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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

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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

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