Direct Marketing and Quality Control
Adapted by Robert Kasmire, Vegetable Specialist, UC Davis Cooperative Extension, and Christie Wyman, Coordinator, Small Farm Center, UC Davis Cooperative Extension, from Florida Cooperative Extension publication "Vegetable Crop Fact Sheet" by Mark Sherman.
One reason consumers shop at farmers markets, fruit stands, and other direct marketing outlets is because they know the products are freshly picked and the quality of the produce is higher.
Poor postharvest handling practices can cause extensive loss of market quality, resulting in lower prices. Fresh produce is alive, and after harvest it depends upon its own food reserves for the energy needed to remain alive. We want to manipulate postharvest conditions so that product deterioration is minimized and the quality delivered to the consumer is maximized. We can do this by providing favorable:
- Harvest at optimum maturity for best eating quality. Immaturity increases water loss and shrivel. Some fruits (e.g., strawberries and tomatoes) may never ripen satisfactorily; others (melons, sweet corn) may be low in sugars. Overmature products such as beans, corn, and celery become tough. Overmature sweet corn will be low in sugars and starchy. Both immature and overmature produce are more susceptible to decay.
- Harvest during the coolest part of the day. This is most important for highly perishable products, because high temperatures lead to rapid deterioration. To minimize the spread of certain diseases, harvest should begin as soon as the foliage has dried.
- Harvest frequently for roadside marketing. Harvesting throughout the day to replace produce that has been sold will prevent quality deterioration between harvest and sale.
- Handle all produce gently. Cuts, punctures, abrasions, crushing, and bruising happen in every handling step. Fruits and vegetables may appear undamaged, but internal bruising may have occurred. Most decay and much of the water loss (shriveling) develops on fruits or vegetables where damage has occurred. You can reduce this by eliminating as many steps as possible between harvesting and marketing. The simplest and most effective way is to pack products directly into merchandizing containers. If this can't be done, pack products directly from field containers into merchandizing containers. Handle products carefully, and don't underpack or overpack your containers.
- Keep containers clean. Use water containing about 70 ppm chlorine (or one teaspoon of household bleach mixed with one gallon of water) to kill decay-causing organisms on the container surface and to remove sand or other trash that could injure the produce. (Plastic containers are easier to keep clean than wooden ones.)
- Keep harvested products out of the sun. This will minimize wilting, sunburn, and prevent unnecessary heating of produce. On a sunny, hot day, tomatoes held in the sun for one hour can be as much as 25°F hotter than fruit held in the shade.
- Avoid rough roads. Vibrations can cause considerable damage to produce. Grading field roads may be worthwhile. Tie or wedge the load securely to help reduce damage. Most small farm operators ship or haul their produce in nonrefrigerated trucks. If the weather is very hot or very cold, this can cause noticeable quality loss. Even refrigerated trucks can only maintain temperatures--they can't cool products during transit. If you have a refrigerated truck, keep the refrigeration units, doors, walls, and air delivery ducts in good operating condition to maintain adequate refrigeration.
- Don't overpack or underpack your containers. Packing too tightly causes compression bruises. If packed too loosely, the individual pieces vibrate against each other and sustain vibration bruises.
- Use new or sterilized containers. Residue from old produce can infect new produce.
- Make sure containers are not damaged. For instance, 80% of the stacking strength of fibreboard cartons is at the corners. If corners are damaged, much of the strength is lost. Carton strength is also reduced by bulge packing, wetting, and poor stacking in loads.
- Containers need adequate ventilation to permit cooling and temperature maintenance.
Strawberries, when covered with polyethylene film wrap and kept at 10°C, have 22 percent less dehydration and 33 percent less decay than those stored uncovered at 26.7°C after 3 days storage.
Temperature, water loss, and atmosphere composition
Temperature is the most important factor available for controlling product deterioration. Optimum temperatures increase shelflife and help maintain quality. (See Table 1) Temperatures that are too high increase water loss and encourage decay. Temperatures that are too low can cause chilling injury to sensitive products (decay, discoloration, pitting, and loss of flavor and ripening ability). If you do not have refrigeration you can help maintain the shelf-life of products by harvesting frequently, keeping them out of the sun, and stacking them so that they have sufficient air circulation.
Intermittent warming can be used to reduce or prevent chilling injury. Peaches can be stored for six weeks or more at 0°C if they are warmed for two days at 180°C after three weeks.
Water loss from fresh produce causes wilting in leafy vegetables and shriveling in fruits, tubers, and roots. Sprinkling or misting some vegetables (see Table 1) with fresh water, trimming tops from root crops and shanks from corn, and using protective plastic packaging will help reduce water loss.
|Crop||Relative Perishability1||Desirable Harvest Quality||Optimum Storage Conditions||Chilling Sensitive?2||Comments|
|Temp (°F)||Humidity (%)|
|1 Relative perishability under good storage conditions: L = Low, M = Moderate, H = High, VH = Very High.
2 Chilling sensitive crops should not be stored below their optimum temperature.
|Beans, Lima||M||Seeds developed and plump with tender green seed coats.||40-45||95||Yes||Sprinkle lightly.|
|Beans, pole & snap||H||Seeds immature; crisp pods free from blemishes||38-42||95+||Yes||Sprinkle lightly.|
|Beets||M||Roots firm, deep red, 1.5 to 3" diam.||32||98-100||No||Sprinkle lightly; remove tops.|
|Broccoli||VH||Green heads, flower buds developed but tight.||32||95+||No||Sprinkle lightly.|
|Brussels Sprouts||H||Firm sprouts, 1" diameter||32||95+||No||Sprinkle lightly.|
|Cabbage||M||Crisp, firm, compact heads.||32||95+||No||Sprinkle lightly.|
|Cantaloupes||M||Stem scar at maturity; skin yellowish tan; sweet, firm flesh with deep color.||38-41||95+||Yes|
|Carrots||M||Tender, crisp, sweet roots, deep orange.||32||95+||No||Sprinkle lightly; remove tops; ethylene exposure may cause bitterness.|
|Cauliflower||VH||Heads with compact, white curds.||32||95+||No||Sprinkle lightly.|
|Celery||VH||Stalks with crisp and tender petioles; no seed stalks.||32||95+||No||Sprinkle lightly.|
|Chard & Collards||H||Leaves fresh, green, young, and tender.||32||95+||No||Sprinkle lightly.|
|Corn, Sweet||VH||Kernels plump, sweet, milky, tender||32||95+||No||Sprinkle or top ice.|
|Cucumbers||H||Pickling: (1-4" long), crisp, green. Slicing: (6" long), crisp, green.||50-55||95+||Yes|
|Eggplants||H||Shiny, deep purple skin; seeds immature.||50-55||95+||Yes||Sprinkle lightly|
|Endive & Escarole||VH||Leaves fresh, crisp, and tender, free from discoloration.||32||95+||No||Sprinkle lightly.|
|Honeydew Melons||M||Surface waxy, white to creamy white in color; blossom-end springy under moderate pressure; characteristic aroma.||45-50||95+||Yes|
|Lettuce||VH||Heads compact and firm, fresh, crisp.||32||95+||No||Sprinkle lightly; ethylene exposure may cause russet spotting.|
|Mustard & Turnip Greens||H||Leaves tender and crisp; plants without flower stalks.||32||95+||No||Sprinkle lightly.|
|Onions, Dry||L||Firm bulbs, tight necks, dry leaf scales.||32||65-70||No|
|Onions, Green||VH||Crisp, green stalks with long white shanks.||32||95+||No||Sprinkle lightly.|
|Parsley||VH||Tender, crisp, green leaves.||32||95+||No||Sprinkle lightly.|
|Peas, English||VH||Seeds developed, but tender and sweet; pods still green.||32||95+||No||Sprinkle lighty.|
|Peas, Snow/Chinese||VH||Crisp, tender, green pods; seeds immature.||32||95+||No||Sprinkle lightly.|
|Peppers, Green||H||Crisp, firm, with shiny appearance.||50||95+||Yes|
|Potatoes, Irish||M||Well-shaped tubers free from sunburn and other defects.||55-70||90||Yes||If washed, dry thoroughly.|
|Potatoes, Sweet||L||Firm, smooth-skinned roots free from growth cracks and other injuries||55||90||Yes||All open surfaces should be well healed.|
|Pumpkins||L||Hard rinds, good color; heavy.||50-60||60||Yes|
|Radishes||M||Firm, crisp roots; red should be bright red, sizes up to 1.25" in diameter.||32||95+||No||Remove tops; sprinkle lightly.|
|Rutabagas||L||Firm roots with smooth surface.||32||95+||No||Sprinkle lightly.|
|Spinach||VH||Tender leaves, dark green, fresh, crisp||32||95+||No||Sprinkle lightly.|
|Squash, Yellow and Zucchini||H||Firm, shiny fruits, 4 to 6" long.||50||95+||Yes|
|Squash, Acorn||L||Fruits with hard, dark green skin with small, yellowish-orange areas.||50-60||60||Yes||Trim close, allow to heal.|
|Squash, Butternut||L||Fruits with hard, cream-colored skin.||50-60||60||Yes||Trim close, allow to heal.|
|Strawberries||VH||Berries firm, plump and red.||32||95+||No|
|Tomatoes, Green||H||Solid fruit with light green color, mature seeds, and locular jelly.||70||95+||Yes|
|Tomatoes, Ripe||VH||Solid fruits with uniform pink or red.||50-70||95+||Yes||Avoid storage below 50°F.|
|Turnips||M||Firm, heavy roots with good color.||32||95+||No||Remove tops; sprinkle lightly.|
|Watermelons, Whole||L||Mature with good flesh color; flesh sweet and crisp.||>55||80-90||Yes||Trim stems close to fruit and allow to heal.|
|Watermelons, Sliced||H||Mature with good flesh color; flesh sweet and crisp.||32||95+||---||Overwrap slices for protection.|
Though ethylene gas is helpful for ripening many commodities, it can also hasten unwanted ripening, cause loss of green in some immature products (cucumbers, squash, spap beans) and leafy vegetables, cause russet spotting on lettuce, bitterness in carrots, loss of leaves from cabbage, cauliflower and foliage ornamentals, and shorten the shelf-life of cut flowers. Many crops produce significant amounts of ethylene gas. Some of the more common ones include apples, avocados, peaches, pears, plums, cataloupes, honeydew melons, and tomatoes. Don't store ethylene sensitive and ethylene producing products in the same room. See Table 2 for storage ideas.
Display your products attractively. Remember that pyramid displays can result in the top fruit or vegetable rolling off and being damaged. In bins full of a products, the bottom layer can be injured. Consult tables 1 and 2 to be sure moisture and atmospheric needs of the products are being met.
Remove decaying products from displays and from the market area. When display bins are empty, disinfect surfaces with chlorinated water. Provide for routine removal of trash to a site remote from the market.
TABLE 2. Suggested Display and Storage Groups for Selected Vegetables.
|Crops within a group are compatible with respect to temperature, humidity, and ethylene sensitivity or production.|
|GROUP 1. Temperature = 32°, Relative Humidity = 90-95%, Ethylene Sensitive or Low Ethylene Producing.|
|Broccoli||Celery||Lettuce, All Types||Rutabagas|
|Brussels Sprouts||Swiss Chard||Mustard & Turnip Greens||Spinach, All Types|
|Chinese Cabbage||Sweet Corn||Parsley||Turnips|
|Carrots||Endive & Escarole||Peas, All Types||Sliced Watermelons|
|GROUP 2. Temperature = 32°, Relative Humidity = 65-70%, Low Ethylene Producing.|
|GROUP 3. Temperature = 50°, Relative Humidity = 90-95%, Chilling and Ethylene Sensitive Crops.|
|Beans, All Types||Eggplants||Peppers||Zucchini Squash|
|GROUP 4. Temperature = 50°, Relative Humidity = 90-95%, Chilling Sensitive Crops that Produce Ethylene.|
|Honeydew Melons||Muskmelons||Ripe Tomatoes|
|GROUP 5. Temperature = 70°, Relative Humidity = 60-80%, Crops that are Tolerant to Higher Temperatures.|
|Irish Potatoes||Sweet Potatoes||Mature Green Tomatoes||Watermelons|
|GROUP 6. Temperature = 70°, Relative Humidity = 60-80%, Crops Tolerant to Higher Temperatures and Lower Humidities.|
|Dry Onions||Pumpkins||Acorn & Butternut Squash||Watermelons|