Effect of the addition of nitrate to milk on the formation of volatile N-nitrosamines and apparent total N-nitroso compounds

 Saint-Paulin, a French semihard cheese, was manufactured from milk with and without added NO₃ ^–. Reference and experimental cheeses were analysed at different stages of ripening for the presence of apparent total N-nitroso compounds (ATNC) by chemical denitrosation and chemiluminescence detection (thermal energy analyser). The fate of NO₃ ^– and NO₂ ^–was also scrutinized. The levels of ATNC and of volatile N-nitrosamines were followed during ripening. After 60 days of ripening, ATNC were detected at concentrations of 27 μg NO-N/kg and 64 μg NO-N/kg in the cheeses obtained from milk with and without added NO₃ ^–, respectively. The NO₃ ^– contents of both cheeses were nearly the same, and below 5 mg/kg. The occurrence of NO₂ ^–was not observed. No relationship was found between the NO₃ ^– contents and the contamination of the cheeses by volatile N-nitrosamines. At the beginning of ripening, the cheeses manufactured with added NO₃ ^- showed high levels of ATNC (mean value 5800 μg N-NO/kg with large variations of 570–15210 μg NO-N/kg). These ATNC contents rapidly decreased during the first days of ripening (96%), but decreased much more slowly during the following days. An hypothetical mechanism, attempting to explain the disappearance of ATNC, involving the formation of alkylated species in the cheese was proposed. Received: 30 March 1998 / Revised version: 7 October 1998     

Impact of volume fiber on distribution of thermal stress residual near fiber/epoxy interface using axisymmetric model

Thermal residual stresses are important in composite materials. The aim of this work is the computation of thermal residual stresses by finite element method and the effect of volume fraction on their distribution. In this work, two cases are considered by using an epoxy matrix with respectively glass and carbon fibers with a different volume fiber using an axisymmetric model. From the results of the numerical calculation, it is shown that the stresses are important and thus should be taken into account. The interface is affected by thermal stresses. The normal stresses and shear stress value have an influence on the behavior of the material. Hence, on the performance of composites during service, is an information of significance for the designers.     

Classification of Honey According to Geographical and Botanical Origins and Detection of Its Adulteration Using Voltammetric Electronic Tongue

Main possible honey fraud is the addition of various sugar syrups. But, there are also other types of fraud, such as deception on the geographical and/or botanical origin product. Providing a product of the hive with full authenticity is therefore crucial for the preservation of beekeeping. In this pursuit, voltammetric electronic tongue (VE-tongue) was employed to classify honey samples from different geographical and botanical origins. Furthermore, VE-tongue was used to detect adulterants such as glucose syrup (GS) and saccharose syrup (SS) in honey. The data obtained were analyzed by three-pattern recognition techniques: principal component analysis (PCA), support vector machines (SVMs), and hierarchical cluster analysis (HCA). These methods enabled the classification of 18 honeys of different geographical origins and 7 honeys of different botanical origins. Excellent results were obtained also in the detection of adulterated honey. Therefore, this simple method based on VE-tongue could be useful in the honey packaging and commercialization industry.     

On the reduce of interfacial shear stresses in fiber reinforced polymer plate retrofitted concrete beams

One major problem when using bonded fiber reinforced polymer (FRP) plate is the presence of high interfacial shear stresses near the end of the composite (edge effect) which might govern the failure of the strengthening schedule. It is known that the decrease of plate thickness reduces the magnitude of stress concentration at plate ends. Another way is to use a plate end tapering. In this paper, the analytical solution of interfacial shear stresses obtained has been extended by a numerical procedure using the modal analysis of finite element method (FEM) in a retrofitted concrete (RC) beam with the FRP plate with tapered end, which can significantly reduce the stress concentration. This approach allows taking into consideration the variation of elastic properties of adhesive and plate as well as the complicated geometrical configurations and effects of thermal loads.     

Application of a portable electronic nose system to assess the freshness of Moroccan sardines

In this paper, we propose the investigation and the realisation of an electronic nose system able to evaluate fish freshness in real-time, under the constraints of being suitable for miniaturization and portability. Six tin oxide based Taguchi gas sensors are used to analyse sardine samples stored at 4 °C. A dedicated real-time data acquisition system based on a microcontroller and portable computer have been designed and constructed for this application. Principal component analysis (PCA) and support vector machines (SVMs) results show that the system is able to assess the freshness of sardines stored at 4 °C.     

A Finite Element Analysis for Evaluation of J-Integral in Plates Made of Functionally Graded Materials with a Semicircular Notch

Journal of Failure Analysis and Prevention - This work introduces a numerical investigation using finite element method to evaluate the J-integral at crack tip in titanium boride...     

The Influence of the Incorporation Method and Mass Ratio of Copper on the Antibacterial Activity of MCM-41

Silicon - This work deals with the use for the first time of waste spent glass as a new source of silicon and aluminum in the synthesis of highly ordered MCM-41 nanomaterials and also treats the...     

Precautions to be taken in the analysis of total N-nitroso compounds

Methodologies used to assess N-nitroso compounds as a group by chemical denitrosation with hydrogen bromide in glacial acetic acid have been described. Carrying out these analyses without precautions can cause considerable variations in results. Some pitfalls must be avoided in order to obtain valuable results and accurate interpretations.