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United States Department of Agriculture

Agricultural Research Service

Title: High Temperature Continuous Flow Curing of Sweet Onions

Authors
item Maw, Bryan - UGA
item Butts, Christopher
item Purvis, Albert - UGA
item Seabold, Kenneth - UGA
item Mullinix, Benjamin - UGA

Submitted to: Extension Reports
Publication Type: Other
Publication Acceptance Date: November 1, 2002
Publication Date: N/A

Interpretive Summary: Botrytis Neck Rot is one of the most prevalent diseases in sweet onions causing significant losses during storage. The fungus invades the onion bulb through dead or dying leaves of the onion plant and grow downward through the neck into the bulb. Vidalia Onions were cured for up to 24 hours using air temperature between 110-115 degrees Fahrenheit. . These onions were compared to onions cured for 72 hours at 95 degrees Fahrenheit. The progression of Botrytis Neck Rot during storage in onions cured with the high heat was reduced when compared to Vidalia Onions cured conventionally. The disease progression in onions cured at 115 Fahrenheit tended to be slower than those cured at 110 Fahrenheit. It was also lower in onions cured for 24 hours compared to those cured for 17 hours at elevated temperatures. By heat treating sweet onions, the progression of Botrytis Neck Rot could be reduced and may reduce storage losses by up to $20 million annually in Georgia.

Technical Abstract: A study was undertaken to investigate the feasibility of heat treating sweet onions under controlled commercial conditions. Three batches, approximately 2.5 tons each, were passed through a single pass continuous flow drier. Air temperatures of 43 and 46 C were used to cure sweet onions for 17 and 24-h. Samples of cured onions taken from the dryer at regular intervals and after prescribed storage durations were inspected for the presence of Botrytis Allii with the aid of a dye. Onions receiving heat treatment had significantly less increase in the infection by Boytrytis Allii than onions cured conventionally. Disease progress tended to be lower in onions treated for 24 h than those treated for 17 h and for those treated at 46 C compared to those treated at 43 C. The heat treatment was not sufficient to completely cure the onions. Therefore, a combination of heat treatment and conventional curing is needed to reduce losses due to Boytrytis Allii during storage.

Last Modified: 11/26/2014
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