Detection of Origin of Vitamin C in Fruit-Containing Products and Supplements
by Lars Reimann

Issue Date: April / May 2009

Ascorbic acid is the main component of Vitamin C.  It is one of the key nutrients emphasized in nutrition claims promoting health benefits of fruit containing products including juices and supplements.  Such claims often refer to the natural source of this component: “Naturally rich in vitamin C” or “Contains natural Vitamin C” and have ingredient labels that do not list added vitamin C.  However, ascorbic acid is also available as an additive manufactured through a fermentation process involving various sugar sources.  There is therefore a need for an analytical tool capable of differentiating ascorbic acid from fruits from ascorbic acid from other sources. 

Since the range of ascorbic acid concentrations in fruits can vary widely, fairly large additions of extraneous ascorbic acid can go undetected by conventional methods. This means that stable isotope methods are the best and often only technologies for differentiating between endogenous and exogenous sources.  Recently it was shown that a comparison of the global 13C/12C ratio with the 13C/12C ratio of the carboxyl carbon of ascorbic acid enables the detection of industrially manufactured ascorbic acid regardless of the origin of the starting material used. 

The new method is based on the chemical cleavage of the ascorbyl carboxylic acid group, followed by direct injection of the CO2 formed into an isotope ratio mass spectrometer.  This method was developed and validated as part of an EU-funded project (1).  It is applicable to all fruits containing a high concentration of vitamin C (>200mg/liter for juices; >200mg/100g for supplements) such as citrus, blackcurrant and acerola products.  The sensitivity of this approach depends on the sample type and the source of extraneous Vitamin C but is around 15% for most juice products.

Eurofins offers a package that includes the determination of both the global and positional 13C/12C for the ascorbic acid, the global 13C/12C for the sugars present (used as internal reference value)  as well as the determination of the ascorbic acid content.  It is one of the many batteries of tests Eurofins has established as part of its investment in R & D to improve the analytical tools for adulteration detection and confirm its reputation as one of the leading labs for authenticity testing.

For further information please contact Lars Reimann at LarsReimann@EurofinsUS.com.

 (1) PURE JUICE, a shared project funded under the Fifth Framework Programme of the European Community, Contract No. G6RD-CT-2002-00760