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In an industry where food fraud and adulteration can undermine both quality and consumer trust, nuclear magnetic resonance (NMR) spectroscopy is emerging as a game-changing solution for juice authentication. Offering rapid, accurate and cost-effective analysis, NMR is poised to become the go-to method for verifying composition, detecting adulterants and ensuring regulatory compliance. Lea Heintz from Bruker Applied NMR explores this tech.

Economically motivated adulteration (EMA), or food fraud, refers to the intentional omission or substitution of a valuable part of a food product, or the addition of a substance to make the product appear to be of higher quality. Estimates suggest that food fraud affects approximately one percent of the global food industry, costing between $10 billion and $15 billion annually.

Illegal practices, such as diluting with water, adding artificial sweeteners and mixing pure juice with cheaper alternatives, deceive consumers and threaten the safety, quality and premium pricing of the juices being sold – undermining the integrity of the whole industry.

Consumers also value country of origin when choosing their juice. Research has shown that the buying customer associates certain juices as being of high quality when marketed as originating from certain nations – particularly those regarded as being prominent producers of the fruit or vegetable. Through mislabelling, which is another form of EMA, there is the potential to convince consumers they are buying juice from fruit or vegetables from a specific growing region when they are not.

An automated solution

Against this backdrop, beverage manufacturers, retailers and national authorities are seeking a reliable method of juice authentication that determines its exact constituents. This is increasingly important for regulatory compliance, consumer safety and confidence, and to protect the integrity and competitiveness of the juice market.

Advances in analytical technologies like nuclear magnetic resonance (NMR) spectroscopy are offering a new way to provide definitive proof of juice authenticity, enabling testing laboratories to identify multiple illicit modes of adulteration and production, quickly and reliably. 

Limitations of traditional QC

Traditional juice authenticity and quality control analysis can be time-consuming and involves various analytical instruments and methods. In Europe, juice products, including their quality, composition, production, and labelling, are governed by the European Fruit Juice Directive (Directive 2012/12/EU) as well as reference guidelines on quality, authenticity, and identity from the European Fruit Juice Association (AIJN) Code of Practice. The International Fruit and Vegetable Juice Association (IFU) recommends methods of analysis as well, which can be complex.

Because natural juice is characterised by specific mineral levels, elemental analysis can be applied based on element markers, using techniques such as inductively coupled plasma mass spectrometry (ICP-MS). This technique offers high accuracy and a low detection limit – but comes at a high cost. Sample pre-treatment is expensive and is a major drawback in this technique.

Chromatographic techniques enable authentication by determining specific marker compounds, offering both sensitivity and high separation efficiency. Here, too, however, sample preparation is complex, and chromatography also carries the risk of losing instable compounds. These targeted methods are also limited to the analysis of specific targets, meaning that anything outside of those parameters is not analysed.

Deoxyribonucleic acid (DNA)-based analytical methods, such as polymerase chain reaction (PCR), can be used to authenticate varieties by differentiating between the plant species within a fruit juice. However, these methods are complex, expensive to run, and become less reliable when the DNA profile of the juice sample degrades under thermal processing in acidic conditions.

The future is NMR

NMR spectroscopy is emerging as a powerful, definitive solution for fruit and vegetable juice authentication and is expected to be recommended imminently by the IFU.

NMR is an analytical technique that enables non-invasive, non-destructive and quantitative analysis of molecular structure, dynamic processes and chemical reactions. It delivers robust and simultaneous quantitative analysis of juice authentication parameters in an automated solution for rapid quality control. NMR provides a molecular fingerprint of a juice sample, giving definitive information about its composition and the presence of adulterants such as sugars and sweeteners. It is the ability to generate this unique fingerprint that means NMR can determine the fruit type, variety, product type (such as concentrate) and origin, and detect the illegal addition of other fruits or constituents.

The technique provides valuable insights with high confidence in the results through statistical comparison of NMR profiles to a reference library. NMR can also confirm the geographical origin of a juice sample based on its unique profile, by comparing it statistically to a large reference library of samples from around the world.

Fully automated workflow

The latest NMR systems provide a fully automated workflow from sample to report. They offer easy sample preparation and do not require the use of organic solvents, making them faster and cheaper to run than the alternative techniques. NMR enables detailed compositional analysis to be performed by non-experts, in less than 20 minutes.

In conventional analyses, different target parameters require their own methods. Sample preparation and analysis times can be long and complex. Quantitative 1H NMR can quantify all relevant parameters in the same analysis and, thanks to this multiparametric approach, masking adulteration is difficult. The technique’s high reproducibility allows precise sample matching and, once acquired, the data can be re-processed against a larger or updated reference database, even years later. 

A helping hand

The unique advantages of NMR spectroscopy make it well-placed to become the analytical method of choice for fast, effective juice authentication and quality control. This screening approach offers a rapid and cost-effective alternative to traditional methods of routine quality control.

Modern NMR systems and software packages offer routine, straightforward workflows, automatically analysing more than 60 samples in one run. NMR is set to become an indispensable tool in the fight against illegal adulteration of juice, having already proven its worth against similar practices in high-value branded food products such as honey, wine and olive oil production.

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