Storing, Handling, Preparing, and Consuming Chestnuts

There are three not widely known pieces of information in the chestnut industry associated with getting fresh chestnuts to the consumer and the consumer preparing and eating chestnuts. These are:

1. Not all chestnuts taste the same
2. Fresh chestnuts can be sweetened up
3. Poor handling of chestnuts affects nut quality

Not all chestnuts taste the same
There are many factors associated with the taste of chestnuts. The two most important are the chestnut cultivar and the growing conditions. In the commercial fresh chestnut industry worldwide, there are three types of chestnuts: Chinese, European, and Japanese. Most of the chestnut production is based on hybrid combinations of these three. One of the most popular commercially grown chestnut trees in the United States is the Colossal chestnut. Growers like this tree because it produces large chestnuts (nuts up to 2 inches across). The Colossal is a hybrid of European and Japanese type chestnut trees. Taste tests done in small groups using chestnuts from several different hybrid chestnut trees shows that the best tasting type of chestnut is very dependent on who is doing the tasting. So, yes, there is a taste difference between chestnut cultivars and the entire profile of taste parameters contribute to the taste impression.

Fresh chestnuts can be sweetened up
This has got to be the best kept secret about chestnuts. When chestnuts fall from the tree, the nuts are high in complex carbohydrates. Chestnuts can convert some of these carbohydrates into sugars if the conditions for this process are met. Like many of the best things in life, this conversion process or sweetening of chestnuts requires time, the right temperature, and some special handling. The process also requires oxygen (sealed plastic bags will not allow the chestnuts to undergo the sweetening process).

Time - the easy part. This is partially dependent on temperature and humidity. Generally, the sweetening process takes between 1 and 4 days. Care must be taken not to dry out the chestnuts because they will get hard as concrete. In a recent study the sweetness of the chestnuts reached a peak on the 3rd day. This study held the chestnuts at 70 degrees F with the humidity at 60-70%. The study demonstrated that it is best to only allow the chestnuts to sweeten at room temperature for at least 2 days but not more than 4 days. Longer curing times results in the loss of flavor and sweetness.

Temperature - Room temperature of between 65 and 75 degrees F

Special handling - The chestnuts must be placed on a flat surface in a single layer with good air circulation. If mold starts to develop (white or black spots appearing on the outside of the chestnut shells), wash the chestnuts right away, dip them in a mild bleach solution, and then place them back on the flat surface with more spacing between the chestnuts to increase air circulation.

The best way to tell if the chestnuts have sweetened up is to cook one and eat it. When the chestnut is peeled, observe the color of the nut kernel. You are looking for a nice yellow color (depending on the type/cultivar of the chestnut) throughout the kernel.

Poor handling of chestnuts affects nut quality
Chestnuts are consumed in a high moisture and low oil state. In this state chestnuts are susceptible to going bad. Freshly fallen chestnuts are about 50% water (we can call this their wet state). When fully dried they contain about 7 - 8 % water (this will be called their dried state). When dried, chestnuts are stable and can be stored for months in sealed containers (keeping the bugs out of the chestnuts). Between the wet state and the dried state, chestnuts are susceptible to rotting. Rotting comes in the form of spoilage from molds, yeasts, and fungus as well as freezing and thawing. Instead of going through all the food science talk of keeping food from going bad, lets just make a list of good handling practices for chestnuts.

1. Do not let fresch chestnuts freeze and thaw (except if you are freezing for a purpose)
2. Never store chestnuts in a sealed plastic bag (except dried or frozen)
3. Keep chestnuts refrigerated unless drying or sweetening the chestnuts
4. If black molds have entered into the chestnut kernel, do not eat the chestnut
5. Chestnuts can be stored in the refrigerator for 2 to 3 weeks
6. Cooked chestnuts must also be refrigerated if not consumed right away
7. Never bathe the chestnuts in plain water - this causes mold spores to be transferred to all the chestnuts passing though the bath water - instead, wash in clean running tap water
8. Try to purchase fresh chestnuts close to the time you want to eat them