HPLC determination of ochratoxin A in high consumption Tunisian foods

Samples (180) of high consumption food commodities from various regions of Tunisia were analysed to determine ochratoxin A contamination levels. A high performance liquid chromatography method for ochratoxin A determination was optimized. Samples were extracted with acetonitrile/water (80:20, v/v) solution and purified by immunoaffinity column. Average recoveries at 0.5 and 2 ng/g levels ranged from 84 ± 3.1 to 94 ± 1.2% with a between-day coefficient of variation (RSDR) of 3.8%. The method detection limit was 0.1 ng/g and ochratoxin identity was confirmed by methyl ester formation. The whole procedure was simple and fast if compared with other existing procedures. Performed analysis indicates that 45% of monitored samples were contaminated with levels ranging from 0.11 to 33.9 ng/g. The most contaminated commodities were barley, sorghum and wheat.     

Evolution of ochratoxin A content during red and rose vinification

BACKGROUND: This work aims to investigate the effects of the common vinification steps on the fate of the ochratoxin A (OTA) during wine making. Two assays of red and rose microvinification, with artificially contaminated grapes, were performed. The content of this mycotoxin was also monitored throughout the process of red wine making from naturally contaminated grapes in a winery. RESULTS: The results from the different assays revealed that the maceration of pomace have a significant effect on the increase of OTA content in red wine (P < 0.05) whereas the alcoholic fermentation had a reducing effect. However, the spontaneous malolactic fermentation showed no significant effect on the OTA content in wine (P > 0.05). Storage of red wine in tanks followed by draining caused a significant decrease of OTA of about 55%. Clarification with a gelatin oenological fining agent contributed to the removal of up to 58% of OTA from red wine. CONCLUSION: Overall, a consistent decrease in OTA concentration was noticed throughout either red or rose vinification. This work has contributed to the understanding of the fate of OTA during different vinification processes, especially from naturally contaminated grapes. Copyright © 2008 Society of Chemical Industry     

Oxidation of mercaptans in light oil sweetening by cobalt(II) phthalocyanine–hydrotalcite catalysts

Three Mg–Al hydrotalcites containing cobalt(II) phthalocyanine were prepared by direct synthesis, anion exchange and structure reconstruction. Differences in physicochemical properties and mechanical resistance were observed. The results of the mercaptan oxidation reaction were compared to those obtained with an industrial non-basic impregnated active charcoal. An important activity difference in favor of the prepared catalysts was obtained, confirming that the adequate tuning of basic and oxidant properties lead to a promising catalyst.     

3D Deformable Super-Resolution for Multi-Camera 3D Face Scanning

Low-cost and high-accuracy 3D face measurement is becoming increasingly important in many computer vision applications including face recognition, facial animation, games, orthodontics and aesthetic surgery. In most cases fringe projection based systems are used to overcome the relatively uniform appearance of skin. These systems employ a structured light camera/projector device and require explicit user cooperation and controlled lighting conditions. In this paper, we propose a 3D acquisition solution with a 3D space-time non-rigid super-resolution capability, using three calibrated cameras coupled with a non calibrated projector device, which is particularly suited to 3D face scanning, i.e. rapid, easily movable and robust to ambient lighting variation. The proposed solution is a hybrid stereovision and phase-shifting approach, using two shifted patterns and a texture image, which not only takes advantage of stereovision and structured light, but also overcomes their weaknesses. The super-resolution scheme involves a shape+texture 3D non-rigid registration for 3D artifacts correction in the presence of small non-rigid deformations as facial expressions.     

Robustness of adaptive control of robots

In this paper we discuss the robustness of adaptive control of rigid robots and methods for improving robustness in the face of unmodeled dynamics and external disturbances. Robustness to unmodeled dynamics is achieved using a so-called composite control strategy based on a singular perturbation formulation of the manipulator dynamics together with -modificiation. Rigorous stability proofs are given using a composite Lyapunov function approach.Research partially supported by the National Science Foundation under Grants INT-8902476 and MSM-9100618 and by the University of Illinois Manufacturing Research Center.     

Incidence of aflatoxins, ochratoxin A and zearalenone in tunisian foods

A total of 209 samples of different groups of foods widely consumed by the Tunisian population were collected during 2004–2005 years. Samples were analyzed for contamination with aflatoxins, ochratoxin A and zearalenone, using competitive enzyme-linked immunosorbent assay (ELISA). The predominant mycotoxin was ochratoxin A with a mean level of 3.5 ± 5.3 ng g⁻¹ in 59.8% of studied samples. Furthermore, Aflatoxins were detected in all analyzed commodities with a contamination frequency of 50.5%. In addition, aflatoxin B1 was found in 37% of the samples. The zearalenone was detected around 15% with a mean level of 10.4 ± 11.8 ng g⁻¹. Species, dried fruits and sorghum were the most contaminated samples by aflatoxin and ochratoxin mycotoxins, whereas Rice was the least contaminated commodity. The most frequent mycotoxins co-occurrence included aflatoxins and ochratoxin A, which have been detected in 33.8% of analyzed samples. Furthermore, the simultaneous contamination by aflatoxins, ochratoxin A and zearalenone was observed in 7.2% of studied samples.     

Determination of Fusarium mycotoxins enniatins,beauvericin and fusaproliferin in cereals and derived products from Tunisia

In this study, 51 samples of cereals (wheat, Barley, maize and Sorghum) and by-products (mainly pasta and couscous) purchased from Tunisian supermarkets were examined for contamination with the emerging Fusarium mycotoxins: Enniatins ENs (EN A, EN A₁, EN B and EN B₁), beauvericin (BEA) and fusaproliferin (FUS).The extraction of the samples was performed with methanol using an Ultra-turrax homogenizer. Mycotoxins were analyzed with a liquid chromatography (LC) coupled to a diode array detector (DAD).The frequencies of contamination of total samples with ENs were 96%. EN A₁ was the most common EN found with the highest prevalence of 92.1%, levels ranged between 11.1 and 480 mg/kg. EN B was evidenced in 35 samples and levels ranged from 1.5 to 295 mg/kg. EN B₁ was detected in 20 samples (39.2%) and levels varied from 4.8 to 120.1 mg/kg and EN A was detected in 14 samples with contamination levels ranging between 19.6 and 121.3 mg/kg. The maximum concentration of total ENs in a single sample was 683.9 mg/kg (sorghum). The analytical results also showed that all the analyzed samples were free of BEA and FUS.The present work is the first one ever drafted on the presence of the emerging Fusarium mycotoxins in Tunisian cereals and derived products.     

Kinetics of Ochratoxin A Production and Accumulation by Aspergillus carbonarius on Synthetic Grape Medium at Different Temperature Levels

ABSTRACT:  The effects of incubation time (up to 10 d) and temperature (7, 15, 20, 25, 30, 35, and 42 °C) on mean ochratoxin A (OTA)-producing capacity and OTA accumulation by 4 Aspergillus carbonarius strains isolated from Spanish and Tunisian grapes were studied on grape-like medium. The limits of growth and OTA production have been identified. OTA production was significantly higher at 20 °C, followed by 25, 15, 30, 35 °C. No growth was observed at 7 °C and 42 °C after 10 d of incubation and, consequently, no OTA was detected at these temperature levels. In general, maximum mean OTA-producing capacity was found earlier with increasing incubation temperatures. However, at 35 °C, OTA was rarely detected although growth was maximum at this temperature. OTA accumulation was maximum after 10 d of incubation for all the temperatures except at 30 °C, were the maximum was detected at earlier incubation time (6 to 8 d) and then remained stable. Colony diameters and OTA accumulation along time were modeled by the Gompertz sigmoidal model and an estimation of maximum OTA accumulation rate and the delay until OTA production could be established. At high temperatures OTA accumulation starts earlier but increases slowly and becomes constant in a few days.