A.H., B.K. Behe, M. M. Marshall. 2006.
Consumers prefer low-priced and high-lycopene-
content fresh-market tomatoes. HortTechnology 16:
675-681.
Table 1. Examples of differences in composition of different types of ripe tomatoes purchased at
supermarkets in Davis, CA in April (Cantwell, unpublished).
Tomato type Fruit
weight
g
Red
color,
Hue
Soluble
solids,
%
Sugar,
mg/mL
Titratable
acidity,
%
Vitamin C
mg/100g
Lyco-
pene
mg/kg
Campari 53.1 44.2 6.3 31.4 0.58 40.5 63.0
Cherry 20.3 45.5 4.2 28.9 0.31 54.0 84.6
Grape 5.0 51.3 5.6 29.5 0.51 47.1 49.1
Grape 6.2 41.7 4.2 39.6 0.35 61.7 98.0
Orange Cluster 111.5 71.5 4.6 26.1 0.33 29.2 4.2
Round Cluster 102.1 43.2 7.6 20.1 0.62 26.9 53.6
Round Cluster 119.8 44.6 3.8 15.3 0.44 26.0 44.8
Round Greenhouse 231.2 45.9 4.5 22.5 0.36 30.4 28.0
Round Greenhouse 179.4 47.7 4.7 25.0 0.44 20.4 42.5
Roma 94.8 42.1 4.3 24.0 0.27 22.8 46.4
Roma 84.5 45.2 6.2 20.2 0.67 24.3 44.4
Romanita 20.5 41.3 6.3 32.9 0.44 45.9 70.3
LSD.05 6.7 2.4 0.3 5.0 0.08 8.0 7.5
Fruit Ripening & Ethylene Management Page 102
Table 2. Maturity and ripeness classes for fresh market tomatoes.
Class Name USDA no. Description
Immature -- Seeds cut by a sharp knife; no jellylike material in any of the lo-
cules; fruit is more than 10 days from breaker stage
Mature-green
Mature green 1 1 Seeds fully developed and not cut on slicing fruit; jellylike material
in at least one locule; fruit is 6 to 10 days from breaker
Mature green 2 1 Jellylike material well developed in locules but fruit still com-
pletely green; fruit is 2 to 5 days from breaker; minimum harvest
maturity
Mature green 3 1 Internal red color at the blossom end, but no external red color;
fruit is 1 to 2 days from breaker stage
Breaker 2 First external pink or yellow color at the blossom end
Turning 3 More than 10 percent but not more than 50 percent of the surface,
in the aggregate shows a definite change in color from green to
tannish-yellow, pink or red, or a combination thereof
Pink 4 More than 30 percent but not more than 60 percent of the surface,
in the aggregate, shows pink or red color
Light red 5 More than 60 percent of the surface, in the aggregate, shows pink-
ish-red or red, but less than 90 percent of the surface shows red
color
Red 6 More than 90 percent of the surface, in the aggregate, shows red
color
Full Red - Fruit has developed full final red color
Table 3. Typical changes in color values and lycopene concentrations during ripening of conventional round
tomato fruits.
L* indicates lightness (high value) to darkness; a* denotes changes from green to red. Chroma and hue values
indicate vividness and color, respectively. As a tomato ripens and gets redder, the hue value decreases. A to-
mato with a hue value around 40 indicates full red color.
Stage of Develop-
ment Ripening
stage L* a* b* Chroma Hue Lycopene
mg/kg FW
Mature-Green 1 62.7 -16.0 34.4 37.9 115.0 0.1
Breaker 2 55.8 -3.5 33.0 33.2 83.9 0.4
Pink-Orange 4 49.6 16.6 30.9 35.0 61.8 8.6
Orange-Red 5 46.2 24.3 27.0 36.3 48.0 16.8
Red; Table-ripe 6 41.9 26.4 23.1 35.1 41.3 30.7
Dark Red; overripe 6+ 39.6 27.5 20.7 34.4 37.0 36.9
Fruit Ripening & Ethylene Management Page 103
Table 4. Effect of maturity at harvest on quality and composition of ripe grape tomatoes. Data average of 7
cultivars (Cantwell, 2003).
Firmness is force to compress fruit 5mm.
Initial
color
stage
Fruit
weight, g Red color
Hue Firmness,
N Soluble
solids, % Sugars
mg/mL Titratable
acidity, % Vitamin C
mg/100m
L
3 4.9 36.8 11.5 5.9 27 0.59 96
4 5.7 36.3 13.6 6.7 30 0.68 97
5 5.9 37.7 13.7 7.5 33 0.67 99
LSD.05 0.6 ns 1.5 0.8 3 0.08 ns
Table 5. Effect of temperature on average ripening of conventional round tomato fruits at mature-green,
breaker, turning and pink stages.
Days to Full red color at indicated temperature
Color Stage 12.5
55 15
59 17.5
64 20
68 22.5
72 25°C
77°F
Mature-green 18 15 12 10 8 7
Breaker 16 13 10 8 6 5
Turning 13 10 8 6 4 3
Pink 10 8 6 4 3 2
Table 6. Ripening and quality characteristics of round tomatoes of conventional and long shelf-life varieties.
Physiology of fruits within a category may vary greatly. Tomatoes were harvested at the breaker-turning stage
and ripened at 20°C (68°F). Data are averages from 40 conventional varieties and 25 long shelf-life varieties
(Cantwell, unpublished).
Characteristic Conventional Varieties Long shelf-life Varieties
Ripening physiology Average Range Average Range
Days from Breaker to table-ripe 6.3 5.3-7.3 7.8 6.0-9.8
Maximum respiration rate (µL CO2/g-h) 20.9 16.4-27.5 19.3 14.9-26.7
Maximum ethylene production rate (nl/g-h) 4.8 2.3-9.4 2.4 1.5-7.8
Color when ripe (Hue) 38.5 34.7-44.2 43.3 38.0-48.2
Composition
% soluble solids 4.5 4.1-5.1 4.5 4.0-5.1
% titratable acidity 0.33 0.28-0.45 0.38 0.30-0.49
Fruit Ripening & Ethylene Management Page 104
Table 7. Fruit weight, weight loss, days to table-ripe, firmness and red color of tomato (cv. Bobcat)
ripened at 15, 20 and 25°C (58, 68 and 77°F). Fruit received no treatment or 1-MCP (500 ppb) treatment at the
color stages indicated. Data averages of 3 reps of 8 fruit (Cantwell, unpublished)
Treatment Temperature Initial
color stage Weight
loss, % Days to ta-
ble-ripe Firmness,
N Red color,
Hue
Control 15°C (59°F) 3.5 1.7 16.4 25.9 34.6
4 1.3 15.1 26.2 35.5
4.5 0.8 13.9 27.9 35.0
5 0.2 8.2 25.9 34.9
1-MCP 15°C (59°F) 3.5 2.6 28.0 21.2 38.2
4 2.3 25.8 21.7 37.7
4.5 1.8 19.3 20.4 36.9
5 1.0 11.1 22.1 37.5
Control 20°C (68°F) 3.5 1.4 10.1 27.1 35.5
4 1.0 8.3 26.3 36.4
4.5 0.9 6.1 24.0 35.2
5 0.4 4.0 27.1 35.6
1-MCP 20°C (68°F) 3.5 3.0 25.8 21.7 38.2
4 2.9 18.8 18.4 37.3
4.5 2.4 14.8 16.7 36.5
5 1.0 8.3 20.9 37.6
Control 25°C (77°F) 3.5 2.4 9.6 22.8 42.4
4 2.1 8.3 25.0 36.0
4.5 1.8 6.2 24.1 35.1
5 0.9 3.0 25.5 35.3
1-MCP 25°C (77°F) 3.5 4.5 17.0 22.5 43.6
4 4.1 15.0 22.3 39.0
4.5 2.3 10.1 25.4 39.8
5 1.6 4.7 21.8 37.4
Control Average 15°C 3.5 1.0 13.4 26.5 35.0
Average 20°C 4 1.0 7.1 26.1 35.7
Average 25°C 4.5 1.8 6.9 24.4 37.2
1-MCP Average 15°C 3.5 1.6 21.0 21.3 37.6
Average 20°C 4 2.3 17.7 19.4 37.4
Average 25°C 4.5 3.1 11.7 23.0 40.0
LSD.05 0.3 0.4 3.2 1.9
Fruit Ripening & Ethylene Management Page 105
Tomato Maturity & Ripening Stages
GREEN The tomato surface is completely green. The shade
of green may vary from light to dark.
BREAKERS There is a definite break of color from green to
tannish-yellow, pink or red of 10% or less of the tomato
surface.
TURNING Tannish-yellow, pink or red color shows on over
10% but not more than 30% of the tomato surface.
PINK Pink or red color shows on over 30% but not more
than 90% of the tomato surface.
LIGHT RED Pinkish-red or red color shows on over 60%
but red color covers not more than 90% of the tomato surface.
RED Red means that more than 90% of the tomato surface,
in aggregate, is red.
http://www.californiatomatofarmers.org
http://floridatomatoes.org
1
2
3
4
5
6
Fruit Ripening & Ethylene Management Page 106
Trevor V. Suslow and Marita Cantwell
Department of Plant Sciences, University of California, Davis, CA 95616
Maturity Indices Standard Tomatoes. Minimum harvest maturity (Mature Green 2) is defined by
internal fruit structure indices. Seeds are fully developed and are not cut upon slic-
ing 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 (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 mainly on external appearances, bruising & firmness.
- Greenhouse grown tomatoes are graded as U.S. No. 1 or No. 2 only.
Optimum Mature Green 12.5- 15°C (55- 60°F)
Temperature Light Red (USDA Color 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
Produce Facts
Tomato
Recommendations for Maintaining Postharvest Quality
Fruit Ripening & Ethylene Management Page 107
Optimum Mature-green tomatoes can be stored up to 14 days prior to ripening at 12.5°C
Temperature (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 reach-
ing 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 18-21°C (65-70ºF); 90-95% R.H. for standard ripening 14-16°C (57-61°F) for slow
Temperatures 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 in-
jury are failure to ripen and develop full color and flavor, irregular (blotchy) color de-
velopment, premature softening, surface pitting, browning of seeds, and increased de-
cay (especially Black mold caused by Alternaria spp.). Chilling injury is cumulative
and may be initiated in the field prior to harvest.
Optimum Relative 90-95%; High relative humidity is essential to maximize postharvest quality
Humidity and prevent water loss (desiccation). Extended periods of higher humidity or condensa-
tion may encourage the growth of stem-scar and surface molds.
Rates of Temperature 5°C (41°F) 10°C (50°F) 15°C (59°F) 20°C (68°F) 25°C (77°F)
Respiration ml CO2 / kg•hr
Mature-green 3-4NR 6-9 8-14 14-21 18-26
Ripening 7-8 12-15 12-22 15-26
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.
NR - not recommended for more than a few days due to chilling injury.
Ethylene 1.2 - 1.5µl/kg•hr at 10°C (50°F)
Production Rates 4.3 - 4.9µl/kg•hr at 20°C (68°F)
Responses to Tomatoes are sensitive to exogenous ethylene and exposure of mature-green
Ethylene 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.
Tomato
Fruit Ripening & Ethylene Management Page 108
Ripening 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.
Responses to Controlled atmosphere storage or shipping offers a moderate level of benefit.
Controlled Low O2 levels (3-5%) delay ripening and the development of surface and stem-
Atmospheres (CA) 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 main-
tain 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.
Physiological Freezing Injury. Freezing injury will be initiated at -1°C (30°F), depending on the
Disorders soluble solids content. Symptoms of freezing injury include a watersoaked appear-
ance, excessive softening, and desiccated appearance of the locular gel. (See Chill-
ing injury.)
Field Disorders Tomatoes are sensitive to many production and environment-genetic interaction
disorders which may be manifested during postharvest ripening or postharvest in-
spection. 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.
Reprinted from Horticultural Series #20, Produce Facts
Tomato POSTHARVEST TECHNOLOGY CENTER, UC Davis
http://postharvest.ucdavis.edu
