交叉羰基还原偶联法合成二茂铁基二芳基乙烯衍生物

通过低价钛引起的交叉羰基的偶联合成了二茂铁基二芳基乙烯衍生物,原料廉价易得,合成步骤简便,产率达７４％。     

Estimation of the bio-accessible fraction of Cr,As, Cd and Pb in locally available bread using on-line continuous leaching method coupled to inductively coupled plasma mass spectrometry

A previously developed, efficient and simple on-line leaching method was used to assess the maximum bio-accessible fraction (assuming no synergistic effect from other food and beverage) of potentially toxic elements (Cr, As, Cd and Pb) in whole wheat brown and white bread samples. Artificial saliva, gastric juice and intestinal juice were successively pumped into a mini-column, packed with bread (maintained at 37 °C) connected on-line to the nebulizer of an inductively coupled plasma mass spectrometry (ICP-MS) instrument equipped with a collision-reaction interface (CRI) using hydrogen as reaction gas to minimize carbon- and chlorine-based polyatomic interferences. In contrast to the conventional batch method to which it was compared, this approach provides real-time monitoring of potentially toxic elements that are continuously released during leaching. Mass balance for both methods was verified at the 95% confidence level. Results obtained from the whole wheat brown and white bread showed that the majority of Cr, Cd and Pb was leached by gastric juice but, in contrast, the majority of As was leached by saliva. While there was higher total content for elements in whole wheat bread than in white bread, a higher percentage of elements were bio-accessible in white bread than in whole wheat bread. Both the on-line and batch methods indicate that 40–98% of toxic elements in bread samples are bio-accessible. While comparison of total analyte concentrations with provisional tolerable daily intake values may indicate some serious health concern for children, when accounting for the bio-accessibility of these elements, bread consumption is found to be safe for all ages.     

Modelling the biaxial elongational deformation of soft solids

This paper reports the results of modelling the biaxial extension of soft solids in lubricated squeezing flow geometry. The nonlinear constitutive model including the single mode Phan-Thien Tanner (PTT) model has been used to model the behaviour of different materials such as a soft tissue (pig liver) and three wheat flours with different protein contents. These were used to evaluate the usefulness of the method and to establish how different compositional or structural parameters could be relevant in determining the rheological behaviour of soft solids. From this study it was found that homogeneous uniaxial compression can be achieved in lubricated squeezing flow. Modelling results are in good agreement with experimental results for all the materials considered.     

First screening method for the simultaneous detection of seven allergens by liquid chromatography mass spectrometry

The development of a multi-method for the detection of seven allergens based on liquid chromatography and triple-quadrupole tandem mass spectrometry in multiple reaction mode is described. It is based on extraction of the allergenic proteins from a food matrix, followed by enzymatic digestion with trypsin. The chosen marker peptides were implemented into one method that is capable of the simultaneous detection of milk, egg, soy, hazelnut, peanut, walnut and almond. This method has been used to detect all seven allergenic commodities from incurred reference bread material, which was baked according to a standard recipe from the baking industry. Detected concentrations ranged from 10 to 1000 μg/g, demonstrating that the mass spectrometric based method is a useful tool for allergen screening.     

Multiple headspace solid-phase microextraction after matrix modification for avoiding matrix effect in the determination of ethyl carbamate in bread

This study presents the potential of multiple headspace solid-phase microextraction (multiple HS-SPME) for the quantification of analytes in solid samples. Multiple HS-SPME shares the same advantages as SPME. It also enables a complete recovery of the target compound and therefore the matrix effect, which commonly appears in SPME-based analysis, is avoided. A method based on multiple HS-SPME for the determination of the toxic contaminant ethyl carbamate (EC) in bread samples has been developed and validated, using gas chromatography with flame ionization detector. A novel polyethylene glycol/hydroxy-terminated silicone oil fiber was prepared for the first time and subsequently used instead of commercial ones because of its high extraction ability and good operational stability. An important problem still remained in multiple HS-SPME of EC in fresh bread samples. The adsorption of EC by water in the samples caused low transport of analyte to the headspace, which made multiple HS-SPME invalidated. Mixing with anhydrous sodium sulphate, the sensitivity of the method was improved and the problem was solved. The proposed method showed satisfactory linearity (0.15–1500 μg g⁻¹), precision (1.6%, n = 5) and limit of detection (0.041 μg g⁻¹). Good recoveries, from 92.5 to 103.4%, were observed at three spiking levels. The method was applied to 14 bread samples. The multiple HS-SPME technique offers several advantages including reducing the manipulation time and cost, and avoiding analyte losses, especially in the analysis of a large number of samples in different matrices.     

Occurrence of ochratoxin A in bread consumed in Morocco

One hundred samples of commercial bread purchased from January to October (2006) from retail bakeshops in five different cities (Rabat, Témara, Salé, Casablanca and Meknès) in Morocco were surveyed for the presence of ochratoxin A (OTA) using liquid chromatography coupled to fluorescence detection. The identification of OTA in positive bread samples was confirmed by methyl ester derivatization. Analytical results showed that forty eight (48%) samples were positive with OTA greater than the limit of quantification (LOQ = 0.051 ng/g). Levels of OTA in positive samples ranged between 0.14 and 149 ng/g. The average contamination of bread samples with OTA was 13 ± 1.5 ng/g. The highest frequency of positive samples (61.5%) and the most contaminated sample (149 ng/g) were found in bread commercialized in the Casablanca area. Twenty six of the positive samples exceeded the maximum level of 3 ng/g set by European regulations for OTA in cereals and derivatives. Based in the results presented in this study, the estimated daily intake of OTA from bread was 126 ng/kg bw/day. The present paper is the first ever drafted on the natural occurrence of OTA in bread consumed in Morocco. Data on the daily intake of OTA by the Moroccan population are also estimated for the first time.     

Ultrasound treated potato peel and sweet lime pomace based biopolymer film development

Treatment and management of food processing waste is a major challenge for food industry. Potato processing industry generates tremendous amount of peel and consider it as zero valued waste. Again, pomace generated after juice extraction from sweet lime pulp is considered as waste and not properly utilized. Whereas these waste could be utilized for the development of biodegradable packaging film to overcome environmental issues. Composite films were prepared with varying proportion of potato peel powder (PP) and sweet lime pomace (SLP) in the ratio of 0:1(A), 0.5:1(B), 1:1(C), 1:0.5(D), 1:0(E) with an ultrasound treatment of 45 min, and 0:1(F), 0.5:1(G), 1:1(H), 1:0.5(I), 1:0(J) with an ultrasound treatment of 60 min. Ultrasound was applied for 45 and 60 min to film forming solutions to break down biopolymer particles small enough to form a film. All the films were analyzed for their barrier and mechanical properties. It was observed that increasing ultrasound treatment times gives better result in film properties and less PP content also gives better film properties, from these observations film G prepared with 0.5:1 (PP:SLP) showed better characteristics among all other films. Water vapor permeability, moisture absorption, water solubility, breakage strength and elongation capacity of G film were reported as 7.25 × 10⁻⁹ g/Pa h m, 12.88 ± 0.348%, 38.92 ± 0.702%, 242.01 ± 3.074 g and 7.61 ± 0.824 mm respectively. However, thermal decomposition for film G took place above 200 °C. The film forming solution of selected G film, added with clove essential oil (1.5%) as an antimicrobial agent was wrapped on bread and stored it for 5 days. The film was successful in lowering the weight loss, reducing the hardness and inhibition of surface microbial load from bread sample.     

微波消解-全谱直读等离子体发射光谱法测定面包改良剂中总溴的研究

采用微波消解样品、全谱直读等离子体发射光谱法(ICP—AES)测定面包改良剂中的溴含量。通过试验,优化了微波消解的条件和仪器的最佳工作参数：154．065nm波长处溴的检出限为0．015mg／L(3δ),线性范围为0．05～100mg／L,样品分析结果的相对标准偏差小于5％(n=7),加标回收率在93％～105％之间,样品分析结果与分光光度法相一致．该法简便、快速、灵敏、准确、线性范围宽。     

The difference in a problem of rations from the Rhind mathematical papyrus

In an ancient Egyptian problem of bread distribution from the Rhind mathematical papyrus (dated between 1794 and 1550 B.C.), a procedure of “false position” is used in the calculation of a series of five rations. The algorithm is only partially illustrated in the problem text, and last century's prevailing interpretations suggested a determination of the series by trial and error. The missing part of the computational procedure is reconstructed in this article as an application of the algorithm, exemplified in the preceding section of the papyrus, to calculate an unknown quantity by means of the method of “false position.”     

Evaluation of bread firmness by Instron compression tests

The force-compression behaviour of three types of bread has been studied with an Instron machine at crosshead speeds of 25, 50 and 100 cm min^–1. Agreement with sensory evaluation of firmness, either in the mouth or by squeezing samples between the fingers, was achieved only at 100 cm min^–1 and with a compression of at least 50%. Part of the applied force appears to be used to overcome surface friction effects.This paper is based on the dissertation submitted by one of the authors (A.M.A.S.) in partial fulfilment of the requirements for the degree of M. Sc. in Food and Management Science of the University of London.