Fast and Accurate Determination of Minute Ochratoxin A Levels in Cereal Flours and Wine with the Label-Free White Light Reflectance Spectroscopy Biosensing Platform.

Ochratoxin A (OTA) is one of the most toxic naturally encountered contaminants and is found in a variety of foods and beverages, including cereals and wine. Driven by the strict regulations regarding the maximum allowable OTA concentration in foodstuff and the necessity for on-site determination, the development of fast and sensitive methods for the OTA determination in cereal flours and wine samples, based on white light reflectance spectroscopy, is presented. The method relied on appropriately engineered silicon chips, on top of which an OTA-protein conjugate was immobilized. A polyclonal antibody against OTA was then employed to detect the analyte in the framework of a competitive immunoassay; followed by the subsequent addition of a biotinylated secondary antibody and streptavidin for signal enhancement. A small size instrument performed all assay steps automatically and the bioreactions were monitored in real time as the software converted the spectral shifts into effective biomolecular adlayer thickness increase. The assay developed had a detection limit of 0.03 ng/mL and a working range up to 200 ng/mL. The assay lasted 25 min (less than 1h, including calibrators/antibody pre-incubation) and was accomplished following a simple sample preparation protocol. The method was applied to corn and wheat flour samples and white and red wines with recovery values ranging from 87.2 to 111%. The simplicity of the overall assay protocol and convenient instrumentation demonstrates the potential of the immunosensor developed for OTA detection at the point of need.

Risk of allergic reactions to wine, in milk, egg and fish-allergic patients.

BACKGROUND: European legislators and wine producers still debate on the requirement for labeling of wines fined with potentially allergenic food proteins (casein, egg white or fish-derived isinglass). We investigated whether wines fined with known concentrations of these proteins have the potential to provoke clinical allergic reactions in relevant patients. METHODS: In-house wines were produced for the study, fined with different concentrations of casein (n = 7), egg albumin (n = 1) and isinglass (n = 3). ELISA and PCR kits specific for the respective proteins were used to identify the fining agents. Skin prick tests and basophil activation tests were performed in patients with confirmed IgE-mediated relevant food allergies (n = 24). A wine consumption questionnaire and detailed history on possible reactions to wine was obtained in a multinational cohort of milk, egg or fish allergic patients (n = 53) and patients allergic to irrelevant foods as controls (n = 13). RESULTS: Fining agents were not detectable in wines with the available laboratory methods. Nevertheless, positive skin prick test reactions and basophil activation to the relevant wines were observed in the majority of patients with allergy to milk, egg or fish, correlating with the concentration of the fining agent. Among patients consuming wine, reported reactions were few and mild and similar with the ones reported from the control group. CONCLUSION: Casein, isinglass or egg, remaining in traces in wine after fining, present a very low risk for the respective food allergic consumers. Physician and patient awareness campaigns may be more suitable than generalized labeling to address this issue, as the latter may have negative impact on both non-allergic and allergic consumers.

Comparison of analytical methodologies based on 1h and 31p NMR spectroscopy with conventional methods of analysis for the determination of some olive oil constituents.

The present study was designed to assess the agreement between analytical methodologies based on 1H and 31P NMR spectroscopy and conventional analytical methods (titration, gas chromatography, and high performance liquid chromatography) for measuring certain minor and major constituents (free acidity, fatty acids, iodine value, and phenolic compounds) of olive oil. The standard deviations of the NMR method were comparable to those of the conventional methods, except perhaps those of the total hydroxytyrosol and total tyrosol. Linear regression analyses showed strong correlations between NMR and conventional methods for free acidity, total hydroxytyrosol, total tyrosol, total diacylglycerols, (+)-pinoresinol, (+)-1-acetoxypinoresinol, and apigenin; good correlations for linoleic acid, free hydroxytyrosol, and free tyrosol; and weak correlations for oleic acid, linolenic acid, saturated fatty acids, and luteolin. Furthermore, a method comparison study was conducted and the agreement between NMR and conventional methods was evaluated by using the Bland and Altman statistical analysis. The distribution of the data points in the bias plot showed that 96.4% and 100% of the measurements of free acidity and iodine value, respectively, were within the limits of agreement of the two methods. For the remaining constituents of olive oil, the percentage of measurements, located within the limits of agreement, ranged from 94% to 98.5%.

Detection of extra virgin olive oil adulteration with lampante olive oil and refined olive oil using nuclear magnetic resonance spectroscopy and multivariate statistical analysis.

High-field 31P NMR (202.2 MHz) spectroscopy was applied to the analysis of 59 samples from three grades of olive oils, 34 extra virgin olive oils from various regions of Greece, and from different olive varieties, namely, 13 samples of refined olive oils and 12 samples of lampante olive oils. Classification of the three grades of olive oils was achieved by two multivariate statistical methods applied to five variables, the latter being determined upon analysis of the respective 31P NMR spectra and selected on the basis of one-way ANOVA. The hierarchical clustering statistical procedure was able to classify in a satisfactory manner the three olive oil groups. Subsequent application of discriminant analysis to the five selected variables of oils allowed the grouping of 59 samples according to their quality with no error. Different artificial mixtures of extra virgin olive oil-refined olive oil and extra virgin olive oil-lampante olive oil were prepared and analyzed by 31P NMR spectroscopy. Subsequent discriminant analysis of the data allowed detection of extra virgin olive oil adulteration as low as 5% w/w for refined and lampante olive oils. Further application of the classification/prediction model allowed the estimation of the percent concentration of refined olive oil in six commercial blended olive oils composed of refined and virgin olive oils purchased from supermarkets.