Survey of South African fruit juices using a fast screening HILIC-MS method

Abstract

Adulteration of fruit juices – by the addition of sugar or other less expensive fruit juices as well as preservatives, artificial sweeteners and colours – was tested for by using a developed screening method. The method employs hydrophilic interaction liquid chromatography-mass spectrometry (HILIC-MS) using electrospray ionisation in the negative mode and ultraviolet light detection. Different fruit juices can be differentiated by the content of marker compounds like sorbitol, certain phenolic molecules and their saccharide profile. This method was used to test 46 fruit juice samples from the retail market as well as 12 control samples. The study focused on the main types of fruit juices consumed on the South African market including apple, orange, grape and blends of these juices with other fruits like mango, pear and guava. Overall, the 46 samples tested mostly agreed with label claims. One grape juice sample was adulterated, probably with apple juice. Natamycin above the legal limits was found in two samples. In addition, two samples contained natamycin and one sample benzoate without it being indicated on the label. The method is well suited as a quick screening method for fruit juice adulteration and if used routinely would reduce fruit juice adulteration without the cost of the current array of tests needed for authenticity testing.

Keywords:

• fruit juice
• quality control
• adulteration
• LC-MS
• HILIC

Acknowledgements

The National Research Foundation (NRF) and the University of Stellenbosch are acknowledged for financial support (7441). The South African Fruit Juice Association is thanked for support with advice, as well as Luritha Moore from Appletiser and Heleen Pistorius from the Associated Fruit Processors for the supply of authentic control samples and fruitful discussions.