This project examined the cooling rates of chestnuts after harvest, the effect of storage temperature on quality and the freezing point of chestnuts.
Why study this?
A 2013 project AHR conducted for the chestnut industry identified some inefficiencies in the way chestnuts were handled and stored. It seemed possible that growers could reduce their costs without affecting quality.
What was done
Temperature data loggers with probes were used to monitor the internal temperature of chestnuts cooled in bins in a room, in sacks, using a hydrocooling system or by forced air.
A separate experiment cooled chestnuts to between 0 and minus 7° C. These were stored for a week then examined for signs of freezing injury. Several varieties of chestnuts were stored for up to eight weeks at 0 or 3° C to compare quality at these storage temperatures.
What we found
Chestnuts cooled fastest and without significant weight loss in the forced air system. Bin cooling was relatively slow, and if a liner was added then cooling times increased to several days. This resulted in clear loss of quality.
Freezing damage was highly variable and was related to time as well as temperature. More than two hours exposure to minus 3° C often caused injury, while all fruit were damaged by even a brief exposure to minus 4° C.
There was little obvious damage of chestnuts stored at different low temperatures, suggesting that storage temperatures could be increased to 2–3° C without substantially affecting quality.
Where to next?
There are plans to include more information on storage, handling, preparation and cooking on packaging, both for retailers and for consumers. Pre-packs with information for consumers unfamiliar with chestnuts appear to have great potential to increase consumption. As varieties vary widely on ease of peeling and flavour, this information could be pivotal in increasing consumer satisfaction.
Growers can use forced air cooling to more efficiently cool their fruit without significantly increasing costs, while maximising use of existing resources. Increasing temperatures from the minus 3° C commonly used by many growers avoids potential development of rancidity and will reduce costs without impacting quality.
For more information contact
Dr Jenny Ekman, Applied Horticultural Research Pty Ltd