Oxygen isotope ratios of juice water in Australian oranges and concentrates

Abstract

Australian orange juices from major growing regions have been surveyed over a 5 year period with a view to establishing a database of 18O/16O isotope ratios against which retail samples can be tested for authenticity. The 18O/16O ratios were found to follow a consistent pattern that had both a cyclic seasonal and a regional influence. Oxygen delta values ranged from a summer maximum of >+15‰ for oranges from inland regions to a winter minimum of ~+1‰ for oranges grown in coastal areas. However, over a shorter time period, the range of values was markedly less than this. Concentrated orange juices, pulpwashes, and peel extracts, as well as other citrus types, were also tested. The effect of some industry practices that have an effect on 18O/16O ratios was also investigated.