This paper (open access) recommends the use of sorbitol as an endogenous isotopic reference marker compound for the detection of C4-type sugar adulteration in apple juice.
Apple juice is traded mostly as concentrate because it is more efficient to transport and store than single-strength juice. It is valued according to its Brix measurement. There is therefore a motivation to add sugars (increasing the Brix) in order to – in turn – mask dilution. . Most cheap commercial sugars originate from C-4 plants, and chemical components may therefore have a different carbon isotopic ratio to equivalent chemical components originating from the unadulterated apple juice
The authors present an improved analytical method which utilizes the naturally occurring sorbitol in apple juice as an isotopic reference marker. The method uses liquid chromatography coupled to isotope ratio mass spectrometry (LC-IRMS) to determine the δ13C values of the major endogenous sugars in apple juice.
They report that the δ13C value of sorbitol can be measured in the same analytical run as the other major sugar components and remains unaffected by the addition of exogenous C4-type sugars to the apple juice. A difference between the sorbitol's isotope ratio and that of other components is therefore an indicator of adulteration.
They conclude that this method offers significant advantages over existing approaches, notably by eliminating the need for extensive sample preparation and multiple analytical methods thereby improving both analytical throughput and ease of use.
The authors of this paper include scientists from two of the laboratories in FAN’s Centre of Expertise network; GfL and Fera Science.
Photo by Katrin Hauf on Unsplash
