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Australian orange juices from major growing regions have been surveyed over a 5 year period with a view to establishing a database of (18)O/(16)O isotope ratios against which retail samples can be tested for authenticity. The (18)O/(16)O 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 per thousand for oranges from inland regions to a winter minimum of approximately +1 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 some industry practices that have an effect on (18)O/(16)O ratios was also investigated.

The stable carbon isotope ratios of 122 samples of common liquors and nine fermentable substrates have been determined. The P C values of the liquors analysed reflected those in the plant from which the fermentable substrate was derived. These values ranged from -23.4 to -26.0%, relative to Pee Dee Belemnite (PDB) for substrates derived from C3 plants while those from CB plants ranged from -10.3 to -11.8%, PDB. The application of this technique to detect the illicit extension of whisky has been investigated. As little as 2.9 % grape spirit or 5.7 % molasses spirit can be detected in whisky although the lower limit is dependent on the 8l3C value of both the authentic whisky and the diluent. Measurement of 13C : 1% ratios could also be used to check that imported brandies conform with local requirements.

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