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Title: EFFECT OF SEQUENTIAL TREATMENT OF WARM WATER DIP AND LOW DOSE GAMMA IRRADIATION ON THE QUALITY OF FRESH-CUT GREEN ONIONS

Author
item KIM, HYUN JUNG - UNIVERSITY OF ILLINOIS
item FENG, HAO - UNIVERSITY OF ILLINOIS
item TOSHKOV, STOYAN - UNIVERSITY OF ILLINOIS
item Fan, Xuetong

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2004
Publication Date: 4/1/2005
Citation: Kim, H., Feng, H., Toshkov, S.A., Fan, X. 2005. Effect of sequential treatment of warm water dip and low dose gamma irradiation on the quality of fresh-cut green onions. Journal of Food Science. 70:m179-185.

Interpretive Summary: Consumption of cut green onions (a seasoning vegetable in oriental dishes and Mexican cuisines) has been implicated in several recalls and outbreaks of foodborne illness. A recent outbreak related to raw or undercooked green onions served in restaurants in Pennsylvania killed 3 people and sickened nearly 600 others. Surveys conducted by the Food and Drug Administration (FDA) also showed a high rate of human pathogens in domestic and imported green onions. An effective food safety intervention for fresh-cut green onions is indispensable. This study was conducted in collaboration with University of Illinois researchers to explore use of gamma radiation in combination with warm water treatment to improve microbial safety and maintain product quality of cut green onions. Although warm water initially reduced the population of bacteria by 80%, the beneficial effect disappeared during storage. Irradiation reduced the population of bacteria by 99.9% on green onions and improved sensory quality. The information about the beneficial effects of irradiation can be used by vegetable processors to secure safety and quality of green onions.

Technical Abstract: The effect of warm water dip in combination with irradiation on quality of fresh-cut green onions was studied. Fresh-cut green onions were treated with and without warm water (50°C, 20 seconds) and packaged prior to irradiation at 0, 0.5, 1.0 and 1.5 kGy, then stored at 4°C for 14 days. Color, texture, decay percentage, electrolyte leakage, sensory qualities and total aerobic count (TAC) were measured at 1, 4, 8, and 14 days of storage. Although the warm water treatment reduced the total aerobic count by 0.9 log initially, the beneficial effect disappeared during storage. With the test conditions used in this study, the warm water treatment did not provide any benefit in terms of quality improvements. Irradiation at all tested doses reduced TAC and the development of decay and off-odor, improved visual quality, and preserved green color. Our results suggest that irradiation at doses up to 1.5 kGy can be used to extend shelf life of fresh-cut onions, and the warm water treatment prior to irradiation did not provide significant additional benefits.