Chestnut Storage Limit Study

Goal: To establish storage limits of fresh chestnuts when post harvest handling is performed to food industry safety standards with a target of 12 weeks post harvest consumer stable fresh chestnuts

Background: Fresh chestnuts have a limited storage life before they start to rot. This study tested the storage life of fresh chestnuts from harvest until the chestnuts started to germinate. During the study several chestnuts were removed and periodically examined for rot and taste panel tested to check if the taste was impacted by the length of storage.

Methods: The chestnut cultivar used in this study was Bisalta #3, harvested in mid October of 2010. The Bisalta #3 is a European (C. sativa) – Japanese (C. crenata) hybrid cultivar originating from Italy. This cultivar was chosen only because of its abundance at harvest time. The chestnuts were allowed to fall to the ground and were hand harvested daily. No nuts were allowed to stay on the ground overnight.

The chestnuts were then washed with a continuous stream of domestic water supply and then placed in a sanitizing solution for about 2 minutes. The nuts were allowed to air dry before being placed in a 1 gallon plastic bag with a seal strip. The sealed bag was then placed in a refrigerator for the entire study period. The sealed bag was opened each time chestnuts were removed for examination for signs of rot and taste panel testing.

The taste panel was asked to evaluate several chestnuts removed from storage at random intervals. The chestnuts to be tested were cooked in a microwave oven to provide the most consistent cooking conditions. The taste panel evaluated flavor, texture, and sweetness. The chestnuts were allowed to cure or sweeten at room temperature for between 1 and 5 days to also evaluate when chestnuts reached their optimum sweetness to taste.

Terms:

• Fresh Chestnut: Fall harvested chestnuts that are collected from the orchard daily
• Rot: Yeasts, molds, and fungus present and observable on the chestnuts
• Refrigeration: Storage temperature of 38 degrees F (3 degrees C)
• Safe food handling standards: Government of Australia - Food Safety Standard 3.2.2 - Food Safety Practices and General Requirements
• Curing or sweetening chestnuts: Allowing the chestnuts to convert store carbohydrates to sugars usually at room temperature (65 – 75 F)

Storage Log:

10/21/2010 – Harvested and processed 2 pounds of fresh Bisalta #3 chestnuts through a rinse and a sanitation bath then air dried the chestnuts. After air drying for 1 hour the chestnuts were placed in a sealed plastic bag and moved to refrigerated storage at a temperature of 38 degrees F.

12/24/2010 – Examined the chestnuts in storage for signs of rot. No signs were present of molds, yeasts, or fungus. About 10 chestnuts removed for taste panel. The plastic bag resealed and placed back into refrigerated storage. Taste panel reports the chestnuts remain flavorful and the texture has not degraded for the texture at harvest time.

1/17/2011 – Examined the chestnuts in the storage trial. Of the remaining chestnuts in this trial only 2 nuts had tiny spots of mold. No signs of fungus or yeasts. The 2 chestnuts showing signs of rot were removed from the trial batch. Also removed 10 chestnuts for evaluation by the taste panel and placed remaining chestnuts back into refrigerated storage. The taste panel reports the chestnuts remain sweet with only a slight degrading of texture as compared to harvest time.

2/11/2011 – The last of the chestnuts in the storage trial were removed and the study was terminated. About 10% of the chestnuts were showing signs of germinating. There were no additional signs of rot on any of the nuts. The taste panel reports the chestnuts remain sweet and flavorful but the texture has changed enough to rate the chestnuts as consumer stable but lacking the fresh tasting. Only a very discerning pallet would be able to detect the minor quality change.

Conclusion:

If all fresh chestnut cultivars responded the same during storage, fresh chestnuts can be stored for about 100 days post harvest without significant losses to rot or reductions in quality and taste. This can only be accomplished by following food industry safe food handling standards with the post harvest handling of the chestnuts.

The taste panel’s evaluation of the curing and sweetening of chestnuts reaches the peak sweetness after about 3 days of curing. The curing in this trial was at normal room temperatures (68 – 70 degrees F) and the humidity was about 30%. Curing for longer than 3 days resulted in a reduction in the quality of the chestnuts. The reduction in quality can be attributed to the loss of moisture in the chestnut kernel. Curing for shorter than 3 days did not allow for the full sweetness of the chestnut to develop.