Analytical applications of 2,6-diacetylpyridine bis-4-phenyl-3-thiosemicarbazone and determination of Cu(II) in food samples

New synthesized reagent 2,6-diacetylpyridine bis-4-phenyl-3-thiosemicarbazone (2,6-DAPBPTSC) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of copper(II) at pH 3.0 to form a yellowish orange colored 1:1 chelate complex. The maximum absorbance was measured at 370 nm. This method obeys Beer’s law in the concentration range 0.63–6.30 g ml⁻¹ and the correlation coefficient of Cu(II)–2,6-DAPBPTSC complex is 0.942, which indicates an adequate linearity between the two variables with good molar absorptivity and Sandell’s sensitivity, 0.847 × 10⁴ l mol⁻¹ cm⁻¹ and 0.0075 g cm⁻², respectively. The instability constant of complex calculated from Asmus′ method is 1.415 × 10⁻⁴ at room temperature. The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.777% and the detection limit value is 0.0056 g ml⁻¹. The interfering effect of various cations and anions has also been studied. The method was successfully applied for the determination of Cu(II) in food samples. The performance of present method was evaluated in terms of Student ‘t’ test and Variance ‘f’ test, which is indicates the significance of present method is an inter comparison of the experimental values, using atomic absorption spectrometer (AAS).     

N-(carboxymethyl)lysine content of foods commonly consumed in a Western style diet

The potential adverse effects on health of diet-derived advanced glycation end-products (AGEs) is of current interest, due to their proposed involvement in the disease progression of diabetic and uraemic conditions. However, accurate information about levels of AGEs in foods is lacking. The objective of this investigation was to determine the level of one particular AGE, N^ε-(carboxymethyl)lysine (CML), a marker of AGE formation, in a wide range of foods commonly consumed in a Western style diet. Individual foods (n = 257) were mixed, lyophilised, ground, reduced, fat-extracted, hydrolysed, and underwent solid-phase extraction. Extracts were analysed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Cereal (2.6 mg/100 g food) and fruit and vegetable (0.13 mg/100 g food) categories had the highest and lowest mean level of CML, respectively, when expressed in mg/100 g food. These data can be used for estimating potential consumer intakes, and provide information that can be used to educated consumers on how to reduce their CML intake.     

Zn(Ⅱ)-PYPAPT-Triton X-100光度法测定食品中微量锌

研究了1-吡啶-3-[4-(苯基偶氮)苯基]-三氮烯(PYPAPT)与锌离子(Zn2 )的光度法测定微量锌。在非离子表面活性剂TritonX-100存在下和NaOH介质中,Zn2 与PYPAPT形成1∶2红色配合物。配合物最大吸收波长位于520nm,表观摩尔吸光系数ε520为1.54×105L·mol-1·cm-1,Zn2 含量在0～0.32mg/L范围内符合比尔定律。研究测定微量锌的新光度法灵敏度高,操作简便,应用于食品中微量锌的测定,结果满意。测定结果与国标(GB)双硫腙方法测定的结果吻合。     

A Sensitive, Selective New Analytical Reagent, 2, 6-Diacetylpyridine bis-4-phenyl-3-thiosemicarbazone for Extractive Spectrophotometric Determination of Mo(VI) in Food Samples

Synthesized a new reagent 2, 6-Diacetylpyridine bis-4-phenyl-3-thiosemicarbazone (2, 6-DAPBPTSC) characterized and is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of molybdenum(VI) at pH 3.5 to form a yellowish orange colored 1:1 chelate complex. The absorbance was measured at a maximum wavelength, 500 nm. This method obeys Beer’s law in the concentration range 0.90–9.00 μg mL⁻¹ and the correlation coefficient of Mo(VI)–2,6-DAPBPTSC complex is 0.954, which indicates an adequate linearity between the two variables with good molar absorptivity and Sandell’s sensitivity, 1.212 × 10⁴ L mol⁻¹cm⁻¹, 0.0079 μg cm⁻², respectively. The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.894% and the detection limit value is 0.0056 μg mL⁻¹. The instability constant of the method has been calculated by Asmus’ method as 6.476 × 10^–5, at room temperature. The interfering effect of various cations and anions has also been studied. The method was successfully applied for the determination of Mo(VI) in food and water samples. The validity of the present method was evaluated in terms of Student ‘t’ test and Variance ‘f’ test, which indicates the significance of the present method an inter comparison of the experimental values, using atomic absorption spectrometer.     

Role of proline and hydroxyproline in N-nitrosamine formation during heating in cured meat

N-Nitrosamines are formed in a multi-step reaction of nitrite with free amino acids and amines in the meat products. The aim of this study was to determine the role of proline and hydroxyproline in N-nitrosamines formation during heating of cured meat. A lean meat model was used with different nitrite concentrations (0, 120, and 480 mg/kg), and addition of proline and hydroxyproline (1000 mg/kg), followed by heating at different temperatures. Volatile nitrosamines were analyzed with GC-TEA.     

Influence of putrescine,cadaverine, spermidine or spermine on the formation of N-nitrosamine in heated cured pork meat

The influence of biogenic amines (i.e. putrescine, cadaverine, spermidine and spermine) on the N-nitrosamine formation in heated cured lean meat was studied in the presence or absence of sodium nitrite and at different meat processing temperatures. Experimental evidence was produced using gas chromatography with thermal energy analysis detection (GC–TEA). Concentration of N-nitrosamines was modelled as a function of the temperature and the nitrite concentration for two situations, i.e. presence or absence of added biogenic amines to the meat. The significance of the influence of the changing parameters was evaluated by ANOVA (Analysis of Variance).     

Spectrophotometric determination of total serotonin derivatives in the safflower seeds with Ehrlich’s reagent and the underlying color reaction mechanism

A new spectrophotometric method for the determination of total serotonin derivatives in the safflower (Carthamus tinctorius L.) seeds is described. The determination is based upon a color reaction between serotonin derivatives and p-dimethylaminobenzaldehyde (Ehrlich’s reagent), which follows the electrophilic substitution reaction mechanism at the indole ring. The main factors affecting correct measurement of total serotonin derivatives concentration were studied. The maximum absorption wavelength of the complex was determined at 625 nm. Lambert-Beer’s law is obeyed in the concentration range of 0.025–0.5 mmol/l, with a correlation coefficient (R²) of 0.9996, a recovery of 99.7%, and a relative standard derivation (RSD) of 1.5%, respectively. The proposed method presented satisfactory results in the determination of total serotonin derivatives in the extract from a strain of safflower seeds, and thus is recommended as a routine method for total serotonin derivatives quantitation.     

Benzyloxybenzaldehydethiosemicarbazone: Extractive Spectrophotometric Reagent for the Determination of Cu(II) in Food and Water Samples

Benzyloxybenzaldehydethiosemicarbazone (BBTSC) was prepared and developed a new method for the simple, highly selective, and extractive spectrophotometric determination of copper(II) with BBTSC at wavelength 370 nm. The metal ion formed a bluish green colored complex with BBTSC in acetate buffer of pH 5.0, which was easily extractable into n-butanol with 1:1(metal/ligand) composition. The method obeys Beer’s law in the range of 0.5–5.2 ppm. The molar absorptivity and Sandell’s sensitivity were found to be 1.5 × 10⁴ l mol⁻¹ cm⁻¹ and 0.00412 g cm⁻², respectively. The correlation coefficient of the Cu(II)–BBTSC complex was 0.998, which indicated an excellent linearity between the two variables. The repeatability of the method was checked by finding the relative standard deviation (RSD; n = 10), which was 0.377% and its detection limit 0.0204 μg ml⁻¹. The interfering effect of various cations and anions were also studied. The proposed method was successfully applied to the determination of copper(II) in food and water samples. Comparing the results with those obtained using an atomic absorption spectrophotometer tested the validity of the method.     

Short communication: Establishment of a new polymerase chain reaction-sequence-based typing method for genotyping cattle major histocompatibility complex class II DRB3

Sequence-based typing (SBT) is the most comprehensive method for characterizing major histocompatibility complex (MHC) gene polymorphisms. We report here a new PCR-SBT method for genotyping cattle MHC (BoLA) class II DRB3 using the Assign 400ATF ver. 1.0.2.41 software (Conexio Genomics, Fremantle, Australia), which detects alleles in a semiautomated manner. We examined 12 sets of PCR reactions for their ability to amplify BoLA-DRB3 exon 2 and selected an optimal primer set, which used ERB3N-HL031 for first-round PCR and ALL-DRB3B for second-round PCR. Next, we constructed a BoLA-DRB3 allele database using the reference sequences of the Assign 400ATF software and successfully assigned heterozygous samples (including those with deletion alleles) using bidirectional sequencing, unlike our previously described method, which used unidirectional sequencing for detecting of deletion alleles. Next, blood samples of 128 Holstein cattle were used to correlate the results of our modified PCR-SBT method with those of our previously described PCR-SBT method. Each new PCR-SBT result corresponded completely with the DRB3 allele that was genotyped by our previously described PCR-SBT method. Moreover, we confirmed the accuracy of our modified PCR-SBT method by genotyping 7 sire cattle and their 22 calves using Japanese Black cattle. This new method will contribute to high-throughput genotyping of BoLA-DRB3 by sequence-based typing.     

Flow injection spectrophotometry using natural reagent from Morinda citrifolia root for determination of aluminium in tea

A flow injection (FI) spectrophotometric method with using natural reagent extracted from Morinda citrifolia root has been developed for determination of aluminium. The extract contained anthraquinone compounds which could react with Al³⁺ to form reddish complexes which had maximum absorption wavelength at 499.0 nm. The extract could be used as a reagent in FI system without further purification to obtain pure compound. A sensitive method for determination of aluminium in concentration range of 0.1-1.0 mg L⁻¹, with detection limit of 0.05 mg L⁻¹ was achieved. Relative standard deviations of 1.2% and 1.7% were obtained for the determination of 0.1 and 0.6 mg L⁻¹ Al³⁺ (n = 11). Sample throughput of 35 h⁻¹ was achieved with the consumption of 3 mL each of carrier and reagent solutions per injection. The developed method was successfully applied to tea samples, validated by the FAAS standard method. The method is simple, fast, economical and could be classified as a greener analytical method.     

Spectrophotometric study of the copigmentation of malvidin 3-O-glucoside with p-coumaric,vanillic and syringic acids

Anthocyanins are a natural source of pigments in plants and their processed food products have become attractive and excellent candidates to replace the synthetic colourants due to their characteristic intense colours and associated health benefits. The intermolecular copigmentation between anthocyanins and other colourless compounds has been reported to be an important way to enhance and stabilise the colour intensity of aqueous solutions. In the present work we report the equilibrium constant, stoichiometric ratio and the thermodynamic parameters (ΔG°, ΔH° and ΔS°) related to the intermolecular copigmentation reactions of the anthocyanin malvidin 3-O-glucoside with one hydroxycinnamic acid (p-coumaric acid) and two O-methylated hydroxybenzoic acids (vanillic and syringic acid). Different factors which affect their interactions such as copigment concentration, pH and temperature of the medium are examined at two pH levels (pH = 2.50 and 3.65) corresponding to those of the major food mediums where these reactions take place (fruit juices, wine, jams etc.).     

Identification of antioxidants in Fructus aurantii and its quality evaluation using a new on-line combination of analytical techniques

A new on-line method for simultaneous identification and monitoring of antioxidants in Fructus aurantii was established by coupling high performance liquid chromatography-diode array detector-electrospray ionisation-ion trap-time of flight-mass spectrometry with post-column derivatisation and luminol–potassium ferricyanide chemiluminescence (HPLC-DAD-ESI-IT-TOF-MS-PCD-LPFCL). While the HPLC fingerprint, structural identification and radical scavenging profile were rapidly obtained by an on-line assay using ultraviolet (UV) absorption, MS and LPFCL, details of the precise substitution patterns of various structures were achieved through UV absorption using PCD addition of shift reagents. Twenty-five flavonoids were identified by either their PCD and MS data or comparison with reference substances. Data collected both from chromatograms and activity profiles of 12 samples revealed significant differences among samples from different habitats. The results showed that this method was rapid and precise, and therefore would be an effective and sensitive method for biocompounds analysis and quality evaluation for complex food and medicinal samples.     

Trans fatty acids in a range of UK processed foods

A survey to determine the trans fatty acid content of a range of processed foods was carried out in response to recent reformulation work by the food industry to lower the artificial trans fatty acid content of processed products. Sixty two composite samples, made up of between 5 and 12 sub-samples, were collected in 2010 and were analysed for fatty acids, and a range of nutrients. The foods analysed included pizza, garlic bread, breakfast cereals, quiche, fat spreads, a range of fish and meat products, chips, savoury snacks, confectionery and ice cream. Levels of trans fatty acids were reduced considerably compared with previous UK analyses of similar foods where comparisons are possible. Concentrations of trans elaidic acid (t9-C18:1) from hydrogenated oils in all samples were <0.2 g/100 g food. These results confirm information provided by the food industry in 2007 on the levels of trans fats in key processed food sectors.     

食品反式脂肪酸检测方法研究进展

反式脂肪酸是一种具有反式构型不饱和脂肪酸,来源较为广泛;最近流行病学调查研究表明,反式脂肪酸对人体健康有很大危害,因此,世界粮农组织和世界卫生组织提出食品中反式脂肪酸含量应低于4%,欧洲各国也限定食品中反式脂肪酸含量。该文介绍近年国外反式脂肪酸检测方法研究进展,为我国反式脂肪酸检测提供参考。     

Predicting relative concentrations of bioavailable iron in foods using in vitro digestion: New developments

In vitro methods have been developed for the prediction of iron bioavailability from foods and supplements. The dialyzability method measures dialyzable iron, released during a simulated gastrointestinal digestion, as an index of iron bioavailability. A new setup, that involves six-well plates and a ring insert that holds the dialysis membrane, is proposed for the application of the dialyzability method with the objective to increase efficiency and to allow testing small-volume samples. A series of solutions (water, ascorbic acid, and phytate), liquid foods (fresh milk and condensed milk), and solid foods (bread + meat meal, corn flakes), were tested in the presence or absence of added iron and digested with the new setup and the setup previously described for the dialyzability method. In both cases, percent dialyzable iron in each treatment remained similar (P > 0.05). These results suggest that the new setup can be employed in future applications with similar food matrices of the dialyzability method.     

Quantification of hesperidin in citrus-based foods using a fungal diglycosidase

A simple enzymatic–spectrophotometric method for hesperidin quantification was developed by means of a specific fungal enzyme. The method utilises the diglycosidase α-rhamnosyl-β-glucosidase (EC 3.2.1.168) to quantitatively hydrolyse hesperidin to hesperetin, and the last is measured by its intrinsic absorbance in the UV range at 323 nm. The application of this method to quantify hesperidin in orange (Citrus sinensis) juices was shown to be reliable in comparison with the standard method for flavonoid quantification (high performance liquid chromatography, HPLC). The enzymatic method was found to have a limit of quantification of 1.8 μM (1.1 mg/L) hesperidin, similar to the limit usually achieved by HPLC. Moreover, it was feasible to be applied to raw juice, without sample extraction. This feature eliminated the sample pre-treatment, which is mandatory for HPLC, with the consequent reduction of the time required for the quantification.     

Peach fruit acquired tolerance to low temperature stress by accumulation of linolenic acid and N-acylphosphatidylethanolamine in plasma membrane

Peach fruit (Prunuspersica L. cv. Beijing 33) did not show symptoms of chilling injury in 0 °C-Air or 0 °C-CA, but did in 5 °C-Air after 21 d. The mechanisms by which 0 °C storage could activate chilling tolerance of peach fruit were investigated by analysing characteristics of plasma membrane. We found that peach fruit stored in 0 °C-Air and 0 °C-CA had much higher linolenic acid content and unsaturation degree of plasma membrane than did that in 5 °C-Air. In addition, the fruits stored in 0 °C-CA showed a higher membrane fluidity and membrane integrity than did that in 0 °C-Air, which was related to the accumulation of N-acylphosphatidylethanolamine (NAPE) of peach fruits stored in 0 °C-CA. Based on these results, it appears that a higher unsaturation degree of membrane lipid and NAPE accumulation are beneficial for maintaining membrane fluidity, leading to an enhanced tolerance of peach fruit to chilling stress.