|Infobox on Chestnuts|
|Example of Chestnuts|
|Stowage factor (in m3/t)||-|
|Humidity / moisture|
|Ventilation||10 - 20 a/c per hour|
|Risk factors||See text|
Castaneas are very large deciduous trees. They are monoecious, bearing both male and female flowers (“catkins”), in the same tree.
Chestnut (Castanea), some species called chinkapin or chinquapin, is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae, native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce.
Richly flavoured, starchy, chestnuts are popular cool season edible nuts of the northern hemisphere. The nuts are native to hilly forest of China, Japan, Europe, and North America. Botanically they belong to the beech or Fagaceae family of the genus: Castenea. Scientific name: Castanea sativa.
The fruit can be peeled and eaten raw, but it can be somewhat astringent, especially if the pellicle is not removed.
Another method of eating the fruit involves roasting, which does not require peeling. Chestnuts can also be peeled and deep fried.
Chestnuts can be dried and milled into flour, which can then be used to prepare breads, cakes, pancakes, pastas or used as thickener for stews, soups, and sauces.
The nuts can also be eaten candied, boiled, steamed, grilled, or roasted in sweet or savoury recipes. They can be used to stuff vegetables, poultry, fowl and other edibles. They are available fresh, dried, ground or canned (whole or in puree).
A fine granular sugar can be obtained from the fermentation of the juice, as well as a beer; the roasted fruit provides a coffee substitute.
Sweet chestnuts are not easy to peel when cold.
Chestnuts are often added to animal fodder.
Shipment / Storage
Chestnuts are usually shipped in cartons or bags.
Chestnuts suffer from ‘stanca’ (tiredness), causing deterioration in the appearance of the nuts. Such nuts can be refreshed in a cold water bath. This condition should not affect the value of the goods, as after being refreshed, they should fully recover. Under this treatment defective nuts float to the surface. Chestnuts respire, and during the respiration process moisture and gases are given off which, if not controlled by circulation of air, will cause heat and mould to develop.
Chestnuts under refrigeration will, if properly stowed and dunnaged, and proper temperatures maintained, remain in sound condition for several months (see below). There is a risk of deterioration after discharge if unloaded from refrigerated spaces into the hot sun. Once the process of deterioration has begun, it is difficult, if not impossible, to arrest. Chestnuts are liable to infestation and should be fumigated before shipment.
Chestnuts can be stored for extended periods (up to a year) by drying them completely and storing in a sealed container. Storing fresh chestnuts can be challenging. Fresh chestnuts do not store well even in refrigeration. Fresh chestnuts can go bad just as many other fresh food items do with moulds, fungus, bacteria, and yeasts.
Maturity Indices of fresh Chestnuts
The burrs begin to dehisce between mid September and early October (depending on the cultivar and production area) shedding the nuts. Chestnuts should be picked up daily during the harvest season to minimize fungal infection and growth (if infection occurred while the nuts are still on the tree) and loss of quality due to excessive drying and/or sunburn. Use of a tarp below the tree can reduce contamination of the nuts due to direct contact with the soil. Alternatively, a mechanical shake-catch harvester can be used. Following harvest the remaining burrs should be removed. Fresh chestnuts contain 40 to 60% moisture and should be handled with care to avoid mechanical damage.
- Size (larger nuts are preferred for fresh consumption)
- Shell color uniformity (tan to light-brown or dark-brown, depending on cultivar) and gloss (bright and shiny)
- Lump and fresh kernels (optimum eating quality at 25-30% moisture after roasting)
- Freedom from defects, such as bruising, cracking, sprouting, and decay
- Ease of pellicle removal (peelability) from the kernel; sweetness is a very important taste factor
- Chestnuts contain 40 to 45% carbohydrates-mostly starch which is converted to sugars when the chestnuts are kept at 20-25°C (68-77°F) for 3-4 days just before sale to consumers
- Absence of off-flavors
Temperature & controlled atmosphere (CA)
-1 to 0°C (30 to 32°F); highest freezing point is -2°C (28°F) for European chestnut and –5°C (22°F) for Chinese chestnut; prompt cooling to 0°C (32°F) is strongly recommended to stop decay development and preserve quality.
Optimum Relative Humidity
90 – 95%; packaging in microperforated plastic film is highly recommended to minimize water loss from fresh chestnuts.
Rates of Respiration
2.5-3.5 ml CO2/kg•hr at 0°C (32°F) 7.5-10 ml CO2/kg•hr at 20°C (68°F) 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
<0.01 µl/kg•hr at 20°C (68°F)
Responses to Ethylene
Preharvest or postharvest exposure of burrs to 50-100 ppm ethylene gas or 500-1000 ppm ethephon (ethylene-releasing liquid) accelerates dehiscence. There are no reported effects of ethylene on the nuts.
Responses to Controlled Atmospheres (CA)
An initial exposure to 40-50% CO2 for 5-7 days at 0°C (32°F) followed by storage in a CA of 2-3% O2 + 15-20% CO2 is very effective in preventing mold growth, sprouting, and other quality deterioration factors. Exposure of fresh chestnuts to <1% O2 results in fermentative metabolism and off-flavor development. Under optimal temperature of –1 to 0°C (30 to 32°F), relative humidity (90-95%), and CA (2-3% O2 + 15-20% CO2), fresh chestnuts can be stored for up to 4 months.
Sprouting results from exposure to high temperature and humidity and can be avoided by using optimal storage conditions.
Several fungi (including Alternaria spp, Aspergillus niger, Botrytis cinerea, Fusarium spp, Penicillium spp, and Phomopsis castanea) can infect chestnuts and result in significant postharvest losses in quality and marketability.