- Malheur Experiment Station
Proper holding and storage of onions requires special care and attention. Storage life is highly dependent on the type of onion and how well they were dried. Holding temperature should be no higher than 33° F with a relative humidity range from 65 to 70 percent for dry onions. Proper storage specifications for bunched green onions differ in holding temperature, duration, and relative humidity (Matson, 1985; Opara, 2003). Higher temperatures within the holding facility (typically above 35°F), promote sprout growth, while high relative humidity can encourage the growth of roots and rot-causing fungi and bacteria (Adamicki, n.d.; Matson, 1985). Low relative humidity (less than 60%) can cause dehydration and even splitting of the onion bulbs (Opara, 2003). Temperatures below freezing, -1°C to -2°C (30°F to 28°F) will require that onions be thawed near 5°C (41°F) at least 1-2 weeks before being removed from storage (Adamicki, n.d.).