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Recommendations for Maintaining Postharvest Quality


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

Temperature °C Temperature  °F  ml CO2/ kg·hr 
0 32 15-24
5 41 27-38
10 50 34-59
15 59 89-101
20 68 123-180

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 O may promote off-flavors and off-odors. Other studies report that 5 to 7% CO2extends 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.


Postharvest Technology Research and Information Center
Department of Pomology
University of California
One Shields Ave., Davis, CA 95616-8683

Send comments and questions to Postharvest Technology Research and Information Center
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Produce/ProduceFacts/Veg/peas.html updated July 10, 2000

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