Effect of processing and storage conditions on the generation of acrylamide in precooked breaded chicken products

The generation of acrylamide was determined during frying and cold storage of breaded chicken products. The role of the batter crust on acrylamide formation also was evaluated. The effect of storage under a modified atmosphere on the fate of acrylamide was investigated during a 23-day storage period under refrigeration. Acrylamide was analyzed by using normal phase high-performance liquid chromatography according to a previously developed methodology that allows for dual identity verification as acrylamide and acrylic acid and determination of concentrations as low as 10 microg liter(-1), which corresponds to 20 microg kg(-1) of solid sample. For the total 28 commercial precooked samples analyzed, initial acrylamide concentrations ranged between 0.91 and 0.97 mg kg(-1) and were attributed to the combined effect of batter and meat. In all cases, acrylamide concentrations increased during storage, attaining a maximum (1.36 to 1.80 mg kg(-1)) between day 15 and day 19. The maximum value was observed in samples packaged under air, and the minimum value was observed under a modified atmosphere mixture of 60% CO2-40% N2. In this group, the maximum acrylamide concentration was reached after 19 days of storage. These data indicate that there is a high concentration of acrylamide in precooked, battered protein foods and that the concentration changes considerably during storage, which may lead to almost twice the initial amounts when air is present within the package.

Acid-induced phase separation of anionic surfactants for the extraction of 1,4-dichlorobenzene from honey prior to liquid chromatography

The acid-induced liquid-liquid phase separation of anionic surfactants in aqueous solutions and its applicability to cloud point extraction methodology were applied as a tool for the extraction of 1,4-dichlorobenzene (p-DCB) from aqueous samples. p-DCB is extracted into the micelles of sodium dodecane sulfonate (SDSA) in a 4.2 M HCl solution. The micellar phase is separated from the bulk aqueous solution after centrifugation and collected from the surface of the suspension. The micellar extracts are injected into a high-performance liquid chromatographic apparatus and quantified at 225 nm with a reference wavelength of 280 nm. Following the proposed methodology, a preconcentration factor of ca. 160 is achieved (starting from 50 mL solutions) allowing for detection limits at the low microg/L level. Application to honey samples produced detection limits of 2.5 microg/kg with quantification limits of 7.5 microg/kg, while the recoveries of the method ranged from 85% at high concentrations to 95% at lower concentrations of p-DCB. The combined uncertainty of the entire analytical procedure was 4.5% at the concentration level of 30 microg/kg allowing for reliable and reproducible results for the determination of p-DCB at the concentration levels considered as thresholds for EU and U.S. legislation (10 microg/kg).

Correlation between microbial flora, sensory changes and biogenic amines formation in fresh chicken meat stored aerobically or under modified atmosphere packaging at 4 °C: possible role of biogenic amines as spoilage indicators

This study evaluated the formation of biogenic amines (BAs) in breast chicken meat during storage under aerobic and modified atmospheric packaging (MAP) conditions at 4 degrees C, the correlation of microbial and sensory changes in chicken meat with formation of BAs and the possible role of BAs as indicators of poultry meat spoilage. Poultry breast fillets were stored aerobically or under MAP (30%, CO(2), 70% N(2)) at 4 degrees C for up to 17 days. Quality evaluation was carried out using microbiological, chemical and sensory analyses. Total viable counts, Pseudomonads and Enterobacteriaceae, were in general higher for chicken samples packaged in air whereas lactic acid bacteria (LAB) and Enterobacteriaceae were among the dominant species for samples under MAP. Levels of putrescine and cadaverine increased linearly with storage time and were higher in aerobically stored chicken samples. Spermine and spermidine levels were also detected in both aerobically and MAP stored chicken meat. Levels of tyramine in both chicken samples stored aerobically and or under MAP were low (< 10 mg kg(-1)) whereas the formation of histamine was only observed after day 11 of storage when Enterobacteriaceae had reached a population of ca. 10(7) CFU g(-1). Based on sensory and microbiological analyses and also taking into account a biogenic amines index (BAI, sum of putrescine, cadaverine and tyramine), BAI values between 96 and 101 mg kg(-1) may be proposed as a quality index of MAP and aerobically-packaged fresh chicken meat. Spermine and spermidine decreased steadily throughout the entire storage period of chicken meat under aerobic and MAP packaging, and thus these two amines cannot be used as indicators of fresh chicken meat quality.

Determination of acrylamide and methacrylamide by normal phase high performance liquid chromatography and UV detection

A method using normal phase high performance liquid chromatography (NP-HPLC) with UV detection was developed for the analysis of acrylamide and methacrylamide. The method relies on the chromatographic separation of these analytes on a polar HPLC column designed for the separation of organic acids. Identification of acrylamide and methacrylamide is approached dually, that is directly in their protonated forms and as their hydrolysis products acrylic and methacrylic acid respectively, for confirmation. Detection and quantification is performed at 200 nm. The method is simple allowing for clear resolution of the target peaks from any interfering substances. Detection limits of 10 microg L(-1) were obtained for both analytes with the inter- and intra-day RSD for standard analysis lying below 1.0%. Use of acetonitrile in the elution solvent lowers detection limits and retention times, without impairing resolution of peaks. The method was applied for the determination of acrylamide and methacrylamide in spiked food samples without native acrylamide yielding recoveries between 95 and 103%. Finally, commercial samples of french and roasted fries, cookies, cocoa and coffee were analyzed to assess applicability of the method towards acrylamide, giving results similar with those reported in the literature.

On-Line Solid-Phase Extraction with Surfactant Accelerated On-Column Derivatization and Micellar Liquid Chromatographic Separation as a Tool for the Determination of Biogenic Amines in Various Food Substrates

A sensitive method was developed for the determination of biogenic amines at very low levels by combining solid phase extraction (SPE) and derivatization on-line with HPLC. The on-line derivatization and SPE were performed simultaneously on a commercially available ODS guard column, which was installed instead of the filling loop on the HPLC apparatus. Resolution of the peaks and quantification was further enhanced with micellar liquid chromatography and sensitization of the benzene ring absorption at 254 nm. Detection limits of the benzoyl derivatives of biogenic amines were in the vicinity of 0.1 microg L(-)(1), which is even lower than those obtained by fluorescence detection and is unparallel to any other UV approach. The correlation coefficients of determinations were 0.9850-0.9998. The method was applied to the determination of Biogenic amines, that is, putrescine, cadaverine, agmatine, tyramine, tryptamine, phenylethylamine, spermine, spermidine and histamine in fish, chicken, and wine samples. Recovery of the proposed method ranged from 94 to 106%.

Determination of biogenic amines as their benzoyl derivatives after cloud point extraction with micellar liquid chromatographic separation

The advantages of micellar cloud point extraction combined with a surfactant-assisted separation in a HPLC system are presented as a method for the effective separation and determination of nine biogenic amines in fish substrates. Benzoyl derivatives of the amines are extracted inside the micelles of a non-ionic surfactant, Triton X-114, and separated with gradient elution micellar liquid chromatography. Quantification was performed by measuring the UV absorbance of the benzene ring at 254 nm. Detection limits of the nine biogenic amines were in the vicinity of 0.01 mg l(-1) which are approximately 10 times lower than those of the conventional method (HPLC-UV) and 100 times lower than those of micellar electrokinetic capillary chromatography. The correlation coefficients of determinations were 0.9911-0.9996. The method was applied for the determination of putrescine, cadaverine, agmatine, tyramine, tryptamine, phenylethylamine, spermine, spermidine and histamine in trout samples. Recovery of the proposed method ranged from 95 to 103.5%.

A simple empirical model for activated sludge thickening in secondary clarifiers

A simple empirical model for the thickening function of the activated sludge secondary clarifiers is presented. The proposed approach relies on the integration of previous models and it is based on the phenomenon of dilution of the incoming activated sludge in the feeding well of the settling tanks. The method provides a satisfactory description of sludge stratification within the clarifier. The only requirements are limited to parameters which are readily incorporated into the routine analysis performed in an activated sludge plant, thereby eliminating the need for additional experimental or computational effort. The method was tested in a full-scale activated sludge plant and it was found that it describes fairly well the return sludge concentration, the diluted sludge blanket concentration, the sludge blanket solids concentration and the sludge blanket height of full-scale secondary clarifiers.

Spectrofluorometric determination of vanadium based on the formation of a ternary complex between vanadium, peroxides, and 2-alpha-pyridylthioquinaldinamide. Application to the determination of hydrogen peroxide and peroxy acids

A selective and sensitive method for the determination of the total amount of vanadium in nutritional and biological substrates is proposed. The method is based on the reaction of vanadium with 2-alpha-pyridylthioquinaldinamide (PTQA) in the presence of H2O2. The product of this reaction emits constant fluorescence, in a sulfuric acid environment, at 490 nm, with the exciting radiation set at 340 nm. Various parameters such as acidity, flow rate, solvents, and temperature were studied. The presence of a surface-active agent was also considered in order to increase sensitivity. At the optimal conditions, a calibration curve was constructed, revealing a linear range of 2-100 microg L(-1) and a detection limit as low as 0.5 microg L(-1) while the RSD ranged in the area of 0.1-1.8%, depending on vanadium concentration. The method was successfully applied to the analysis of a wide variety of food samples, which are known to contribute to the dietary required amount of vanadium and to relevant biological matrixes. Reversing the conditions of the above reaction, the effect of the peroxy group on the vanadium-PTQA system was examined. The formation of a vanadyl complex was revealed which was suitable for the determination of hydrogen peroxide and peroxy acids. Linear calibration curves in the range of 0.2-50 microM for H2O2 and 0.1-2 microM for a respective peroxy acid were obtained, yielding detection limits of 0.05 and 0.03 microM, respectively.

Nonaqueous catalytic fluorometric trace determination of vanadium based on the pyronine B-hydrogen peroxide reaction and flow injection after cloud point extraction

The catalytic effect of vanadium on the pyronine B-H2O2 system is examined. Enhancement of the catalytic reaction rate along with the efficiency and selectivity against vanadium is achieved in a formic acid environment in the presence of a nonionic surfactant (Triton X-114). Elimination of drastic interference caused by inorganic acids and aqueous matrix along with a 50-fold preconcentration of vanadium are facilitated through cloud point extraction of its neutral complex with 8-quinolinol in an acidic solution. Subsequent flow injection analysis (FIA) with fluorometric detection renders the proposed method ideal for selective and cost-effective determination of as little as 0.020 microng L(-1) vanadium in environmental, biological, and food substrates. The preconcentration step can be applied simultaneously to multiple samples, allowing for massive preparation prior to analysis, compensating, thus, for the time-consuming procedure.

An optimised single-reagent method for the speciation of chromium by flame atomic absorption spectrometry based on surfactant micelle-mediated methodology

The toxicity of chromium in the environment is dependent on the species in which it exists. This paper outlines a method for the analysis of the oxidation states of Cr employing a suitable chelating agent and the cloud point phenomenon for Cr(VI) and total Cr analysis. The method involves preconcentration of metal chelates followed by air-acetylene flame atomic absorption spectrometric analysis. The chelating agent chosen for this task is the ammonium pyrrolidinedithiocarbamate, which reacts with either Cr(VI) or total Cr under specific experimental conditions. The condensed surfactant phase with the metal chelate(s) is introduced into a flame atomic absorption spectrometer, whereby discrimination of Cr species is feasible by calculating the Cr(III) concentration from the difference between total Cr and Cr(VI). A multivariate design was employed to study the variables affecting the overall analytical performance for total Cr assay. The analytical curves are rectilinear up to 100 micrograms l-1 for both oxidation states of the metal. The limits of detection are 0.6 microgram l-1 and the relative standard deviation (n = 5) at a concentration of 30 micrograms l-1 for both species is around 2.0%. The method was validated by analysing BCR 544 reference material certified for both Cr species. High recoveries in the range 96-107% were attained for the environmental and biological samples tested.