Oxygen isotope ratios of juice water in Australian oranges and concentrates

Australian orange juices from major growing regions have been surveyed over a 5 year period with a view to establishing a database of O-18/O-16 isotop e ratios against which retail samples can be tested for authenticity. The O -18/O-16 ratios were found to follow a consistent pattern that had both a c yclic seasonal and a regional influence. Oxygen delta values ranged from a summer maximum of >+15 parts per thousand for oranges from inland regions t o a winter minimum of similar to+1 parts per thousand 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 so me industry practices that have an effect on O-18/O-16 ratios was also inve stigated.