Determination and occurrence of 5-hydroxymethyl-2-furaldehyde in white and brown sugar by high performance liquid chromatography

5-hydroxymethyl-2-furaldehyde (HMF) is not only indicator of food freshness and quality, but also contaminant forming during Maillard reaction, or by dehydratation of saccharides, respectively. While data about presence of HMF in white and brown sugar are scarce, 13 kinds of white sugar and 25 kinds of brown sugar were analysed. Sugar was dissolved in deionised water, clarified with Carrez solutions, filtered and content of HMF was determined using high performance liquid chromatography with diode array detector (HPLC-DAD) with detection at 284 nm when separation run on Poroshel 120 EC C18 at 32 °C. Elution was performed under isocratic conditions using 95:5 water/acetonitrile mobile phase at a flow rate of 0.9 mL/min and analysis run 5 min. Method was validated in in house regime and its parameters such as limit of detection – (LOD = 0.05 mg/kg), limit of quantification (LOQ = 0.15 mg/kg), specificity, repeatability and recovery enabled its application for sugar analysis. While white sugar was free of HMF, all kinds of brown sugar exhibited presence of HMF, when content in 15 kinds varied between 0.17 and 6.45 mg/kg, content in other 10 kinds was under LOQ. On the base of obtained results was postulated that brown sugar contains HMF either due to absence of refining processes, or it is re-contaminated by treacle adding to white sugar during production of brown sugar.     

5-羟甲基糠醛加氢催化剂的性能研究

介绍了负载型5 羟甲基糠醛(HMF)加氢催化剂的制备方法，对所制备的催化剂进行了N₂吸附-脱附等温线、透射电镜、氢氧滴定、吡啶红外等表征，并采用高压反应釜装置对其催化加氢性能进行了评价。比较了Ru、Rh、Pd、Pt 4种贵金属，MoO₃、WO₃、ReO₃ 3种助剂，SiO₂、Al₂O₃、Y型分子筛、S-1分子筛、MCM-41介孔材料5种载体对HMF加氢反应催化剂性能的影响，结果表明，以SiO₂为载体负载Pt及助剂MoO₃制得的催化剂性能较好。HMF呋喃环侧链C—C键和C—O键的断裂是引发后续副反应的重要原因，抑制HMF呋喃环侧链C—C键和C—O 键的断裂是提高HMF加氢反应目标产物选择性的关键。     

Survey of undeclared allergenic pistachio (Pistacia vera) in commercial foods by hydrolysis probe real-time PCR

Tree nut allergies represent an important health problem in industrialized countries. Among these, pistachio (Pistacia vera) kernels which are consumed as snack foods and used as ingredients in confectionery, chocolates, meat products, and ice-cream industries have been reported to cause IgE-mediated allergic reactions. Trace amounts of undeclared pistachio allergens can cause serious health risks for food-allergic consumers. In order to provide an appropriate method for the detection of pistachio in food products, a real-time polymerase chain reaction (PCR) system for the specific and sensitive detection of pistachio was developed. The sensitivity was investigated on spiked wheat flour samples with defined raw and heat-treated pistachio contents (0.1–100,000 mg kg⁻¹). The real-time PCR detected pistachio in these mixtures down to the lowest investigated spike level of 0.1 mg kg⁻¹. In addition, analysis of different retail samples from the market was performed to demonstrate the suitability of the assay in the food industry. The real-time PCR results obtained from the analysis of 229 commercial food products revealed 29 that didn't declare pistachio or traces on the label but were found to contain pistachio. The presented real time PCR method is useful for relatively fast, highly selective, and sensitive detection of pistachio in food samples.     

Methods for the determination of HMF in honey: a comparison

HMF (5-hydroxymethylfurfuraldehyde) is essential to evaluate the conformity of honey to the current legislation. Elevated concentrations of HMF in honey provide an indication of overheating, storage in poor conditions or age of the honey. Both the Codex Alimentarius Commission (Alinorm 01/25, 2000) and the European Union (Directive 110/2001) established that its concentration in honey usually should not exceed 80 or 40 mg/kg, respectively. The International Honey Commission recommends three methods for the determination of HMF: two spectrophotometric methods, determination after White and after Winkler and a HPLC method. These methods were recently tested by the International Honey Commission (1999). Aim of this research was to compare HMF values in unifloral honeys measured by the three methods. From our data, HPLC and White methods usually give similar values, except for eucalyptus honey; Winkler method gave for all honeys higher values than other two methods.     

Development of a PCR protocol to detect patulin producing moulds in food products

Patulin is a secondary toxic metabolite with important health effects. Several mould species of Penicillium and Aspergillus genera associated with patulin production have been detected in food products. Thus, specific and sensitive methods to detect patulin producing moulds are needed. The aim of this work was to develop a polymerase chain reaction (PCR) method to detect patulin producing moulds in food. 34 patulin producing and 30 non-producing strains belonging to the main species usually reported in food products were used. Patulin production was firstly evaluated by mycellar electrokinetic capillary electrophoresis and high-pressure liquid chromatography-mass spectrometry in all tested strains. Biosynthesis was also used to develop PCR primers derived from the genes involved in patulin. By means of a primer pair based on the isoepoxydon dehydrogenase (idh) gene, a 496-bp amplicon was specifically detected in all the mould strains previously confirmed as patulin producing, regardless of their genus and species. With the developed method it was possible to detect down to 0.5 ng of pure DNA from producing strains and from 1.8 × 10² to 2.7 × 10³ conidia g^?1 in artificially inoculated foods. No relevant PCR inhibition due to food matrices was observed. The PCR protocol developed could be considered as an appropriate tool to detect patulin producing moulds in food products.     

Water content,water activity,water structure and the stability of foodstuffs

Determination of water content, whatever the accuracy of the analytical method, is not sufficiently informative in relation to the stability of the investigated food product. Water activity (a_w) brings a supplement of information as it accounts for the availability of water for degradation reactions.The understanding of why certain products are more stable than others at the same a_w needs an elucidation of water structure. Of particular importance are the interactions (hydrophilic, hydrophobic) between water and the components of the foodstuff and the effect of the soluble molecules of the food on the hydrogen bonding in solvent water.Studying water in foods should start with an anlytical determination of water content for commercial and legal reasons which are evident. This has to be completed with the measurement of the thermodynamic activity of water in the food. Such a parameter (a_w) should hold an important place in the identification of the food product, especially as regards its shelf life. A further step in unveiling the behaviour of water in foods consists in determining water molecules in the molecules in the studied food matrix.The tripartite (analytical, thermodynamical and structural) approach to water in foods will be examined based on examples of sugars and sugar rich products.     

Evaluation of dispersive liquid–liquid microextraction for the determination of patulin in apple juices using micellar electrokinetic capillary chromatography

Patulin (PAT) is a mycotoxin naturally found in fruits, including apples. Its occurrence as a natural contaminant of fruit juices is indicative of fruit quality in production. The European Union has set the maximum content of patulin in 50 μg kg⁻¹ for fruit juices and 10 μg kg⁻¹ for infant fruit juices. In this paper, dispersive liquid–liquid microextraction (DLLME) has been proposed for the extraction and preconcentration of PAT in apple juice, followed by its determination by micellar electrokinetic chromatography (MEKC) with diode-array detection. PAT has been analyzed in the presence of 5-hydroxymethylfurfural (HMF), which is the main interference in this kind of matrix. Variables affecting DLLME efficiency were optimized and the calibration curve was established for PAT in analyte standard solutions, applying the DLLME–MEKC procedure. The limit of detection was 0.6 μg L⁻¹ and recoveries obtained for spiked freshly-made apple juice samples at four different concentration levels (5, 20, 50 and 75 μg L⁻¹), were above 75% with RSD lower than 9%. This method can be classified as a green alternative, being successfully applied to the measurement of 19 apple juice samples obtained from different suppliers and supermarkets. The optimized DLLME–MEKC method is free from matrix effects and avoids the tedious matrix-matched or standard addition calibration method. Almost fifty percent of the samples were contaminated with a PAT content greater than the maximum content established by the European regulation.     

Monitoring the presence of residues of tetracyclines in baby food samples by HPLC-MS/MS

Tetracyclin is a group of antimicrobial permitted in animal food production, but their concentrations in food of animal origin should not exceed 100 μg kg⁻¹ (in meat and milk). Although the detection of these substances above these limits involves fines and jail for the producer, residues of tetracyclines are still being detected in food a potential risk to consumer health, especially babies.In the past, baby foods were carefully prepared at homes. However, modern lifestyles have led to the commercialization of ready-made baby food. Generally, these products are made with vegetable and meat from different animals, such as pork, chicken or beef. The presence of tetracyclines in meat at concentrations above 100 μg kg⁻¹ is forbidden in Europe by the Regulation 37/2010. Consequently this concentration is also applicable to the portion of meat present in baby food. Even if the presence of tetracyclines is controlled regularly in meat, they should also be monitored in baby food as babies are vulnerable to such as drugs.A rapid analytical method based on high-performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS) for quantification of four tetracyclines (tetracycline, chlortetracycline, doxycycline and oxytetracycline) in baby food is presented. The tetracyclines are extracted with EDTA-McIlvaine buffer, acidified at pH 4.0, followed by liquid–liquid extraction with ethyl acetate. The final extract is analysed within 19 min on a Sunfire HPLC column from Waters. Validation was performed according to the Commission Decision 2002/657/EC. The mean accuracy was 103 μg kg⁻¹, and the mean precision, was less than 23% for all the tetracyclines. The method was tested on 31 prepared baby food samples containing vegetable and beef. The presence of oxytetracycline was detected in one of the samples at a concentration of 5 μg kg⁻¹.     

A multiplex real-time PCR method for the quantitative determination of equine (horse) fractions in meat products

The recent horse meat scandal that rocked Europe in early 2013 shows how important it is for the routine food control authorities to constantly evolve analytical tools for the accurate evaluation of meat products among others, to ensure that product declaration and actual composition correlate. While in most cases qualitative detection approaches suffice for product evaluation, in other cases a quantitative analysis is important to distinguish between inadvertent contamination and deliberate adulteration.In this work an optimized real-time qPCR-based approach is presented and compared with another real-time based method for the detection of equine sequences among others in meat products. The method is a multiplex system for the simultaneous quantification of horse, beef, pork and sheep fractions, and was validated for use in the routine analysis of meat products. We describe a modular multiplex approach, where a quadruplex system (without sheep) and a pentaplex assay (with an integrated sheep detection system) can be applied in meat detection and quantification strategies. The analysis is matrix independent and relies on concomitant quantification of the animal species present in the food sample against the backdrop of myostatin, a universal sequence present in most mammalian and poultry species. The limit of detection of the analytical method was 10 genome copy equivalents. For validation of the method, meat samples comprising differing meat compositions were analysed, and the assay performed well in terms of robustness and reproducibility.     

Effectiveness of a phage cocktail as a biocontrol agent against L. monocytogenes biofilms

Listeria monocytogenes can persist and form biofilms in a food environment which are difficult to eradicate because biofilms are inherently resistant to a variety of antimicrobial treatments. Therefore, alternative approaches such as bacteriophages have been suggested as a promising biocontrol agent against biofilms. The aim of this study was to evaluate the efficacy of a cocktail bacteriophage product (ListShield™) against L. monocytogenes biofilms. These biofilms were established on lettuce, stainless steel, rubber, and a MBEC biofilm device and exposed to the ListShield™ phage preparation (1 × 10⁸ PFU/mL) for 2 h. ListShield™ had sufficient potency to significantly reduce the biofilm (P < 0.05) in all cases. Biofilm reduction achieved after ListShield™ treatment on the stainless steel coupon was 1.9–2.4 log CFU/cm² and on the rubber surface approximately 1.0 log CFU/cm². Phage application on lettuce inactivated biofilm bacteria up to 0.7 log CFU/cm². These results suggest that bacteriophage preparation ListShield™ is an effective tool for the inactivation of L. monocytogenes biofilms in the food industry.     

Development and application of an analytical procedure for specific migration of green tea compounds in IV gamma nectarine active packaging

The aim of study was to develop an easy and reliable method for the quantification of tea compounds migrated from an active packaging to the foodstuff, being IV gamma nectarine the product tested. The method was based on a solid phase extraction (SPE) followed by ultra performance liquid chromatography-mass spectrometry analysis. SPE conditions were first optimized by spiking the nectarine flesh 1% of tea extract in methanol. A previous dilution of the sample extract in water (1:10) was required to remove the major matrix interferences. Then, the washing was optimized for 10 mL water and the extraction was optimized for 0.8 mL methanol. SPE method provided recoveries ranging between 81 and 99%. Limits of detection (0.006–0.048 μg kg⁻¹), quantification (0.008–0.160 μg kg⁻¹) and reproducibility below to 4.2% were obtained. The method has been applied to IV gamma nectarine packaging containing green tea extract. Samples were analyzed by the methodology described and the specific migration values of tea compounds were for all the cases below to the limit of detection calculated ensuring food safety and quality of nectarine active packaging.     

六水合三氯化铬催化蔗糖脱水合成5-羟甲基糠醛

研究了用CrCl3·6H2O催化蔗糖脱水转化为5-羟甲基糠醛（HMF）的反应,考察了蔗糖浓度、催化剂用量、反应温度和反应时间对产率的影响。利用紫外分光光度法测定产物并计算产率。较佳反应条件为：蔗糖浓度0．3mol／L、催化剂用量（以蔗糖质量计）3％、反应温度160℃、反应时间30min,在此条件下,产物收率可达55．3％。     

Isolation of recombinant antibody fragments (scFv) by phage display technology for detection of almond allergens in food products

Tree nut allergies are considered an important health issue in developed countries. To comply with the regulations on food labeling, reliable allergen detection methods are required. In this work we isolated almond-specific recombinant antibody fragments (scFv) from a commercial phage display library bypassing the use of live animals, hence being consistent with the latest policies on animal welfare. To this end an iterative selection procedure employing the Tomlinson I phage display library and a crude almond protein extract was carried out. Two different almond-specific scFv (named PD1F6 and PD2C9) were isolated after two rounds of biopanning, and an indirect phage ELISA was implemented to detect the presence of almond protein in foodstuffs. The isolated scFvs demonstrated to be highly specific and allowed detection of 40 ng mL⁻¹ and 100 ng mL⁻¹ of raw and roasted almond protein, respectively. The practical detection limit of the assay in almond spiked food products was 0.1 mg g⁻¹ (110–120 ppm). The developed indirect phage ELISA was validated by analysis of 92 commercial food products, showing good correlation with the results obtained by a previously developed real-time PCR method for the detection of almond in foodstuffs. The selected phage clones can be affinity maturated to improve their sensitivity and genetically engineered to be employed in different assay formats.     

Subsurface inspection of food safety and quality using line-scan spatially offset Raman spectroscopy technique

Subsurface inspection of food and agricultural products is challenging for optical-based sensing techniques due to complex interactions between light and heterogeneous or layered samples. In this study, a method for subsurface food inspection was presented based on a newly developed line-scan spatially offset Raman spectroscopy (SORS) technique. A 785 nm point laser was used as a Raman excitation source. The line-shape SORS data from the sample was collected in a wavenumber range of 0–2815 cm⁻¹ using a detection module consisting of an imaging spectrograph and a CCD camera. Two layered samples, one by placing a 1 mm thick plastic sheet cut from original container on top of cane sugar and the other by placing a 5 mm thick carrot slice on top of melamine powder, were created to test the subsurface food inspection method. For each sample, a whole set of SORS data was acquired using one CCD exposure in an offset range of 0–36 mm (two sides of the incident laser point) with a spatial interval of 0.07 mm. Raman spectra from the cane sugar under the plastic sheet and the melamine powder under the carrot slice were successfully resolved using self-modeling mixture analysis (SMA) algorithms, demonstrating the potential of the technique for authenticating foods and ingredients through packaging and evaluating internal food safety and quality attributes. The line-scan SORS measurement technique provides a rapid and nondestructive method for subsurface inspection of food safety and quality.     

Temperature management for the quality assurance of a perishable food supply chain

Compared to most product supply chains, food supply chains are often more complex and more difficult to manage because the food product is perishable and has a short shelf life. A cold chain or temperature-controlled supply chain provides the essential facilities and methods required to maintain the quality and quantity of foods. Since foods can be time and temperature sensitive in nature, they need to be properly taken care of in terms of harvesting, preparation, packaging, transportation and handling – in other words, throughout the entire chain. Temperature is the most important factor in prolonging or maintaining the shelf life of perishables. Refrigeration is one of most widely used methods to date to slow the bacteria growth that leads to food deterioration. The proper control and management of temperature is crucial in delivering perishables to consumers and ensuring that those perishables are in good condition and safe to eat. This paper addresses the methods used to improve the ability to define an optimal target temperature for multi-commodity refrigerated storage. Simulation results support the fact that the presented methods provide more accurate results compared to the conventional method. In addition, an experiment with a Wireless Sensor Network (WSN) was conducted. As a result, the sensor-based methods for real time quality monitoring and assessment that consider product metabolism and Euclidean distance cost depending on temperature changes are found to be superior to the traditional visual assessment method.     

Ultrasonic extraction and determination of cyanuric acid in pet food

Cyanuric acid is attracting more attention due to its potential toxicity. In the present work, an ultrasonic extraction method in combining with high-performance liquid chromatography (HPLC) was proposed for the determination of cyanuric acid in pet food. Among different solvents, methanol was found to be the best one as the extractant due to the strong polarity of cyanuric acid and the interferences in the pet food. The ultrasonic energy permitted an extraction time as less as 30 min, which was much shorter than 240 min required in the magnetic-stirring extraction. Under the selected HPLC conditions, the HPLC method could respond linearly with cyanuric acid at concentrations from 0.008 to 4.0 mg mL^?1 with a detection limit of 0.002 mg mL^?1. In the analysis of practical spiked pet food samples, the new method yielded satisfactory results.     

5-羟甲基糠醛的制备及其催化氧化研究进展

综述了生物质基平台化合物5-羟甲基糠醛(HMF)的制备及其催化氧化研究进展。分析了果糖、葡萄糖、纤维素等碳水化合物制备HMF面临的挑战和解决方法。讨论了HMF氧化产品2,5-二甲酰基呋喃、2,5-呋喃二甲酸的催化合成及其应用。指出纤维素是碳水化合物脱水制备HMF的最终目标底物,并对纤维素制备HMF的研究及其催化氧化发展前景进行了分析。     

Comparison of bacterial inactivation with novel agitating retort and static retort after mild heat treatments

Lower thermal load on foods is desirable for food producers and consumers as the food gets higher quality. With reduced thermal load, the investigation of food safety is of importance. In this study, microbial inactivation efficacy of a new retort process with high frequency longitudinal agitation was compared to static retort process which was used as a benchmark. As a model, fish soup samples, inoculated with approximately 10⁸ cells/ml Listeria innocua, was exposed to mild heat treatments at 62, 65 and 68 °C. Results clearly demonstrated that agitating mode can provide equivalent lethality to the model organism L. innocua within significantly shorter heating times compared to static mode. Bacteria were not detected on TSA-YE plates after 11.5, 6.8 and 5.5 min processing in agitating mode; 77, 67 and 52 min processing in static mode at 62, 65 and 68 °C respectively. Bacterial inactivation in agitating mode was generally correlated with estimated inactivation based on product core temperature, D- and z-values for L. innocua. This may indicate that distribution of the heat load over the soup was enhanced through agitation. Results showed that utilization of high frequency longitudinal agitation mechanism in retorts is promising for reducing the thermal load on food products without compromising on food safety related to non-spore forming pathogens.     

C2SLDS: A WSN-based perishable food shelf-life prediction and LSFO strategy decision support system in cold chain logistics

Temperature monitoring, shelf-life visibility and Least Shelf-life First Out (LSFO) stock strategy are important contents in perishable food cold chain logistics for both cold chain managers and workers in order to reduce quality and economic losses. This paper illustrates a wireless sensor network (WSN) based integrated Cold Chain Shelf Life Decision Support System (C²SLDS) designed for perishable food product cold chain management. The system is implemented based on the WSN and time temperature indicator (TTI) features. Compared with traditional cold chain management methods used before, the C²SLDS not only bridges the information gap which exists between different cold chain phase enterprises and provide a seamless information flow along the whole chain but also enables cold chain enterprises to predict perishable food's shelf-life and helps make a smart LSFO strategy to reduce the quality and economic loss. System test and evaluation shows that the infield radio transmission is reliable and the whole system meets most of the users' requirements raised in system analysis.     

Detection of egg and milk residues on working surfaces by ELISA and lateral flow immunoassay tests

In the last few years awareness for allergen management has increased among operators in the food chain. Since a small quantity of allergenic food can trigger an allergic reaction, accurate information in food product labels is essential for people who suffer from food allergy. A key point to reduce the risk of uncontrolled allergen contamination is to implement a strict and validated cleaning process. In this work a sampling method based on swabbing has been optimized with two analytical methods (ELISA and lateral flow tests) for milk and egg analysis on surfaces. Swab material, extraction buffer composition, temperature, time for recovery and the quantity of the allergen residue on the surfaces have been evaluated and a specific procedure was proposed. The new method has demonstrated a good performance to recover egg or milk proteins from two typical working surfaces (stainless steel or Formica). Egg and milk powder were detected by ELISA at a level as low as 0.04 and 0.2 μg, respectively. However, the detection level with lateral flow tests rose to 0.07 μg for egg powder and 0.6 μg for milk, depending on the kind of surface. On average, repeatability of swabbing method ranged from 18 to 32%. Both methods could be applied for validation the cleaning processes and for a routine verification after cleaning.