Chestnuts can be preserved using different techniques, whether they are freshly harvested or processed. This article explores traditional methods suitable for small quantities and modern approaches for large harvests.
Learn how to preserve chestnuts stay fresh and delicious throughout the winter months.
Preservation Techniques for Chestnuts
The most commonly used method for preserving chestnuts is curing. This method allows you to keep the fruit fresh so you can enjoy it leisurely during the winter months. There are also other preservation and transformation methods, some simple and suitable for home use, and others more elaborate, requiring specific structures. Let’s explore them all.
Curing, or the chestnut novena, is the simplest preservation technique for the iconic autumn fruit. It is easy to do even for occasional gatherers or those with only a few trees. It doesn’t require prohibitive spaces. The system is simple and allows you to preserve freshly harvested chestnuts for many months. Essentially, you immerse the chestnuts in water for nine days (novena), changing the water at established intervals. The tools needed for this process are essentially containers (large pots, hard plastic tubs, aluminum drums, etc.) spacious enough to hold the fruits and cover them with water. Of course, the more chestnuts, the more containers you’ll need. You’ll also need adequate space for drying, but let’s go through the chestnut novena step by step.
Before immersing the chestnuts in water, it’s a good idea to sort them, removing any that are rotten or show obvious signs on the outside. Then, immerse the remaining chestnuts in clean, room-temperature water. By the end of the first day, you might notice some chestnuts floating; these should be removed as they are damaged inside. Here are the steps for changing the curing water:
- From the 1st to the 4th day, change 50% of the curing water;
- On the 5th day, completely change the water;
- On the 6th and 7th days, change 50% of the water;
- On the 8th day, completely change the water;
- On the 9th day, remove the chestnuts from the water.
Why Does Curing Preserve Chestnuts?
Let’s understand why chestnuts are preserved through curing.
The immersion in water kills aerobes, the microorganisms responsible for the development of molds and fruit rot due to the absence of oxygen. After the initial days of immersion, anaerobic microorganisms develop, stimulating a mild fermentation, which produces a small amount of lactic acid inside the fruit. This allows the chestnuts to be preserved for a long time.
After the novena, the chestnuts taken out of the water need to be dried. Spread them evenly and without excessive heaps (no more than 5/10 cm) on a surface. This surface can be a wooden board, although a steel surface would be better. During the drying process, which should occur in a cool, ventilated room, move the fruits frequently. The drying time is 7 days.
Final Storage of Chestnuts
At this point, you need to store the chestnuts. It’s ideal to put them in jute bags that allow air circulation and prevent moisture (you can find bags here).
They can be kept in a fairly cool storage area, similar to what we discussed for potato storage. If the conditions are right, they can be preserved for up to 6 months. Small quantities of chestnuts can be stored in the fruit compartment of a refrigerator. Chestnut farms that preserve fresh fruit use refrigerated cells after curing.
The simplest home method for preserving chestnuts is freezing. Of course, this preservation method suffers from limited space unless you have access to chest freezers like these. Chestnuts in the freezer are preserved fresh, meaning raw, but they are destined for further processing. An example is oven-roasted chestnuts or boiled chestnuts. If you want to roast them before putting them in the freezer, you’ll need to score them so they’re ready for the oven or the perforated pan on the fire. If your intention is to boil them in water, you can freeze them as they are. They can be stored in the freezer for 12 months.
The Root Cellar Method
An ancient method for preserving chestnuts is the root cellar method. Essentially, a large pit is dug in the ground, where sand is placed at the bottom. Then, chestnuts are placed there, still in their husks, and covered with dry leaves, dry husks, and sand. This method allows chestnuts to be preserved for many months. However, it’s a method no longer widely used due to fruit losses caused by underground pests and the development of molds.
A more complex method for preserving chestnuts, which requires adequate space, is drying. In the past, it was done in specific structures called grà or metato. Fresh fruits are placed on a reed, which is a net-like scaffold built inside the building. These buildings are very simple, made of masonry with a roof of stone slabs. Chestnuts are laid out in a uniform layer of about 70 cm on the scaffold. Then, a fire is lit in the center of the building’s floor and under the scaffold. This fire must remain lit for a long time, even up to 40 days, until the fruit is completely dried, thanks to the smoke.
Beating and Roasting
Once dried, chestnuts are beaten to separate the fruit inside from the shell. They can be preserved as they are, to be consumed as snacks or rehydrated later. Alternatively, they can be taken to mills for the production of chestnut flour.
The described process is now obsolete and is practiced only by a few chestnut growers for niche productions. Today, chestnuts are dried in modern dryers that quickly process large quantities. These are then destined for transformation, thanks to specific peeling machines.
Other Industrial Methods for Preserving Chestnuts
Naturally, the industry preserves chestnuts in many other ways. One of these methods is thermization, which involves immersing the fruit in hot water at a temperature of about 50 °C for 45 minutes. The fruits are then immediately transferred to cold water tanks to stop the heating process and left immersed for 8-12 hours. Afterwards, they undergo a short curing process (about 5 days). Many industries freeze large quantities after peeling. Freezing occurs with rapid freezing in special tunnels operating at -40 °C. Chestnut preservation then takes place at -20 °C. Once thawed, they are sold as fresh products, mainly for confectionery transformation.
Further Reading on to Preserve Chestnuts
Harvest, Treatment, and Preservation of Chestnuts – Mauro Jermini, Thomas Sieber, Alberto Sassella.