Ascorbic acid, aroma compounds and browning of orange juices related to PET packaging materials and pH

The ascorbic acid content of orange juice made from concentrate was measured after 9 months of storage at 20 °C in glass, standard monolayer polyethylene terephthalate (PET 1 ), multilayer PET (PET 2 ) and plasma‐treated PET (PET 3 ) containers. Glass enabled the best preservation of ascorbic acid and, in plastic packaging materials, ascorbic acid losses were correlated with their oxygen permeability. PET 2 and PET 3 , which exhibit oxygen permeability 10 times less than that of PET 1 , enabled a gain of 100 mg L −1 after 9 months of storage. Freshly hand‐squeezed orange juice samples were adjusted to various pH values using sodium hydroxide; a rise in the pH from 3.2 to 4.0 significantly reduced the amounts of off‐flavours (i.e., furfural and α‐terpineol) appearing during storage, by 79% and 65%, respectively. Moreover, an increase in the pH from 3.2 to 4.0 enabled the protection of ascorbic acid levels without detrimentally increasing non‐enzymatic browning. Copyright © 2006 Society of Chemical Industry