Performance evaluation of a fluorescamine-HPLC method for determination of histamine in fish and fish products

A method for the quantification of histamine in fish and fish products using tandem solid-phase extraction and fluorescence derivatization with fluorescamine was previously developed. In this study, we improved this analytical method to develop an official test method for quantification of histamine in fish and fish products, and performed a single laboratory study to validate it. Recovery tests of histamine from fillet (Thunnus obesus), and two fish products (fish sauce and salted and dried whole big-eye sardine) that were spiked at the level of 25 and 50 μg/g for T. obesus, and 50 and 100 μg/g for the two fish products, were carried out. The recoveries of histamine from the three samples tested were 88.8-99.6% with good repeatability (1.3-2.1%) and reproducibility (2.1-4.7%). Therefore, this method is acceptable for the quantification of histamine in fish and fish products. Moreover, surveillance of histamine content in food on the market was conducted using this method, and high levels of histamine were detected in some fish products.     

Determination of histamine in fish and fish products by tandem solid-phase extraction

A simple and practical method was developed for the determination of histamine in fish and fish products by solid-phase extraction and fluorescence derivatization. Histamine was extracted with trichloroacetic acid. The extract was neutralized and diluted with phosphate buffer (pH 6.8), and cleaned up with a tandem-connected octadecyl silica (ODS) and strong cation exchange silica (SCX) cartridge. After removal of the solvent, histamine was derivatized with fluorescamine and analyzed by ion-paired reversed-phase high-performance liquid chromatography with fluorescence detection. Recovery tests of histamine from six kinds of fish and fish products showed acceptable recovery (83-92%) with low relative standard deviation (less than 5%). This method could be useful for determination of histamine in fish.     

Efficiency of risk-based vs . random sampling for the monitoring of tetracycline residues in slaughtered calves in Switzerland

In all European Union countries, chemical residues are required to be routinely monitored in meat. Good farming and veterinary practice can prevent the contamination of meat with pharmaceutical substances, resulting in a low detection of drug residues through random sampling. An alternative approach is to target-monitor farms suspected of treating their animals with antimicrobials. The objective of this project was to assess, using a stochastic model, the efficiency of these two sampling strategies. The model integrated data on Swiss livestock as well as expert opinion and results from studies conducted in Switzerland. Risk-based sampling showed an increase in detection efficiency of up to 100% depending on the prevalence of contaminated herds. Sensitivity analysis of this model showed the importance of the accuracy of prior assumptions for conducting risk-based sampling. The resources gained by changing from random to risk-based sampling should be transferred to improving the quality of prior information.     

Efficiency of risk-based vs . random sampling for the monitoring of tetracycline residues in slaughtered calves in Switzerland

In all European Union countries, chemical residues are required to be routinely monitored in meat. Good farming and veterinary practice can prevent the contamination of meat with pharmaceutical substances, resulting in a low detection of drug residues through random sampling. An alternative approach is to target-monitor farms suspected of treating their animals with antimicrobials. The objective of this project was to assess, using a stochastic model, the efficiency of these two sampling strategies. The model integrated data on Swiss livestock as well as expert opinion and results from studies conducted in Switzerland. Risk-based sampling showed an increase in detection efficiency of up to 100% depending on the prevalence of contaminated herds. Sensitivity analysis of this model showed the importance of the accuracy of prior assumptions for conducting risk-based sampling. The resources gained by changing from random to risk-based sampling should be transferred to improving the quality of prior information.     

A survey of fish products for volatile N-nitrosamines

A study was undertaken to determine the levels of nitrate, nitrite and volatile N-nitrosamines of various fish products (halibut, salmon, cod, sole, ocean perch, scallops). The samples were analysed for five volatile nitrosamines, namely dimethyl-nitrosamine (DMN), diethylnitrosamine (DEN), dibutylnitrosamine (DBN), nitrosopyrrolidine (NPyr) and nitrosopiperidine (NPip), all of which are potent carcinogens. Both gas–liquid chromatographic (Coulson electrolytic conductivity detector, pyrolytic mode) and thin-layer chromatographic methods were used for estimating the levels of nitrosamines. The average level of nitrate was 8 part/10⁶ (range 0–94 parts/10⁶), and nitrite was present in traces only. Traces of DMN (3–12 parts/10⁹) were found in some uncooked (raw) fish. Increased levels of DMN (3–18 parts/10⁹) and traces of DEN (4–14 parts/10⁹) were observed after baking and frying, indicating formation of these compounds during cooking. None of the samples contained DBN, NPyr or NPip. In 10 out of 15 samples the identities and levels of DMN and DEN were confirmed by gas liquid chromatography–high resolution mass spectrometry.     

A comparative study of sampling techniques for monitoring carcass contamination

Four bacteriological sampling techniques i.e. the excision, double swab, agar contract and modified agar contact techniques were compared by sampling pig carcasses before and after chilling. As well as assessing the advantages and disadvantages of the techniques particular attention was paid to variation due to the effects of chilling. The agar contact technique cannot be used for determining the contamination of carcasses because too many plates became overcrowded with micro-organisms. Results obtained by the double swab and modified agar technique gave standard deviations which were significantly higher than those of the excision technique. This may indicate a superior repeatability of the excision technique. Statistical analysis of the results showed that chilling influenced the differences between sampling techniques. The excision technique is to be regarded as the most suitable in view of its high accuracy and precision. When the technique is used properly, carcass damage is only small or negligible.     

Design of a sampling plan to detect ochratoxin A in green coffee

The establishment of maximum limits for ochratoxin A (OTA) in coffee by importing countries requires that coffee-producing countries develop scientifically based sampling plans to assess OTA contents in lots of green coffee before coffee enters the market thus reducing consumer exposure to OTA, minimizing the number of lots rejected, and reducing financial loss for producing countries. A study was carried out to design an official sampling plan to determine OTA in green coffee produced in Brazil. Twenty-five lots of green coffee (type 7 - approximately 160 defects) were sampled according to an experimental protocol where 16 test samples were taken from each lot (total of 16 kg) resulting in a total of 800 OTA analyses. The total, sampling, sample preparation, and analytical variances were 10.75 (CV = 65.6%), 7.80 (CV = 55.8%), 2.84 (CV = 33.7%), and 0.11 (CV = 6.6%), respectively, assuming a regulatory limit of 5 µg kg^-1 OTA and using a 1 kg sample, Romer RAS mill, 25 g sub-samples, and high performance liquid chromatography. The observed OTA distribution among the 16 OTA sample results was compared to several theoretical distributions. The 2 parameter-log normal distribution was selected to model OTA test results for green coffee as it gave the best fit across all 25 lot distributions. Specific computer software was developed using the variance and distribution information to predict the probability of accepting or rejecting coffee lots at specific OTA concentrations. The acceptation probability was used to compute an operating characteristic (OC) curve specific to a sampling plan design. The OC curve was used to predict the rejection of good lots (sellers' or exporters' risk) and the acceptance of bad lots (buyers' or importers' risk).     

Comparison of manual and automatic sampling for monitoring ochratoxin A in barley grain

Automatic and manual sampling for ochratoxin A (OTA) in barley grain was compared under industrial conditions considering sampling uncertainty as well as practical and technical aspects. Ten tonnes of barley inoculated with Penicillium verrucosum were incubated until the OTA concentration reached approximately 15?μg?kg(-1) and sampled with manual and automatic sampling. A nested experimental design and ANOVA was used to estimate variance components from sampling, sample reduction, sample preparation and analysis. Manual sampling resulted in a high sampling uncertainty and OTA concentrations in aggregate samples ranged from 2 to 80?μg?kg(-1). When aggregate samples were formed by automatic sampling the uncertainty arising from nugget effects and spatial distribution was practically eliminated. Results from this study show that an automatic sampler mounted after a mixer or conveyer can provide representative samples of OTA from a moving stream of barley. Automatic sampling might present a practical and economical alternative to manual sampling for feed mill operators when monitoring low levels of mycotoxins in grain or other commodities. Despite careful precautions, sample preparation and analysis resulted in a relative uncertainty of ±40% (p?=?0.95), which was attributed to the sub-sampling following the two grinding steps. Size fractionation of the coarsely ground barley showed that 40% of the total amount of OTA was present in a small fraction of fine particles with a strong tendency to aggregate or stick to equipment and containers. Thus, in order to take advantage of the automatic sampling, it is crucial to apply an appropriate sub-sampling to prevent segregation of particles which may affect the OTA measurements.     

Modification of a colorimetric method for histamine analysis in fish meal

This study describes the modifications necessary to apply the colorimetric method for histamine detection in fish meal. Although the original colorimetric method works well with fish flesh, difficulties were observed during filtration of the homogenised sample and column separation when it was applied to fish meal. In this study, the reason for the problems encountered was studied by processing fish meal using different parts of fish. It was found that the problem was caused by the presence of bone in the sample, which suggested that calcium in bone reacted with potassium hydroxide (KOH) used to adjust pH during the experiment. This was confirmed by a chemical test reacting calcium carbonate with KOH solutions at different concentrations. The reaction was reversible in acidic conditions with trichloracetic acid (TCA) or hydrochloric acid (HCl). Several tests were applied before the filtration and neutralization stage of the method to solve the problems occurred. Centrifugation of the homogenised sample 20 min at 23 000 g and filtration of the aliquot after neutralisation gave the best result among the tests applied. The method was further modified by evaluating the suitable sample size, TCA volume and TCA concentration used as well as simplifying the moisture content application for fish meal. Other minor alterations were also suggested for both original and modified method at the preparation stage of diazotizing solution and absorption measurement.     

Comparison of manual and automatic sampling for monitoring ochratoxin A in barley grain

Automatic and manual sampling for ochratoxin A (OTA) in barley grain was compared under industrial conditions considering sampling uncertainty as well as practical and technical aspects. Ten tonnes of barley inoculated with Penicillium verrucosum were incubated until the OTA concentration reached approximately 15?µg?kg^?1 and sampled with manual and automatic sampling. A nested experimental design and ANOVA was used to estimate variance components from sampling, sample reduction, sample preparation and analysis. Manual sampling resulted in a high sampling uncertainty and OTA concentrations in aggregate samples ranged from 2 to 80?µg?kg^?1. When aggregate samples were formed by automatic sampling the uncertainty arising from nugget effects and spatial distribution was practically eliminated. Results from this study show that an automatic sampler mounted after a mixer or conveyer can provide representative samples of OTA from a moving stream of barley. Automatic sampling might present a practical and economical alternative to manual sampling for feed mill operators when monitoring low levels of mycotoxins in grain or other commodities. Despite careful precautions, sample preparation and analysis resulted in a relative uncertainty of ±40% (p?=?0.95), which was attributed to the sub-sampling following the two grinding steps. Size fractionation of the coarsely ground barley showed that 40% of the total amount of OTA was present in a small fraction of fine particles with a strong tendency to aggregate or stick to equipment and containers. Thus, in order to take advantage of the automatic sampling, it is crucial to apply an appropriate sub-sampling to prevent segregation of particles which may affect the OTA measurements.     

发酵肉制品中组胺含量测定方法的比较

分别采用液相色谱法、中国国标法和中国国标改进法3种方法测定发酵肉制品中组胺含量,并对检测结果进行比较,旨在建立一种准确且适用于测定发酵肉制品中组胺含量的测定方法。结果表明,3种方法的标准曲线都呈现良好的线性关系;液相色谱法的精密度最高,相对标准偏差1%,而中国国标法的精密度最差,相对标准偏差接近5%;液相色谱法和中国国标改进法加标回收率均高于90%以上,优于中国国标法,准确度满足试验要求。液相色谱法和中国国标改进法均能满足测定发酵肉制品中组胺含量的试验要求。     

Mathematical approach for sampling plan performance assessment for aflatoxin B1 in pistachios

According to the EU Regulation 165/2010, the level of aflatoxin B1 and total aflatoxins in pistachios must not exceed 8 μg/kg and 10 μg/kg, respectively. Due to the heterogeneous distribution of this contaminant, the performance of sampling plans highly depends on the way they are designed. So, the sampling plan to be used must be assessed thanks to an OC (Operating Characteristic) curve showing both consumer and producer risks. The first risk is the risk of authorizing pistachios for sale while the contamination level is above the threshold; whereas the second risk is the risk of rejecting a lot having a contamination level under the threshold.The method developed the use of early split contamination levels and incidence in individual pistachios to derive OC curves for various sampling plan designs for aflatoxin B1. Contamination levels in individuals were calculated from small sample contamination levels, thus having a negligible probability of containing more than one contaminated individual. Incidence levels of early split pistachios were derived for each harvest day. Indeed, early split nuts are dubious nuts that were considered to contain all the aflatoxin content found in a global sample. As their percentage increased along the harvesting period, it led to various contamination distributions in 10 kg samples. The EU sampling plan (Regulation 178/2010) was found to give a consumer risk with a probability of acceptance at 5% for a lot mean aflatoxin B1 concentration of 75.34 μg/kg and a producer risk with a probability of acceptance at 95% for a lot mean concentration of 1.62 μg/kg. Finally, the performance of several sampling plan designs was evaluated to demonstrate how to manipulate the number of samples to reduce misclassification of pistachio lots.     

Ultrasensitive flow-injection electrochemical method for determination of histamine in tuna fish samples

Histamine is a potentially hazardous compound and one of the major concerns in food chemistry. High amount of histamine may be found in food as a consequence of the use of poor quality raw materials, contamination and inappropriate conditions during food processing and storage. A novel method for the determination of histamine in flow-injection systems has been developed for use in seafood quality inspection and food quality control laboratories. The developed technique is very simple, precise, accurate, time saving and economic as compared to all of the previously reported methods. The effects of various parameters on the sensitivity of the method were investigated. The best performance was obtained with the conditions, pH value of 2.0, and sweep rate value of 40 V/s, accumulation potential of 900 mV and accumulation time of 0.4 s. In this work, we introduce a special computer based numerical method, for calculation of the analyte signal and noise reduction. The electrode response was calculated based on partial and total charge exchanges at the electrode surface after subtracting the background current from noise. The waveform potential consisting of potential steps for cleaning and accumulation of analyte, and potential ramp was applied on an Au disk microelectrode (with a radius of 12.5 μm). The method was linear over the concentration range of 1.1–5555 pg/ml (r = 0.998) with a limit of detection and quantification 0.35 and 1.16 pg/ml, respectively.     

分光光度法测定鱼罐头中组胺的方法改进

在GB/T 5009.45-2003国家标准方法的基础上对样品的前处理等过程进行了新的尝试,使样品前处理过程简单、快速,同时保证了方法的准确度和精密度.结果显示,在60℃水浴、30 min条件下,三氯乙酸的提取效果最佳;正戊醇提取过程采用旋涡后离心的方式代替了分液漏斗振摇,获得了较佳的提取效果;盐酸提取液改为1.0 mL,保证了标准系列与测定系列显色体系的一致性,同时保证了实验结果的准确度.     

Occurrence of histamine in canned tuna fish from Iran

Histamine fish poisoning is a significant public health and safety concern and also a trade issue. Histamine was investigated in canned tuna fish in Qazvin province from Iran by ELISA method. Histamine was detected in 29.37 % canned tuna fish samples. The overall mean level of histamine was 8.59 ± 14.24 ppm and the concentration was between 2.51 and 74.56 ppm. Except four samples (2.50 %) of 47 positive canned tuna fish samples, histamine content of other positive samples was in compliance with Food and Drug Administration (FDA) legislation (lower than 50 ppm). Most canned tuna fish contain histamine with high mean value was produced in summer (52.50 %) and spring (47.50 %) seasons, the mean levels of histamine were 6.30 and 12.62 ppm in these positive samples, respectively. The results of this study indicate that the most canned tuna fish produced in Qazvin province of Iran has histamine levels lower than the allowable limit suggested by FDA. Further studies should be carried out to investigate the presence of this toxin and other biogenic amines in different fish and sea food products.     

Application of modified atmosphere packaging on aquacultured fish and fish products: A review

The aquaculture industry has undergone a rapid and continuous growth during the last decade due to increased demands in seafood consumption and reduced pelagic fish production. The aquaculture sector can provide products with a consistent flow and quality standards to cover the market's needs. The modified atmosphere packaging (MAP) technique has evolved over the last two decades and many reports indicate its beneficial effect on many quality parameters during fish and shellfish preservation. The use of MAP can clearly offer an advantage to the safer distribution of quality aquacultured fishery products. This article summarizes most of the experimental data of packaging techniques applied (MAP, VP, various pretreatments and packaging materials) on aquacultured fish and fish products to provide a clear view of the potential for a future commercial use.