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60 MHz proton NMR spectroscopy was used to analyse extracts from saffron spice and a range of potential adulterants and mixtures. Using a simple extraction procedure, good quality spectra were obtained which contain peaks from the characteristic metabolites picrocrocin and crocins, fatty acids and kaempferol. The spectra of samples from trusted suppliers were used to train one-class classification models by SIMCA, nearest neighbour and isolation forest methods. Applying these to spectra of saffron samples purchased from the online marketplace, it was found that 7 out of 33 samples were highly anomalous. From comparison with the spectra of known mixtures and confirmatory spectral analysis using 600 MHz NMR, it is probable that these contain considerable amounts of undisclosed foreign matter.

Cold pressed rapeseed oil (CPRO) is a relatively recent development in rapeseed processing, which produces a quality product with a high market value. High field NMR (400 MHz) is a well-established tool in food analysis, while low-field NMR (60 MHz) is much less studied. This study aims to establish the effectiveness of both techniques in identifying binary adulteration in CPRO. Three adulteration scenarios were investigated: a) CPRO and refined rapeseed oil (RRO); b) CPRO and refined sunflower oil (RSO); and c) CPRO and RRO or RSO. A range of classification techniques were trialled as well as partial least squares regression to gauge predictive quantification performance. The 400 MHz NMR achieved classification rates of 100% in the scenarios with a single adulterant, and 93% in the multiple adulterant scenario. The 60 MHz NMR produced lower but still encouraging classification rates (RSO 92%; RRO 85%; both RRO and RSO 87%).

Low field (60 MHz) 1H NMR spectroscopy was used to analyse a large (n = 410) collection of edible oils, including olive and argan, in an authenticity screening scenario. Experimental work was carried out on multiple spectrometers at two different laboratories, aiming to explore multivariate model stability and transfer between instruments. Three modelling methods were employed: Partial Least Squares Discriminant Analysis, Random Forests, and a One Class Classification approach. Clear inter-instrument differences were observed between replicated data collections, sufficient to compromise effective transfer of models based on raw data between instruments. As mitigations to this issue, various data pre-treatments were investigated: Piecewise Direct Standardisation, Standard Normal Variates, and Rank Transformation. Datasets comprised both phase corrected and magnitude spectra, and it was found that that the latter spectral form may offer some advantages in the context of pattern recognition and classification modelling, particularly when used in combination with the Rank Transformation pre-treatment.

Highlights • Lipophilic extracts of ground roast Arabica coffees were authenticated by benchtop NMR. • Small amounts of esterified 16-O-methylcafestol were found in Arabica coffees. • The compound identity was confirmed by NMR and MS experiments. • 16-OMC remains a useful marker for non-Arabicas as these contain much higher amounts. • 6 out of 60 retail Arabicas contained significant amounts of non-Arabica species., High-field and low-field proton NMR spectroscopy were used to analyse lipophilic extracts from ground roast coffees. Using a sample preparation method that produced concentrated extracts, a small marker peak at 3.16 ppm was observed in 30 Arabica coffees of assured origin. This signal has previously been believed absent from Arabicas, and has been used as a marker for detecting adulteration with robusta. Via 2D 600 MHz NMR and LC-MS, 16-O-methylcafestol and 16-O-methylkahweol were detected for the first time in Arabica roast coffee and shown to be responsible for the marker peak. Using low-field NMR, robusta in Arabica could be detected at levels of the order of 1–2% w/w. A surveillance study of retail purchased “100% Arabica” coffees found that 6 out of 60 samples displayed the 3.16 ppm marker signal to a degree commensurate with adulteration at levels of 3–30% w/w.

Flavan-3-ols and methylxanthines have potential beneficial effects on human health including reducing cardiovascular risk. We performed a randomized controlled crossover intervention trial to assess the acute effects of consumption of flavan-3-ol-enriched dark chocolate, compared with standard dark chocolate and white chocolate, on the human metabolome. We assessed the metabolome in urine and blood plasma samples collected before and at 2 and 6 h after consumption of chocolates in 42 healthy volunteers using a nontargeted metabolomics approach. Plasma samples were assessed and showed differentiation between time points with no further separation among the three chocolate treatments. Multivariate statistics applied to urine samples could readily separate the postprandial time points and distinguish between the treatments. Most of the markers responsible for the multivariate discrimination between the chocolates were of dietary origin. Interestingly, small but significant level changes were also observed for a subset of endogenous metabolites. H-1 NMR revealed that flavan-3-ol-enriched dark chocolate and standard dark chocolate reduced urinary levels of creatinine, lactate, some amino acids, and related degradation products and increased the levels of pyruvate and 4-hydroxyphenylacetate, a phenolic compound of bacterial origin. This study demonstrates that an acute chocolate intervention can significantly affect human metabolism.

We address the detection and quantitation of bovine milk in ‘buffalo’ mozzarella cheese using multiple reaction monitoring (MRM) mass spectrometry (MS). Focussing on the abundant protein α s1 -casein, present in both species but with 10 amino acid sequence differences, we extract a list of marker peptides specific to each species. ‘Identical’ peptides, exactly the same in both species, are used for relative quantitation of α s1 -casein in each milk type, whereas ‘similar’ peptides, present in both species but differing typically by one amino acid, are used to demonstrate relative quantitation in binary cheese mixtures. In addition, we report a pilot survey of UK supermarket and restaurant products labelled as ‘buffalo mozzarella’, finding that 2/3 of restaurant meals and supermarket pizzas are either mislabelled or adulterated.

Graphical abstract, Highlights • A new screening method for identifying the species in ground roast coffees using low-field NMR spectroscopy. • A calibration-free statistical approach to detecting adulteration of arabica with robusta coffee. • A study of time-varying spectral changes in the 16-OMC component of lipophilic extracts following sample preparation., This work reports a new screening protocol for addressing issues of coffee authenticity using low-field (60 MHz) bench-top 1H NMR spectroscopy. Using a simple chloroform-based extraction, useful spectra were obtained from the lipophilic fraction of ground roast coffees. It was found that 16-O-methylcafestol (16-OMC, a recognized marker compound for robusta beans) gives rise to an isolated peak in the 60 MHz spectrum, which can be used as an indicator of the presence of robusta beans in the sample. A total of 81 extracts from authenticated coffees and mixtures were analysed, from which the detection limit of robusta in arabica was estimated to be between 10% and 20% w/w. Using the established protocol, a surveillance exercise was conducted of 27 retail samples of ground roast coffees which were labelled as “100% arabica”. None were found to contain undeclared robusta content above the estimated detection limit.

peer-reviewed A Visible/Near-infrared (Vis/NIR) spectrometer equipped with a fibre-optic probe was used to stimulate and measure chlorophyll production in potato tubers, at low levels that produce no visible greening in the skin. Subtle responses to changes in the light stimulus were also tracked. When used with a static experimental setup, these measurements are precise. However, the technique is very sensitive to the exact geometry of the tuber-probe arrangement, and careful positioning of the probe is crucial. Complementary studies established that tissue under the apical buds (‘eyes’) has greater capacity to produce chlorophyll than other locations on the tuber surface. A long-term study of multiple tubers suggested that different cultivars behave differently in terms of the rate of chlorophyll production. These behavioural differences may be related to the batch dormancy status; validating this potential relationship is the focus of ongoing work.

Electromyography (EMG) of the masticatory muscles was compared with puncture testing and sensory evaluation, in a study of the textural properties of Red Delicious apples. An aim of the work was to use EMG in predictive models of sensory mealiness, as this property is strongly negatively associated with apple acceptability. It was found that subjects’ EMG sensitivity and repeatability are as good as, and frequently better, than their sensory sensitivity and reliability. In addition to systematic effects associated with data recording session and subject, EMG data was also systematically affected by subjects’ behavioural changes, specifically, the sensory evaluation being undertaken. Once these unwanted sources of variance were removed using suitable data pre-treatment, frequency-domain EMG data were correlated with puncture test data, and a significant relationship obtained for six out of thirteen subjects. For five out of these six subjects, the strength of this relationship was improved by making use only of higher frequencies (>15 Hz) in the EMG spectrum. EMG and puncture test data were each correlated with the sensory data. The nature of these relationships, in which the EMG frequency dependence effect was also clearly exhibited, demonstrated substantial common information content between the techniques. Finally, EMG and puncture test data were collectively used to model sensory mealiness, using univariate, bivariate and stepwise regression. Highly significant models were obtained for all but one subject’s sensory mealiness scores. In most cases, the best models used combinations of puncture test and EMG data from up to two of the four available electrodes.

It is desirable to monitor the quality of fresh fruit and vegetables since it benefits both producers, by offering a competitive advantage, and consumers, by improving consistency and hence encouraging a more healthy and varied diet. Near-infrared (NIR) spectroscopy is a candidate technology for monitoring agricultural produce quality. Here there has been a recent trend toward transmission-based geometries which interrogates deeper into the sample. NIR tomography is the natural progression of this, offering the possibility of detecting internal defects. The aim of this study was to evaluate a NIR tomograph built from relatively low-cost components. This comprised a stabilised VIS/NIR broadband source; a diode-array NIR spectrometer and a sample turntable. The angular positions of the detector and turntable could be moved independently of each other using two stepper motors under computer control. An experimental approach was adopted to generate a linear ‘difference image’ reconstruction matrix using 47 mm diameter potato cores, with a nominal length of 65 mm, and a 10 mm diameter black rod acting as an internal absorbing perturbation. The reconstruction matrix was generated for a single wavelength (689 nm) using multiple linear regression and evaluated for the case of two perturbing rods. The reconstructed image was of comparable quality to that typically obtained from other so-called ‘soft-field’ tomographic techniques. Although conducted under highly simplified conditions, the results suggest NIR tomography has potential for monitoring internal defects in agricultural produce.