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Traditional cheeses, with protected names (PDO/PGI) are sold at a premium and hence can be susceptible to substitution and fraud. This review reports the available authentication methods, either chemical, physical, or DNA-based methods, currently used for origin authentication, highlighting their principle, reported application to cheese geographical origin authentication, performance, and respective advantages and limits. Isotope and elemental fingerprinting showed consistent accuracy in origin authentication. Other chemical and physical methods, such as near-infrared spectroscopy and NMR, require more studies and larger sampling to assess their discriminative power. Emerging DNA-based methods, such as metabarcoding, showed good potential for origin authentication. However, metagenomics, providing a more in-depth view of the cheese microbiota (up to the strain level) is an interesting approach to authenticate the origin of cheeses, but is still in its early development.

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Herbs and spices are one of the food commodities most susceptible to adulteration and fraud. In this study, 5 fingerprinting techniques - Near Infrared (NIR), Mid-Infrared (MIR), Hyper Spectral Imaging (HSI), Gas Chromatography coupled to Mass Spectrometry (GC–MS), and Proton-transfer Reaction Time-of-Flight Mass spectrometry (PTR-TOF-MS), combined with chemometrics, are examined to evaluate their potential to authenticate oregano. In total, 102 oregano samples from one harvest season were analysed for origin and variety assessment, 159 samples for adulteration assessment, and 72 samples for batch-to-batch control. Different chemometric models were applied for adulteration, origin and variety assessment. The best results were for origin assessment, which gave prediction rates of more than 89%. A level of 10% adulteration of oregano with myrtle, sumac, olive and cistus could be detected using HSI, NIR and PTR-TOF-MS.

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Dairy products (milk, butter, cheese, yoghurt etc) form an important part of the diet, and are a significant part of national and international trade of most countries. This review by Brazilian researchers outlines the frequent forms of food fraud in dairy products and the application of traditional techniques for their detection, highlighting the gaps and disadvantages of these techniques. It then describes the application of NIR (near-infrared) spectroscopy and HSI (hyperspectral imaging) for the detection of food fraud mainly in cheese, butter, and yogurt. In conclusion, NIR spectroscopy and HSI are rapid non-destructive techniques, which also require chemometric models for their interpretation, but have been successfully applied to the authentication of dairy products.

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This review investigates the feasibility of different non-destructive techniques used for authenticating meat products, which could provide real-time monitoring in the near future. The spectroscopic techniques reviewed are NIR (near infrared), MIR (mid-infrared), FTIR (Fourier transform infrared), and Raman. The imaging techniques discussed are colour imaging, hyperspectral imaging and Xray imaging with computed technology. The advantages of these techniques is that they can be applied in-situ, and they give rapid results, but calibration procedures are laborious. In addition, the results are influenced by scanning times, sample to detector distance and environmental factors such as ambient temperature, humidity, illumination conditions, and sample temperature, the latter can differ in meat processing facilities. However, it is hoped that the application of these techniques will be easier with the improvement in instrumental technology, the availability of high-speed computers with appropriate storage capacity, and the development of appropriate chemometric procedures.

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Maple syrup, the concentrated sap of Acer saccharum March, is sought after for its unique flavour and taste. As a popular and high value product, it is increasingly susceptible to adulteration by other sugar syrups. This review looks at most recent advances in the analytical methods used for detecting the different types of maple syrup adulteration.It concludes that SpectrAcer and nuclear magnetic resonance (NMR) are the most efficient methods for detection of maple syrup adulteration. SpectrAcer, an automated spectroscopy sytem developed by the Canadian company Acer, based reflected light at different wavelengths using the syrup's fluorescence properties with UV, and sugar composition at other wavelengths.

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Garlic is widely used in cooking all over the world. Researchers at Queens University Belfast have verified whether NIR (near infrared) and FTIR (Fourier transform infrared) spectroscopy with chemometric analysis can detect garlic mixed with possible adulterants. Authentic and adulterated garlic (with talc, maltodextrin, corn starch, cornflour, peanut butter powder, sodium caseinate, potato starch, rice flour, cassava and white maize meal) samples were prepared at 20–90% levels, and NIR and FTIR spectra of the samples obtained. Principal component analysis (PCA) models were created to establish if there was separation of garlic from the adulterants.Orthogonal partial least squares – discriminant analysis (OPLS-DA) models were then developed to be able to detect and classify the levels of adulteration correctly using both NIR and FTIR.

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This study compared the capabilities of three spectroscopic techniques as fast screening platforms for honey authentication purposes. Multifloral honeys were collected in the three main honey-producing regions of Argentina over four harvesting seasons to give a total of 502 samples. Spectra were run on each of the samples with FT-MIR ( Fourier transform mid-infrared), NIR (near infrared) and FT-Raman  (Fourier transform Raman)  spectroscopy. The spectroscopic platforms were compared on the basis of the classification performance achieved under a supervised chemometric approach. Very good classification scores to distinguish the three Argentian regions were achieved by all the spectroscopies, and a nearly perfect classification was provided by FT-MIR. The results obtained in the present work suggested that FT-MIR had the best potential for fingerprinting-based honey authentication, and demonstrated that sufficient accuracy levels to be commercially useful can be reached.

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Small amounts of low cost carob flour do not change the colour, aroma or taste characteristics of cocoa powder. Therefore, Spanish researchers have developed a NIR (near infra-red) method combined with chemometrics to determine that adulteration with carob flour has  taken place, and the amount of carob flour that has been used. Data sets using cocoa powders with different alkalisation levels, carob flours with three different roasting degrees, and adulterated samples prepared by blending cocoa powders with carob flour at several proportions, were obtained. For qualitative results, a principal component analysis (PCA) and a partial least squares discriminant analysis (PLS-DA) were used, giving a 100% classification accuracy to distinguish pure cocoa powders from adulterated samples. For quantitative analysis, a partial least squares (PLS) regression analysis was performed giving a root mean square error of prediction of 3.2%, thus making the method fit for purpose for determining the amount of carob flour in cocoa powder within this error.

              Read the abstract at: cocoa powder adulteration with carob flour

Chinese researchers have developed an integrated approach combining HPLC/DAD, GC/MS, near infrared (NIR) spectroscopy, and chemometrics  to geographically discriminate saffron samples from Iran and China. Using a dataset based on 98 samples of saffron, the saffron compounds picrocrocin and two types of crocins were found to be the discriminating markers, and the Chinese samples had higher contents of safranal and picrocrocin but lower cis-crocin 3Gg, kaempferol-3-O-sophoroside and isophorone. 

 Furthermore, an NIR method was successfully established to rapidly distinguish the Chinese and Iranian samples. The relationship between an ISO standard and the contents of the chemical indices was also studied. The results indicated that the ISO standard should be revised, especially for analysing safranal.

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This article looks at the application of certain spectroscopic techniques to determine the presence of adulterants in food ingredients and products. Applications cited include the detection of melamine in baby formula, saffron and ginger authenticity, and the detection of substitutes in beef mince.

Read the article at: spectroscopic techniques fight food fraud