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 minimal ly processed (removal of roots and compressed stem) green onions (Allium ce pa 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 v isual 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 ext ension, growth or 'telescoping' of the inner white leaf bases of the minima lly 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-tr eated cut onions. Heat treatment did not affect thiosulfinate concentration s during 14 days at 5 degrees C, except for treated cut onions not stored u nder CA. (C) 2000 Elsevier Science B.V. All rights reserved.