Mass spectral analysis shows 100%-pure pomegranate juice. Source: PE.

Mass spectral analysis shows 100%-pure grape juice. Source: PE.

Mass spectral analysis shows adulterated pomegranate juice with 1% grape juice. All tests were done on a PerkinElmer AxION DSA/TOF MS system. Source: PE.

Pomegranate juice is not likely to be consumed in a 100 percent pure state as most people would find its flavor much too sharp—let alone its cost. So it’s usually mixed with other juices—which sweetens the flavor and makes the juice more affordable. Today pomegranate concentrate sells for between $30 and $60 a gallon, whereas apple or grape concentrate goes for about $5-7 per gallon. The real issue for beverage processors is how to determine if a product is of the concentration the COA (certificate of authenticity) promises.

If the concentrate was not purchased from a California producer, then it probably originated from a Middle East country such as Iraq, Afghanistan, Syria, Georgia, etc. But more likely than not, it was imported from a distributor in India, China or Russia. By the time it arrives on US soil, its contents may be far from what they started out to be, having been manipulated by anyone along the circuitous supply chain. In other words, some final products may be adulterated without the final bottler’s knowledge.

According to a case study from PerkinElmer (PE), Pomegranate Juice Alteration, traceability may be one issue, but adulteration or thinning the pomegranate juice with another juice is more important from a cost standpoint. Traditionally, chromatography combined with mass spectrometry has been used to detect marker compounds for both pomegranate and adulterant juices, according to Robert Packer, PE solutions development leader and author of the case study. The main issues with this technique are time and know-how. This testing method takes sample prep time as well as about an hour to actually run the test. It also assumes the operator is skilled and knows how to do the sample prep, run the equipment and interpret the results.

According to Packer, using a time-of-flight mass spectrometer (TOF MS) with direct sample analysis (DSA) can speed the test to around 10 seconds, and the test for adulteration can be run and understood by non-scientists. Tests were conducted with PE’s AxION DSA/TOF MS of pure pomegranate juice (Fig. 1), pure grape juice (Fig. 2) and pomegranate juice adulterated with 1 percent grape juice (Fig. 3).

Figure 1 shows the mass spectral profile of pure pomegranate juice; Figure 2, pure grape juice; and Figure 3, pomegranate juice with 1 percent grape juice as carried out on a PE AxION DSA/TOF MS system with juice pipetted directly onto steel mesh for analysis, with a gas temperature of 25°C, flow rate of 3 liters/min. and capillary exit voltage (-100 V) previously adjusted to maximize signal, providing an average mass accuracy of 5 ppm.

Figure 1 shows significant contributions from citric and malic acid in pomegranate juice. Figure 2 shows that grape juice also has malic and citric acids, but also has a contribution from tartaric acid. As this isn’t present in pomegranate juice, it can be used as a marker for grape juice addition to pomegranate juice. This is supported by figure 3 where 1 percent grape juice has been added to pure pomegranate juice, and the tartaric is still clearly viable. Thus, the juice is shown to be adulterated with grape or another juice containing tartaric acid.

The case study also looks at the effectiveness of UV/Vis spectroscopy and found it to be a viable method of determining whether pomegranate juice has been adulterated. The point the case study makes is: While these detection methods can be put to work in determining whether pomegranate juice has been adulterated, the results of these analyses need to be teamed up with appropriate tracing methods to track down those who may be guilty of cheating processors with intentionally weakened product. Once suppliers and distributors know their products can be checked to validate COAs, processors can begin to expect that the product matches the COA.

For more information, contact Robert Packer, 203-402-1814, robert.packer@perkinelmer.com

Download Pomegranate Juice Adulteration here.

For more information on the AxION DSA/TOF MS, visit PE’s web site.