Harvest & Postharvest
Harvest & Postharvest
Harvested fruits and nuts are living things—they use O2 and give off CO2 in respiration. Fruit should be harvested when it is ready to pick or mature. Harvesting at the time of optimum maturity will produce the best quality fruit. Harvesting when fruit is cool (early morning) and cooling the fruit as soon as possible promotes quality and shelf life.
Harvest most fruits by twisting and lifting the fruit up, not by pulling straight down from the spur or branch. Proper technique is important for minimizing bruises and injuries. Place fruits gently in your harvesting container. Do not just drop them in. Softer fruits require more careful handling to avoid bruises, but firmer fruits at harvest require more careful handling to avoid skin punctures.
- Mature: the stage that will ensure ripening after the fruit is harvested.
- Optimum maturity: that point of maturity when fruit has reached its best quality for harvest.
- Ripe: the point where fruit will start to deteriorate if not eaten.
Ripening differs among different types of fruits. In many species such as berries, stone fruits, nuts, figs, and grapes, ripening occurs prior to harvest. In others, such as pear, quince, late apples, persimmons, European pears, and avocados, ripening takes place largely or entirely after harvest—they must not be tree-ripened. Fruit softens after it is picked. Some pears may change ground or skin color.
Asian pears ripen best on the tree. Pick them when skin turns yellow or when they taste sweet (russeted types). Apples can be tree-ripened, but most are picked earlier and ripened. When left on the tree, they tend to drop badly before harvest and they can become mealy and of poor quality. After apples mature, the starch must change to sugar for optimum flavor. Citrus, berries, and persimmons undergo changes on skin and flesh color as well as taste.
Nuts should be harvested when they are ripe. Hazelnut (filbert) maturity occurs when filberts are shed from the husk in September, October, or November. When they drop, they are fully mature, but they must be “cured” and dried to 8–10% moisture content. Walnuts are mature 1–4 weeks before hull cracking. They can be dried to 3–4% moisture (on a kernel basis) immediately after harvest. Almonds are mature and ready for harvest when they are loose enough to be knocked and hulled. Mature pecans do not fall from the tree all at once. Pecans reach maturity when the husks open from around the nuts. Pistachios reach maturity when their skin changes from translucent to opaque and a loosening of the hull from the shell occurs. When the hull shrivels and separates easily from the shell, optimum maturity has been reached. Chestnuts mature over a period of weeks from September into November, depending on climate. When mature they fall easily from the tree and separate from the burr easily. Chestnuts are not like other nuts; for fresh eating, they should be stored like apples at 33°F and high relative humidity. They can also be peeled and dried for later rehydration or ground into chestnut flour.
There are many measures of maturity. Some require specialized instruments and are not always practical for the home orchardist. The following chart lists a variety of measures of maturity.
|Type of Test||Used For|
|Days from Bloom||Pears, Apples|
|Size||Characteristic of variety, most fruits|
|Shape (fullness)||Stone fruits|
|External Color||All fruits (e.g. ground color change in Golden Delicious, over color changes in red or purple fruit)|
|Seeds (darkening)||Pome fruits|
|Firmness (pressure tests)||Pome and Stone fruits|
|Soluble Solids||Pome, stone, kiwi|
Postharvest Handling and Storage
[PDF] Safe Handling of Fruits and Vegetables, Christine Bruhn, Amy Li-Cohen, Linda Harris, Anne Spitler-Kashuba
[PDF] Key Points of Control and Management for Microbial Food Safety: Edible Landscape Plants and Home Garden Produce, Trevor V. Suslow, Linda Harris
[PDF] Producing Quality Almonds: Food Safety Starts on the Farm, Bruce Lampinen, Joe Connell, Almond Board of California
[PDF] Oranges: Safe Methods to Store, Preserve, and Enjoy, Jennifer Snart, Mary Lu Arpaia, Linda Harris
[PDF] Apples: Safe Methods to Store, Preserve, and Enjoy, Linda Harris, Sylvia Yada, Elizabeth Mitcham
Fruit remains alive and respires after it is harvested. Lowering storage temperatures will slow the respiration rate and enzymatic activity of the fruit and prolong storage life. Freezing damages fruit.
Objectives in good harvesting and handling practices are:
- Harvest when fruit is mature
- Place fruit in optimum conditions for maximum storage life
- Be able to ripen fruit to full quality
The publication [PDF] Storing Fresh Fruits and Vegetables for Better Taste from the Postharvest Technology Center provides excellent guidelines.
Optimum temperatures to ensure longer storage life vary among commodities. Important storage principles are:
- Fruit stored at higher temperatures respire more than at lower temperatures. Heat/respiration generated at 32°F may be 1/10 of that generated at 60°F.
- Time-temperature effects are dramatic: apples ripen in 3 days at 70°F and 30 days at 30°F.
- High relative humidity usually promotes storage life and fruit quality.
There are many methods for providing fruit storage. The goal is to do whatever is possible and practical to meet optimum storage requirements and ensure high fruit quality. Methods include:
- Refrigeration (large or small)
- Cellars, basements
- Store outside (protect from sun, rain, rodents, etc.)
- Air conditioners, swamp coolers, under tarps
- Process, freeze, can, and/or dehydrate for home use
- Controlled atmosphere (commercial)