As pineaple has a CAM (crassulacean acid) metabolism, the carbon 12/13 ratios for pineaple lie between those for C3 and C4 plants making the use of carbon isotope ratio detection of exogenous sugars very challenging. The detection of beet (C3) and (C4) cane and maize based sugar adulteration of pineapple juice has not even been possible using site specific deuterium/hydrogen ratios (2H/1H) by quantitative deuterium nuclear magnetic resonance (SNIF-NMR) of the ethanol fermented from the pineapple juice sugars because of changes during the fermentation. IAEA scientists have developed a new GC-IRMS-based stable hydrogen isotope method, which utilises the trifluoroacetate derivative of sucrose to allow direct measurement of the carbon-bound non-exchangeable hydrogen. This provides advantages over alternative isotopic methods in terms of analysis time and sensitivity. This feasibility study has demonstrated the potential to reliably differentiate between authentic pineapple juices and those adulterated with commercial beet and cane sucrose.
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