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Pea
Snow and Snap Pod
Recommendations for Maintaining Postharvest Quality
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Trevor V. Suslow and Marita Cantwell
Department of Vegetable Crops, University of California, Davis, CA 95616
Introduction
Edible-Pod Peas include both Oriental or Asian (also Snow) flat type
pods, harvested when the seeds are very small and immature, and the Snap
or Sugar Snap Pea which resemble a typical fresh garden pea but with smaller
seeds.
Maturity Indices
Snow Peas are selected for size and maximal recovery of bright green,
flat pods with minimal seed enlargement. Older and yellowing pods are avoided
by careful hand-harvesting.
Sugar Snap Peas are selected in a similar manner but some degree of
seed-pod filling is desireable. Larger seeds rapidly become starchy.
Quality Indices
Edible-pod peas should be uniformly bright green (light to deep green
but not yellow-green), fully turgid, clean, and free from damage (Thrip
injury, broken pods). The stem and calyxes should be green and there should
be very few blossoms attached to the pods.
U.S. Grades : U.S. Fancy, and U.S. No. 1, (established in June 1942)
Standards for Fresh Peas apply to Snap Peas but not Oriental Peas
Optimum Temperature
0°C (32°F); 95-98% R.H.
Edible-pod peas are highly perishable and will not maintain good quality
for more than 2 weeks. Wilting, yellowing of pods, loss of tenderness,
development of starchiness and decay are likely to increase following storage
beyond 14 days; defects occur faster at common distribution conditions
of 5 to10°C(41 to 50°F).
Rates of Respiration
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Temperature °C
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Temperature °F
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ml CO2/ kg·hr
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0
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32
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15-24
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5
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41
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27-38
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10
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50
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34-59
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15
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59
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89-101
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20
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68
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123-180
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Respiration rates for edible-pod peas are an approximation
based on values for unshelled garden peas; actual values remain to be determined.
§ 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
< 0.1µl / kg·hr at 20°C (68°F)
Responses to Ethylene
Peas are moderately sensitive to exogenous ethylene. Accelerated yellowing
and decay will result from extended exposure to low levels of ethylene
during distribution and short-term storage. The calyx is more sensitive
to ethylene than the pod.
Responses to Controlled Atmosphere (CA)
Reports vary widely in the benefit of CA for Sugar and Snap Peas.
Atmospheres of 2 to 3% O2 and 2 to 3% CO2 are considered
by UC Research to offer the best , but moderate, benefit to peas
beyond that of rapid cooling and proper storage. Low O2
may promote off-flavors and off-odors. Other studies report that 5 to 7%
CO2 extends pod quality at 0°C.
Physiological Injury Disorders
Freezing. Freezing injury will be initiated at - 0.6°C
(30.9°F). Freezing injury results in watersoaking typically
followed by rapid decay by soft-rot bacteria.
Premature senescence. (yellowing of pod, browning of calyx, loss
of tenderness) will develop rapidly at temperatures 7.5°C(45°F)
due to the high rate of respiration.
Physical Injury
Harvesting and handling should be done with care to prevent damage to
the pods and attached calyx.
Pathological Disorders
A variety of fungal pod-spotting and decay pathogens affect edible-pod
peas. Common diseases include Chocolate Spot and Grey mold (Botrytis
cinerea), Watery Soft Rot (Sclerotinia sclerotiorum), Rhizopus
Rot, and Ascochyta Pod Spot. Bacterial Soft Rot is common following rough
handling or freezing injury. Surface decay can occur readily, on weak calyxes(brown
at harvest) and on blossom remains.
Special Considerations
Package-icing and top-icing loads may be used for Snow Peas but is typically
deterimental to Snap Peas because surface moisture promotes decay. Improper
CA/MA conditions in ready -to-cook vegetable medleys often leads to off-flavors
and fungal decay (typically Botrytis grey mold) at the blossom-end of the
pod.
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Produce/ProduceFacts/Veg/peas.html updated July 10, 2000
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