Toufic Rizk

Fungal contamination and Aflatoxin B1 and Ochratoxin A in Lebanese wine-grapes and musts

Five hundred and ten strains of filamentous fungi were isolated from Lebanese grapes during 2005 at veraison and harvesting periods. Four hundred eighty-seven isolates belonged to the Aspergillus spp. (95.5%) and 23 belonged to the Penicillium spp. (4.5%). Black aspergilli constituted 56.9% (52.2% Aspergillus niger aggregates, 2.9% Aspergillus japonicus and 1.8% Aspergillus carbonarius) while the isolation rate of Aspergillus flavus the none habitual member of grape mycobiota was 43.1% of the total Aspergillus spp. isolated. All isolates were tested for the ability to produce the Ochratoxin A (OTA) and the Aflatoxin B1 (AFB1). A. carbonarius showed that it is the only species able to produce the OTA with a production ability of 100% and a maximum concentration reaching 8.38microg/g CYA. As for the aflatoxigenic ability, 43.4% of A. flavus isolates produced this mycotoxin with a maximum production reaching 22.6microg/g CYA while none of the other isolates showed a production capacity of this mycotoxin. Forty-seven samples of must produced from the collected grapes were also analyzed. None of these samples was contaminated by OTA at a detectable limit while 40% of these same samples were found to contain AFB1 with concentrations ranging from 0.01 to 0.46microgl(-1).

Differentiation between Aspergillus flavus and Aspergillus parasiticus from pure culture and aflatoxin-contaminated grapes using PCR-RFLP analysis of aflR-aflJ intergenic spacer.

Aflatoxins (AFs) represent the most important single mycotoxin-related food safety problem in developed and developing countries as they have adverse effects on human and animal health. They are produced mainly by Aspergillus flavus and A. parasiticus. Both species have different aflatoxinogenic profile. In order to distinguish between A. flavus and A. parasiticus, gene-specific primers were designed to target the intergenic spacer (IGS) for the AF biosynthesis genes, aflJ and aflR. Polymerase chain reaction (PCR) products were subjected to restriction endonuclease analysis using BglII to look for restriction fragment length polymorphisms (RFLPs). Our result showed that both species displayed different PCR-based RFLP (PCR-RFLP) profile. PCR products from A. flavus cleaved into 3 fragments of 362, 210, and 102 bp. However, there is only one restriction site for this enzyme in the sequence of A. parasiticus that produced only 2 fragments of 363 and 311 bp. The method was successfully applied to contaminated grapes samples. This approach of differentiating these 2 species would be simpler, less costly, and quicker than conventional sequencing of PCR products and/or morphological identification.

Geoclimatic, morphological, and temporal effects on Lebanese olive oils composition and classification: A (1)H NMR metabolomic study.

Two hundred and thirty-four Lebanese olive samples were collected from different regions and the corresponding oils were analysed by (1)H NMR spectroscopy. The variables obtained, related to fatty acids and minor components, were used as inputs in univariate and multivariate analyses aiming to characterize and classify the oils according to geographical, morphological, and temporal factors. Samples were sorted according to the colour, size, and shape of olives, which allowed statistically significant classifications to be achieved. A sequential strategy was developed to discriminate among samples from different altitudes and latitudes. Following this strategy, obvious trends and classifications were obtained at subregional level. Furthermore, the shift in the harvest date within a range of three weeks was considered and its effect on the classification models was investigated. Likewise, the harvest year effect was evaluated; the precipitation level in April and May had a significant impact on the characteristics of the oils.

13C isotopomics of triacylglycerols using NMR with polarization transfer techniques

A rapid and very precise method is proposed to simultaneously determine the position-specific 13C content and the metabolomic profile of triacylglycerols (isotopomics). 13C-NMR spectra are obtained by using an adiabatic INEPT sequence; the experiment time is reduced by a factor of 7 with respect to a one-pulse acquisition.

A strategy for simultaneous determination of fatty acid composition, fatty acid position, and position-specific isotope contents in triacylglycerol matrices by 13C-NMR

AbstractTriacylglycerols, which are quasi-universal components of food matrices, consist of complex mixtures of molecules. Their site-specific 13C content, their fatty acid profile, and their position on the glycerol moiety may significantly vary with the geographical, botanical, or animal origin of the sample. Such variables are valuable tracers for food authentication issues. The main objective of this work was to develop a new method based on a rapid and precise 13C-NMR spectroscopy (using a polarization transfer technique) coupled with multivariate linear regression analyses in order to quantify the whole set of individual fatty acids within triacylglycerols. In this respect, olive oil samples were analyzed by means of both adiabatic 13C-INEPT sequence and gas chromatography (GC). For each fatty acid within the studied matrix and for squalene as well, a multivariate prediction model was constructed using the deconvoluted peak areas of 13C-INEPT spectra as predictors, and the data obtained by GC as response variables. This 13C-NMR-based strategy, tested on olive oil, could serve as an alternative to the gas chromatographic quantification of individual fatty acids in other matrices, while providing additional compositional and isotopic information. Graphical abstractA strategy based on the multivariate linear regression of variables obtained by a rapid 13C-NMR technique was developed for the quantification of individual fatty acids within triacylglycerol matrices. The conceived strategy was tested on olive oil.

Precise and rapid isotopomic analysis by (1)H-(13)C 2D NMR: Application to triacylglycerol matrices.

An optimized HSQC sequence was tested and applied to triacylglycerol matrices to determine their isotopic and metabolomic profiles. Spectral aliasing and non-uniform sampling approaches were used to decrease the experimental time and to improve the resolution, respectively. An excellent long-term repeatability of signal integrals was achieved enabling to perform isotopic measurements. Thirty-two commercial vegetable oils were analyzed by this methodology. The results show that this method can be used to classify oil samples according to their geographical and botanical origins.

A sharper characterization of the geographical origin of Lebanese wines by a new interpretation of the hydrogen isotope ratios of ethanol

The hydrogen isotope ratios of the methyl [(D/H)I] and methylene [(D/H)II] groups in ethanol can be used as geographical origin tracers of wines. These ratios reflect not only the deuterium content of sugars but also that of water in the grape medium, and hence are influenced by the irrigation, the degree of ripeness at harvest, and other viticultural and enological practices. Thus, the isotopic redistribution coefficients between water in the grape must and the methyl and methylene sites of ethanol were determined and then used to compute an isotopic ratio [(D/H)Is] representing the contribution of the fermentable sugars to (D/H)I. To evaluate the discrimination power of (D/H)Is, the ethanol D/H ratios of 78 Lebanese wine samples from different vineyards were determined using the SNIF-NMR method. An improved classification at the subregional level was obtained using (D/H)Is which exhibits an inverse linear correlation with the annual precipitation amount. Furthermore, the variations of the ethanol D/H ratios with the degree of grape ripeness and with the juice fractions obtained from the inner and peripheral pulps of the grape berries were studied on a small sample set. These factors should be considered when using the SNIF-NMR results to characterize the geographical origin of wines.

Calculation of the c(3)a percentage in high sulfur clinker.

The aim of this paper is to clarify the influence of the clinker SO3 on the amount of C3A. The calculation of the cement phases percentages is based on the research work, Calculation of the Compounds in Portland Cement, published by Bogue in 1929 .The usage of high sulphur fuels, industrial wastes, and tires changes completely the working condition of Bogue because the assumed phase compositions may change. The results prove that increasing the amount of SO3 in the low alkali clinker decreases the percentages of C3A due to the high incorporation of alumina in the clinker phases mainly C2S and C3S. The correlation is linear till the clinker SO3 reaches the 2%. Over that the influence of the clinker SO3 became undetectable. A new calculation method for the determination of the C3A in the high sulphur and low alkali clinker was proposed.

Phytochemical screening and antityrosinase activity of carvacrol, thymoquinone, and four essential oils of Lebanese plants

In our study, we aim to explore the ability of four essential oils (EO) of Lebanese plants to inhibit the tyrosinase activity and to correlate their efficiency level to their phytochemical compositions.

Olive oil characterization and classification by 13C NMR with a polarization transfer technique: A comparison with gas chromatography and 1H NMR

In a previous work, we optimized and used a fast adiabatic 13C-INEPT (Insensitive Nuclei Enhanced by Polarization Transfer) experiment for the isotopomic analysis of olive oil samples, which allowed us quantifying individual fatty acids within triacylglycerols through multivariate linear regression models. The goal of this study was to validate these models and to evaluate the power of 13C-INEPT in the authentication of olive oils relative to gas chromatography (GC) and 1H NMR. In this respect, a new set of olive oil samples was analyzed by these three techniques. The analytical variables thus obtained as well as their corresponding long-term repeatability were compared. As a result, the reliability of the fatty acid quantification models was proven and the best classification of olive oils according to the altitude of the olive grove and to the morphological aspect (color) of the olives was achieved by means of 13C-INEPT.