Charles Forney from the Atlantic Food and Horticulture Research Centre in Nova Scotia, Canada reports in HortScience that relative humidity, rather than temperature, was the key to extending the shelf-life of the berries.
The results appear to provide cranberry processors important information about methods for prolonging freshness and marketability of fresh cranberries, thereby ensuring fresher, wholesome, antioxidant-rich berries for further processing or for retail.
The study results appear as the 2008 cranberry crop is forecast to be the second largest on record, according to the USDA National Agricultural Statistics Service which anticipated 6.89m barrels this year, up five percent from 2007 and slightly below 2006.
Forney conducted his new study over three seasons to determine how the relative humidity and the temperature of the storage conditions would impact on the shelf-life on the cranberries.
Using fresh cranberries from four commercial bogs, Forney stored the berries at temperatures ranging from 0 to 10 degrees Celsius, in combination with different humidity levels, from 75 to 98 per cent.
"Fruit were stored under these conditions for up to six months and were evaluated monthly for marketability, decay, physiological breakdown, weight loss, and firmness immediately after removal and after an additional week at 20 degrees Celsius,” explained Forney.
“The percentage of marketable fruit declined substantially over time in all storage conditions, with 41 to 57 per cent becoming unmarketable after two months as a result of both decay and physiological breakdown."
The relative humidity had a greater effect on fruit storage life than temperature, concluded Forney. Specifically, after five months of storage, the amount of marketable fruit stored in high (98 per cent) and medium (88 per cent) relative humidity was 71 per cent and 31 per cent less than that stored in low (75 per cent to 82 per cent).
"Results suggest that cranberry fruit should be stored at 0 to 7 °C and 75% to 82% RH to retain marketable fruit," concluded Forney.
Cranberry benefits
The popularity of cranberries has been increasing in recent years as a combination of strong marketing campaigns and a body of scientific evidence revealing the fruit's health benefits has contributed to growing consumer awareness and interest in the product.
The fruit has long been considered an effective method of fighting urinary tract infections, something that has led to almost one third of parents in the US giving it to their children, according to a recent study.
In 2004 France became the first country to approve a health claim for the North American cranberry species Vaccinium macrocarpon, which states that it can 'help reduce the adhesion of certain E.coli bacteria to the urinary tract walls'.
Source: HortScience Volume 43, Pages 286-583 “Optimizing the Storage Temperature and Humidity for Fresh Cranberries: A Reassessment of Chilling Sensitivity”Author: C.F. Forney