This study (open access) used the fingerprint of trace elements (measured by inductively-coupled plasma – mass spectrometry, ICP-MS) as a marker for the use of mineral vs organic fertilisers, and hence as a marker for the mislabelling of Organic apple juice. The concept was proven on juices made from apples grown in two regions of Northern Germany.
Reference data sets were generated from juices made by the researchers from apples of known provenance. 59 apple juice samples (31 organic and 28 conventional) from four crop years (2020–2023) were analyzed regarding their element profiles and used for model creation. All samples were from Schleswig-Holstein, Germany. Afterwards, the model was expanded using 24 apple juice samples (11 organic and 13 conventional) from Hamburg, Germany (crop year 2020–2023). Prior to analysis, the whole apple samples were washed with deionized water and then dried. Afterwards, the samples were processed to apple juice using a commercial juice extractor.
The authors report that, using an environment-friendly sample preparation strategy and a ratio-based evaluation approach in combination with a random forest classification model, it was possible to distinguish between the cultivation methods of processed apples. The results were verified by analyzing samples from local supermarkets. Furthermore, the detection of adulterated mixtures of conventional juice to organic juice was studied using a regression analysis (5–50 % adulteration). Adulteration could reliably be detected from a proportion of 20 % Thus, falsification of the cultivation method can be detected even in mixtures.
The authors conclude that the study shows great potential towards sustainability, reducing sample preparation time, hazardous chemicals and energy consumption. The identified molybdenum as a potential routine marker for organic apple juice.
