Stefanie Hellbach (1), Paul Rösch (1,2), Stephan Schwarzinger (1,2)
ALNuMed GmbH, Bayreuth (1)
Research Center for Biomacromolecules, University of Bayreuth, Bayreuth (2)
Consumers complaining about the quality of a brand product or, even worse, a critical media report by a consumer organization always cause significant costs in trade. In recent years, falsely labelled products pretending superior quality, premium provenance or premium variety caused dramatic losses in consumer confidence, resulting in a loss of faith in product declarations of a large number of consumers. To guarantee the value of store products it is therefore of utmost importance to ensure their quality and authenticity. For both, raw materials and end products, magnetic resonance (MR) based ingredient profiling offers a quick and versatile way to simultaneously screen quality and authenticity, in particular when applied to fruit juice, wine, honey, edible oils and related foods.
Food fraud is the modern spectre producers, retailers and entire branches of the food industry are afraid of. Scandals such as the horse-meat issue weaken consumer confidence – not only in products of single “black sheep“, but rather in much of the food industry. Thus, products with fraudulent declaration, if or when discovered, damage all participants of the value chain.
Fraud identification is a very difficult task, as adulterations are in many cases performed with great care and expertise. Rare are those cases in which a single parameter identifies an adulteration. Often, an adulteration is cleverly masked by addition of a blend of ingredients. Particularly difficult to uncover is food-origin laundry, that is the fraudulent labelling of food with a wrong geographic location. Although numerous expensive and time-consuming analyses are often being conducted to reveal food-origin laundry, it is difficult to obtain even close to 100 % confidence.
SGF (Sure-Global-Fair) Juice-Profiling (1), originally developed and now continuously maintained with support of SGF International (www.sgf.org), and BatchCheck are cost and time efficient alternatives that are based on the magnetic resonance spectra of the foodstuff to be tested. SGF Juice-Profiling relies on a single quick measurement that allows it to quantitatively assess numerous ingredients. Magnetic resonance spectroscopy has a unique dynamic range and high resolution, rendering simultaneous quantification of dozens of substances possible at very high and very low concentrations within a short measurement.
Very simple sample preparation adds to robustness and reproducibility of the method. For instance, this juice profiling method allows a quick estimate of the concentrations of sugars, organic acids and amino acids, replacing costly and time-consuming traditional analyses and allowing the comparison of the spectral fingerprint with a database of thousands of authentic samples. Thus, fruit type, geographic origin, fruit content and even unexpected and yet unknown adulterations can be quickly screened. Even if the results from the juice profiling were not perfectly conclusive, usually based on the composition an efficient and inexpensive route for additional analysis – if needed at all – can be delineated of the basis of the profiling results. At present, SGF Juice-Profiling is available for more than 30 fruit types and delivers up to 37 quantitative results in addition to authenticity testing (fruit dependent).
Adulteration frequently occurs along the trade-chain. Consequently, merchandise samples and delivered batch are not always identical. BatchCheck takes advantage of the high resolution and the unmatched reproducibility of magnetic resonance spectroscopy regarding quantitative information. The procedure relies on the comparison of the quantitative spectral fingerprints of the merchandise sample and a sample drawn from the delivered batch. By contrast to, e.g., stable isotope methods, where typically a handful of parameters are used for such comparisons, BatchCheck utilizes several hundreds of signals available from the magnetic resonance spectrum (Figure 1). Using statistical methods fingerprints of the merchandise sample and the batch that was finally sold are compared in back-to-back measurements with highest sensitivity in the shortest possible time. In the case of deviations of the two samples that are being compared, combined with the quantitative evaluation available from SGF Juice-Profiling can aid identification of deliberate adulteration, dilution or quality defects resulting from inappropriate storage before, during or after transportation.
Today, magnetic resonance based profiling tests are routinely applied for quality and authenticity screening of fruit juices, wines and honey. Applications include testing of raw materials as well as finalized and packaged products. The method is applied by the private sector as well as governmental agencies. Utilization of a centralized ISO 17025 accredited evaluation method in combination with the outstanding reproducibility of the magnetic resonance technology, maximum comparability and reproducibility of results is ensured. SGF Juice-Profiling has been applied for over 10 years in the market. The Honey-Profiling (2,3) module that was added recently expands the capabilities of the profiling method. With this newly available module it is possible to quickly screen for adulteration of honey, an important ingredient for many fruit juices. Hence, magnetic resonance based profiling offers significant advantages for time and cost savings in production, and can make an important contribution to regain lost consumer confidence.
Figure 1: ALNuMed’s BatchCheck relies on the quantitative information of hundreds of signals available from a magnetic resonance ingredient fingerprint. In the above, two expansions of such ingredient fingerprints are shown (10 % of total fingerprint; magnetic resonance scale in ppm [parts per million], intensity scale in arbitrary units). The right panel shows fingerprint traces from two different batches of a fruit puree, while the left panel depicts ingredient fingerprints of two samples of the same batch. It can clearly be seen that the fingerprints of samples from different production batches differ significantly – despite resembling the same fruit type. By contrast, the fingerprints of the same sample depicted in the right panel are essentially identical. The region selected typically shows signals of phenolic substances, which are present at comparatively low concentrations. Of note, from the same measurement magnetic resonance allows quantification of ingredients present at much higher concentrations, including sugars and organic acids. The resulting quantitative fingerprint differs in quality and reproducibility form other available technologies and even allows testing for fruit variety, dilution, and geographic origin of the fruit with SGF Juice-Profiling.
(1) Spraul M et al.: NMR-Based Multi Parametric Quality Control of Fruit Juices: SGF Profiling. Nutrients 1(2), 148-155 (2009). doi: 10.3390/nu1020148
(2) Schwarzinger S et al.: More than honey? Rapid authenticity testing of honey with NMR spectroscopy and consequences for sample preparation. Q&More 2, 36-43 (2014). http://rs1.chemie.de/images/23940.pdf
(3) Schwarzinger S et al.: Authentic food: Why a single analysis parameter is not enough. Q&More 1, 37-43 (2016). http://rs1.chemie.de/images/30172.pdf