Quantitative and confirmatory analyses of malachite green and leucomalachite green residues in fish and shrimp

Liquid chromatographic methods are presented for the quantitative and confirmatory determination of malachite green (MG) and leucomalachite green (LMG) for channel catfish, rainbow trout, tilapia, basa, Atlantic salmon, and tiger shrimp. Residues were extracted from tissues with ammonium acetate buffer and acetonitrile and isolated by partitioning into dichloromethane. LMG was quantitatively oxidized to the chromic MG with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Extracts were analyzed for total MG by liquid chromatography with both visible detection (LC-VIS) at 618 nm for routine screening and ion trap mass spectrometry (LC-MSn) with no discharge-atmospheric pressure chemical ionization for residue confirmation. The method was validated in each species fortified with LMG at 1, 2, 4, and 10 ng/g (ppb), and average recoveries ranged from 85.9 to 93.9%. Quantitative data were consistent for the two detection methods, with measured method detection limits of 1.0 ng/g for LC-VIS and 0.25 ng/g for LC-MSn. Incurred tissues from catfish, trout, tilapia, and salmon that had been treated with MG were also extracted and analyzed as part of this study.     

Determination of phosphate in solution at different ionic composition using malachite green

Abstract

The malachite green method was sometimes used to determine low concentrations of inorganic phosphate due to its high sensitivity. The aim of this work was to test the suitability of this method for the determination of phosphorus (P) extracted by various reagents, e.g., KCl 0.01–1.20M, CaCl₂ 0.01–0.1M, Na₂SO₄ 0.01–0.40M, NaHCO₃ 0.1M at pH 8.5, and NaOH 0.1M+NaCl 1M. The malachite green method was also compared with the traditional molybdenum blue method on 35 soil extracts. Color development reached stability within 2 hrs and was stable for up to 24 hrs for dilute solutions. For concentrated solutions the stability was inversely proportional to the concentration of the reagent. Salt concentration appeared to have no effect on absorbance in KCl extracts of up to 1.2M and in Na₂SO₄ extracts of up to 0.05M. Higher concentrations of sodium sulfate induced flocculation and precipitation of the dye complex, as did CaCl₂ above 0.04 M. A strong correlation was found between the malachite green and the molybdenum blue method. The malachite green method can be used for P determination in soil extracts when appropriate time of color development is provided and salt concentration is taken into account.     

Automated determination of trace amounts of phosphate in soil extracts using malachite green

Abstract

A sensitive and simple automatic continuous‐flow determination of orthophosphate at trace levels has been worked out. The detection limit was lower than 2 μg/L. The interferences due to silicate and dissolved organic matter in soil extracts have been eliminated.     

Determination of fluoride in deboned meat

A rapid analytical procedure was investigated for measuring the fluoride content of deboned meat, using a specific ion electrode. The method involves a defatting procedure followed by chelation with EDTA before final solubilization and measurement. Fluoride content is determined by comparison to a standard curve on 2-cycle semi-logarithmic graph paper of fluoride ion vs. millivolt readings. The method is applicable to hand and mechanically deboned pork, beef, and poultry within a range of from 0.7 to 25.0 ppm fluoride. Higher concentrations may be measured by analyzing additional standards and extending the curve into a third cycle. The curve is not linear below 0.7 ppm. Samples less than 0.7 ppm may be estimated by extrapolation. Studies with fortified samples indicate average recoveries of 92 +/- 4.2%. The standard deviation of duplicates within the laboratory is 0.5 ppm in the range stated above.     

Production of antibodies for selective detection of malachite green and the related triphenylmethane dyes in fish and fishpond water

This study provides a practical method for production of the antibodies against malachite green (MG) and its primary metabolite leucomalachite green (LMG). Two ELISA kits are constructed with the MG and LMG antibodies for detection of the residual MG and LMG in fish muscle and fishpond water. The detection limit is established at the level of 0.05 microg/L for both MG and LMG. Our ELISA kits show the advantages of good specificity, high sensitivity, and convenience in rapid screening of MG and LMG residues. The sample of fishpond water, without extraction or prior preparation, is directly assayed by the ELISA kit. More then 80 fish samples can be simultaneously tested in a kit. The toxic crystal violet and its metabolite leucocrystal violet of illegal use in aquaculture are detected by our prepared MG and LMG antibodies, whereas the antibodies do not cross-react with common antibiotics, sulfonamides, and benzene derivatives.     

Analysis of the early stages of lipid oxidation in freeze-stored pork back fat and mechanically recovered poultry meat

An analytical method that can detect low levels of oxidation in food earlier than a sensory panel would be a valuable tool for food manufacturers as well as research institutes. Two model matrixes, pork back fat and mechanically recovered poultry meat (MRPM), were freeze-stored in air at -20 degrees C for 26 weeks. Peroxide value, thiobarbituric acid reactive substances, volatiles analyzed with dynamic headspace gas chromatography-mass spectrometry (GC-MS) and a gas-sensor array technique (electronic nose), chemiluminescence, and front-face fluorescence were evaluated against sensory analysis with regard to detection of early oxidation and correlation with sensory data. Fluorescence and GC-MS could detect oxidative changes in pork back fat earlier than the sensory panel and the electronic nose at the same time. The three methods were highly correlated with sensory attributes (r = 0.8-0.9). GC-MS gave the best results with regard to detection of small oxidative changes in MRPM.     

Development of poultry rapid overnight field identification test (PROFIT)

A poultry rapid overnight field identification test (PROFIT) has been developed as a screening test which is practical, economical, and easy to perform and interpret for use in field environments to determine the presence of poultry tissue (chicken and turkey) in raw whole tissue or ground/formulated meat products. The basis of the test is an agar-gel immunodiffusion technique used with a printed template pattern and stabilized reagent paper discs. The test shows adequate sensitivity and specificity for its intended purpose. Key components are stable for at least 1 year if they are stored at refrigerator conditions. The design of the test is such that it can be made commercially available as a complete, stable, test kit suitable for use by any type of inspection program concerned with verification of poultry species in meat and/or poultry products that are subject to regulatory or quality controls.     

Reevaluation of Monier-Williams method for determining sulfite in food

The Monier-Williams distillation procedure has a long history of successful use for determining sulfite in fruit products and wine; however, a systematic evaluation of its accuracy and precision with other food matrices has not been undertaken. We found that the Monier-Williams distillation yielded greater than 90% recovery of sulfite added to foods such as table grapes, hominy, dried mangoes, and lemon juice. Less than 85% recovery was obtained with broccoli, soda crackers, cheese-peanut butter crackers, mushrooms, and potato chips. These results may, in fact, accurately reflect the residual levels of sulfite if a portion of the sulfite undergoes irreversible reaction with some food components. Analysis of commercial food products gave sulfite levels ranging from 1400 ppm in dried apple slices to 25 ppm in cream sherry.     

Determination of malachite green residues in fish using a highly sensitive electrochemiluminescence method combined with molecularly imprinted solid phase extraction

An electrochemiluminescence (ECL) inhibition method combined with molecularly imprinted solid phase extraction (MISPE) was developed for quantitative determination of malachite green (MG) residues in fish. It was found that MG could strongly inhibit the ECL signal of luminol. Under the optimized conditions, the quenched ECL intensity versus the logarithm of the concentration of MG was in good linear relationship over a concentration range from 20 to 5000 ppt. The method detection limit was found to be about 6 ppt. Molecularly imprinted polymers (MIPs) were synthesized as solid phase extraction (SPE) sorbents, and MISPE was used for the selective extraction and purification of MG. By carrying out the oxidation reaction with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), which could convert leucomalachite green (LMG) into MG, this method was successfully applied to determine MG residues in fish. A possible mechanism for the quenching effects of MG on luminol was also proposed.     

Detection of irradiated ingredients included in low quantity in non-irradiated food matrix. 1. Extraction and ESR analysis of bones from mechanically recovered poultry meat

Protocol EN 1786 for the detection of irradiated food by electron spin resonance (ESR) spectroscopy was not conceived for the detection of irradiated bone-containing ingredients included in low concentration in non-irradiated food. An enzymatic hydrolysis method, realized at 55 degrees C, has been developed for the extraction of the bone fraction. When followed by a purification of the extracts by an aqueous solution of sodium polytungstate, this method made possible the detection of irradiated mechanically recovered poultry meat at very low inclusions (0.5%, wt/wt by ESR) in various meals (quenelles and precooked meals).     

Detection of irradiated ingredients included in low quantity in non-irradiated food matrix. 2. ESR analysis of mechanically recovered poultry meat and TL analysis of spices

Protocols EN 1786 and EN 1788 for the detection of irradiated food by electron spin resonance spectroscopy (ESR) and thermoluminescence (TL) were not conceived for the detection of irradiated ingredients included in low concentration in nonirradiated food. An enzymatic hydrolysis method, realized at 55 degrees C, has been developed for the extraction of silicate minerals and bone fragments. When followed by a purification of the extracts by an aqueous solution of sodium polytungstate, this method made it possible to detect very low inclusions of irradiated spices (0.05%, wt/wt by TL) included in various meals (cheeses and precooked meals). Even for food containing together two ingredients (spices and mechanically recovered meat), it was possible to detect and identify them simultaneously.     

Detection of sialylated phosphorylated kappa-casein glycomacropeptide electrophoresed on polyacrylamide gels and cellulose acetate strips by the thiobarbituric acid and malachite green dye reactions

A 64 amino acid residue sialylated phosphorylated glycomacropeptide (GMP) from bovine sweet whey can be detected as a Coomassie blue-staining peptide by electrophoresis on sodium dodecyl sulfate (SDS)-polyacrylamide gels. There is, however, limited information available concerning detection of GMP as a sialylated phosphorylated compound. Samples of GMP were electrophoresed on SDS-polyacrylamide gels or cellulose acetate strips (CAS). Immediately following electrophoresis, fractions obtained by cutting gels or strips were subjected to sialic acid determination by the thiobarbituric acid reaction and phosphorus determination by the malachite green dye reaction. Both determinations were found to be sensitive enough to detect approximately 20 and 40 microg of GMP in CAS and SDS gels, respectively. Further studies demonstrated that sialylated phosphorylated GMP can be detected on either SDS gels or CAS loaded with whey products or whey-added margarine residues.     

A boron-dipyrromethene-based fluorescent probe for colorimetric and ratiometric detection of sulfite

BODIPY-Le, a colorimetric and ratiometric fluorescent probe based on boron-dipyrromethene for selective detection sulfite ion, was investigated. Boron-dipyrromethene levulinyl ester (BODIPY-Le) is composed of an indole-based BODIPY dye and the levulinyl protective group, which could be easily and selectively deprotected by sulfites. As a result, the absorption and emission spectra show a dramatic red shift, and the development of a colorimetric and ratiometric fluorescent sulfite probe could be achieved. Besides, BODIPY-Le also exhibited prominent turn-on or turn-off type fluorogenic signaling toward sulfite ions once excited at 510 and 620 nm, respectively.     

Determination of sulfite in food by flow injection analysis

A method is described for the determination of sulfite levels in food products by flow injection analysis (FIA). The method is based on the decolorization of malachite green by SO2, which is isolated from the flowing sample stream by means of a gas diffusion cell. The FIA method has a detection limit in food sample extracts of 0.1 ppm SO2 (3 times peak height of blank), which corresponds to 1-10 ppm SO2 in a food product, depending on the extraction procedure used. At the 5 ppm SO2 level in a food extract, the precision of replicate injections is +/- 1-2%. The method was tested on a variety of both sulfite-treated and untreated food products and the results compared favorably with those obtained by the Monier-Williams, colorimetric (pararosaniline), and enzymatic (sulfite oxidase) methods. The average differences from the FIA results were 19, 11, and 12%, respectively, for those samples (n = 12) above 50 ppm SO2. At lower levels the results were somewhat more erratic due to inaccuracies of the various methods at low concentrations.     

Determination of sulfite in foods by headspace liquid chromatography

Sulfite was determined in a variety of foods by liquid chromatography (LC) after the samples were mixed with a solution containing mannitol, FeSO4, and Na2HPO4, adjusted to pH 11, and left to stand for 15 min at room temperature. An aliquot of the mixture was placed in a headspace vial and mixed with 50% H3PO4. After 15 min, a portion of the headspace was removed with a syringe containing LC mobile phase without acetonitrile. The syringe was shaken and an aliquot of the solution was analyzed on an anion exchange column with a mobile phase of 0.03M methane sulfonate (pH 10.8) containing 5% acetonitrile. Sulfite was detected amperometrically (glassy carbon electrode) at +0.7 V. The method was successfully compared to the FDA-modified Monier-Williams procedure for a variety of foods. Minimum detectable levels were about 1 microgram/g, based on a 15 g sample.     

Lycopene production using Blakeslea trispora in the presence of 2-methyl imidazole: yield, selectivity, and safety aspects

The potential role of 2-methyl imidazole in improving lycopene production by Blakeslea trispora with regards to yield, selectivity, and safety aspects was investigated in batch culture. Optimization of the bioprocess conditions in terms of (a) (+) and (-) strain ratio in the inoculum, (b) initial crude soybean oil (CSO) addition level, and (c) the amount of 2-methyl imidazole was based on response surface methodology to achieve maximum lycopene production. The dependence of growth kinetics, lycopene yield, and selectivity of the bioprocess on the above factors was clear. 2-Methyl imidazole at 50 mg/L was found equally active in terms of lycopene cyclase inhibition with that at 200 or 100 mg/L; in all cases, lycopene accounted for 94% of the total carotenoids. The highest yield was observed at a 50 mg/L level of addition (24 mg/g of biomass dry weight,) in a substrate supplemented with CSO (48 g/L of culture medium) and inoculated with 1(+)/7(-) strain ratio.     

大型蛋鸡养殖场数字化应用平台设计

针对我国大型蛋鸡养殖场在生产管理信息化方面存在的不足，构建了大型蛋鸡养殖场的数字化平台。该平台包含了基于以太网的信息获取模块、基于音视频的远程交互式诊断系统和基于B／S架构的生产信息管理模块，通过对信息的整合，为生产管理与决策提供了更多的数据和技术支持。将该系统应用于大型养殖场，有利于提高管理效率和生产效益，为解决家禽规模化养殖在信息技术应用方面的瓶颈提供一个解决方案。     

大型蛋鸡养殖场数字化应用平台设计

针对我国大型蛋鸡养殖场在生产管理信息化方面存在的不足,构建了大型蛋鸡养殖场的数字化平台。该平台包含了基于以太网的信息获取模块、基于音视频的远程交互式诊断系统和基于B／S架构的生产信息管理模块,通过对信息的整合,为生产管理与决策提供了更多的数据和技术支持。将该系统应用于大型养殖场,有利于提高管理效率和生产效益,为解决家禽规模化养殖在信息技术应用方面的瓶颈提供一个解决方案。     

Analysis for total sulfite in foods by using rapid distillation followed by redox titration

A rapid and accurate analysis for total sulfite as sulfur dioxide has been developed for foods and food products. The method, which combines a selective distillation cleanup procedure with the selective redox titration of sulfite ion by iodine, has been applied to a variety of foods and food products over a period of time with no significant interference encountered in any matrixes other than garlic and leeks. For the foods analyzed, the method typically shows a detection limit of 10 ppm, a relative standard deviation of 7.5% (compared with 10.4% for similar matrixes by the Monier-Williams method), and recoveries of 97.9 +/- 6.4%. Comparison of results for this method with those obtained using the Monier-Williams method showed a mean value for the distillation/titration method of 241 ppm compared with 242 ppm for the Monier-Williams method. A correlation of 0.991 and odds of a difference between methods of 10.7% (Student's paired t-test (1-alpha) X 100) were obtained for those matrixes where no interferences were encountered with either method.