Use of controlled atmospheres and heat treatment to maintain quality of intact and minimally processed green onions

To maintain high quality and to extend the shelf life of intact and minimally processed (removal of roots and compressed stem) green onions (Allium cepa x A. fistulosum), the potential benefits of controlled atmospheres (CA) and heat treatment were evaluated. Atmospheres of 0.1-0.2% O-2 or 0.1-0.2% O-2 containing 7.5-9% CO2 were the CA conditions that best maintained the visual appearance and prolonged shelf life to more than 2 weeks at 5 degrees C in both intact and cut onions. No CA treatment completely controlled extension, growth or 'telescoping' of the inner white leaf bases of the minimally processed onions at 5 degrees C. Heat treatment (55 degrees C water for 2 min) of the white leaf bases effectively controlled 'telescoping' of cut onions stored at 5 degrees C. Total soluble sugars generally decreased in intact and minimally processed green onions, but were maintained in heat-treated cut onions. Heat treatment did not affect thiosulfinate concentrations during 14 days at 5 degrees C, except for treated cut onions not stored under CA. (C) 2000 Elsevier Science B.V. All rights reserved.