Different Types Of Food Samples Research Articles

Development of an ultrasensitive electrochemical aptasensor based on aptamer/rGO/SPGE for the detection of Botulinum neurotoxin A (BoTN/A) in food samples

Consumption of Botulinum neurotoxin A (BoTN/A) contaminated foods has increased the public health issues which necessitates the development of rapid and simple diagnostic tools for their sensitive detection. Electrochemical aptasensors can replace existing biosensors and traditional methods of BoTN/A detection in foods. These aptasensors are simple, quick response, economic, precise, sensitive, accurate and reproducible. In the present study, an electrochemical aptasensor was constructed by immobilizing BoTN/A specific aptamer and reduced graphene oxide (rGO) onto screen printed gold electrode (SPGE) for the detection of BoTN/A in spiked food samples. The specificity of this aptasensor was achieved by conjugating BoTN/A specific aptamer on rGO/SPGE. Test sample containing BoTN/A form aptamer-BoTN/A complex onto SPGE which was directly proportional to BoTN/A concentration. Formation of aptamer-BoTN/A complex reduced the surface of working SPGE for redox reactions. Thus decreased the current peaks that was taken as measuring signal of BoTN/A in test food sample. BoTN/A aptasensor showed optimum response at pH 6.5 and 30 °C temperature. The responsetime of BoTN/A/aptamer/rGO/SPGE was 6 s. In optimum conditions aptamer/rGO/SPGE BoTN/A aptasensor exhibited wide linearity ranges from 1-100 pM and 1 pM limit of detection (LOD). The analytical recoveries of aptamer/rGO/SPGE BoTN/A aptasensor at 5 pM and 10 pM BoTN/A were 98.5 % and 99.8 % respectively. The proposed aptasensor showed unique sensitivity, reproducibility and accuracy. Moreover, aptamer/rGO/SPGE aptasensor was used for the detection of BoTN/A in five different types of food samples.

A wearable gloved sensor based on fluorescent Ag nanoparticles and europium complexes for visualized assessment of tetracycline in food samples.

The abuse of tetracycline antibiotics leads to accumulating residues in the human body, seriously affecting human health. Establishing a sensitive, efficient, and reliable method for qualitative and quantitative detection of tetracycline (TC) is necessary. This study integrated silver nanoclusters and europium-based materials into the same nano-detection system to construct a visual and rapid TC sensor with rich fluorescence color changes. The nanosensor has the advantages of a low detection limit (10.5nM), high detection sensitivity, fast response, and wide linear range (0-30μM), which can meet the analysis requirements of different types of food samples. In addition, portable devices based on paper and gloves were designed. Through the smartphone's chromaticity acquisition and calculation analysis application (APP), the real-time rapid visual intelligent analysis of TC in the sample can be realized, which guides the intelligent application of multicolor fluorescent nanosensors.

A new efficient sample pooling procedure for qualitative screening analysis. Application to the detection of salmonella spp and nut allergen by PCR

Foodborne pathogens and allergens are a major concern for public health that determines food safety policy, and their screening could be improved using pooled samples.The purpose of this paper is to propose a cost-effective and accurate pooling strategy for the unambiguous identification of foodborne pathogens and allergens, enabling laboratories to redouble testing capacity while saving time and making optimal use of resources.Although a variety of pooling algorithms have been used in different fields, the strategy suggested here is a logical analysis of sample pooling aimed at qualitative analytical screening problems. It involves, on the one hand, a design matrix to make the pooled samples, which is a supersaturated-based design, particularly, a half-fraction of a Plackett-Burman. On the other hand, a logical (non-algebraic) modeling of the problem, as well as a logical procedure for the identification of the original positive samples, is included.Regarding the efficiency of the proposal, it is higher than that of other pooling algorithms, with an expected number of tests per individual sample ranging between 0.10, for a prevalence below 1%, and 0.59, for a prevalence above 10%. In terms of accuracy, the pooling sensitivity reaches 0.9697 for a sensitivity of the analytical test about 0.99, while pooling specificity ranges from 0.9872 to 0.9999, provided that the sensitivity and specificity of the analytical test are equal to or greater than 0.90.This pooling strategy has been applied to the detection of salmonella spp and nut allergen with complete identification of the contaminated samples. Furthermore, based on the EU reported food samples contaminated with salmonella, a comprehensive comparison between individual sampling and the applied pooling strategy has been conducted. For the specific case of salmonella, detailed calculations have been made on the expected efficiency gains induced by this pooling methodology for different types of food samples monitored in the EU.

Identification of new serovar-specific detection targets against salmonella B serogroup using large-scale comparative genomics

Salmonella serotyping is a critical step for the identification of pathological isolates in humans and animals. Whole-genome analysis is a proven method for Salmonella serovars identification. In this study, we analysed 1668 genomic sequences of 23 serogroup B serovars and 129 genomic sequences of 80 non-target serovars to detect serovar-specific molecular targets for serogroup B (O:4 epitopes). Serogroup B is the most common serogroup found in China, whose presence is increasing in recent years. We identified five, eight, one, and seven new serovar-specific genes for Indiana, Derby, Typhimurium, and Agona serovars, respectively. We then designed specific PCR primer sets for these genes to validate our results. All target Salmonella serovars could be detected successfully by PCR in different types of food samples. The analytical sensitivity of PCR for 19 out of 21 pairs of primers was 101–103 CFU/mL and 102–105 CFU/g in pure cultures of the bacteria and artificially contaminated fresh pork samples, respectively. Furthermore, we performed a functional analysis of the newly-identified serovar-specific genes. We found that the function was unknown for most of the genes, although for some of them we were able to identify their generic functional categories (membrane protein genes and secreted proteins genes). Our findings revealed that whole-genome analysis is a valuable tool to identify new serovar-specific targets, which could be used to develop rapid and accurate molecular detection methods and provide additional information about different Salmonella serogroup B serovars.

Prevalence, virulence, antimicrobial resistance, and molecular characterization of fluoroquinolone resistance of Vibrio parahaemolyticus from different types of food samples in China

Vibrio parahaemolyticus is the leading cause of foodborne bacterial poisoning in China. The aim of this research is to conduct a study on the prevalence, virulence, and antimicrobial resistance of V. parahaemolyticus from different types of food samples in 12 different cities of China. Since fluoroquinolones are the major choice of treatment for V. parahaemolyticus infections, the genetic basis for fluoroquinolone resistance in V. parahaemolyticus were also investigated. V. parahaemolyticus was detected in 163 of the 784 food samples collected from 12 different cities in China, resulting in a prevalence of 20.79%. The prevalence of V. parahaemolyticus in ready-to-eat (RTE) food (4.96%) was much lower than those of shrimp (32.62%) and fish (22.00%). Virulence gene screening showed that 44 (27.00%) V. parahaemolyticus strains carried at least one virulence gene. Four isolates from shrimp and three isolates from fish contained both the virulence genes tdh and trh. In addition, the trh was firstly detected in one isolate collected from RTE food. All isolates exhibited relatively high resistance rates to ampicillin (82.21%), gentamicin (19.63%), and tetracycline (14.11%), while <10% of strains were resistant to ciprofloxacin (4.91%), levofloxacin (4.91%), and tetracycline (4.29%). Eight fluoroquinolone-resistant V. parahaemolyticus were selected to determine the molecular basis for fluoroquinolone resistance. These eight isolates belonged to three different types according to enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR). A Ser83Ile substitution in GyrA was deteted in seven fluoroquinolone-resistant strains, except V209 which harbored a Ser83Phe substitution in GyrA. Moreover, A Ser85Leu substitution in ParC was found in five isolates (V52, V53, V61, V163, and V209). Plasmid-mediated quinolone resistance (PMQR) genes were detected in all eight fluoroquinolone-resistant V. parahaemolyticus strains. This is the first report of Ser83Phe substitution in GyrA, qnrD and qnrS1 in V. parahaemolyticus. The information generated in this study will provide valuable information for risk assessment of V. parahaemolyticus infections and future control of antibiotic-resistant V. parahaemolyticus species in China.

Comparison of Organic and Conventional Food and Food Production Part V: Human Health – Pesticide Residues

The present report is based on data from the 2010 EFSA Report on pesticide residues in food, the Norwegian monitoring programmes 2007-2012 and data from peer reviewed literature and governmental agencies. It is a challenge to perform quantitative estimates and comparative studies of residue levels due to large variation in the measured levels, and the large number of different pesticides present in the samples. Thus, the focus is on the frequency of observed contaminations in relation to regulatory limits and to present examples to illustrate the variation in residue values and number of detected substances. &#x0D; Pesticide residues in conventional and organic products:&#x0D; Of the 12,168 samples (plant- and animal products) in the 2010 EU-coordinated programme, 1.6% exceeded the respective maximum residue level (MRL) values, and 47.7% had measurable residues above the limit of quantification (LOQ), but below or at the MRL. Of the 1168 samples analysed in Norway in 2012 (from both imported and domestic products), 1.9% exceeded MRL and 53% contained measurable pesticide residues. Direct comparison of these values is however not possible, since they contain different types of food samples, and are analysed for a different number of pesticides.&#x0D; When organic and conventional samples from fruit, vegetables and other plant products in the 2010 EU-coordinated programme were compared, 4.2% of the conventional and 1.0% of the organic samples exceeded the MRL values, while 43.2% of the conventional and 10.8% of the organic samples had measurable residues below or at the MRL value. Most of the pesticide residues detected in organic samples are not permitted for use in organic farming. &#x0D; Of the 624 organic samples analysed in Norway 2007 - 2012, 0.2% (one sample) had residues exceeding MRL, while measurable residues were detected in 1.8% of the samples (11 samples).&#x0D; Conventional products were often found to contain different pesticides while most organic samples were found to contain few or only one type of pesticide. &#x0D; Lack of data on pesticide residue levels of organic samples in the EU-coordinated programme, and few Norwegian samples do not allow for a quantitative comparison of pesticide residue levels in organic and conventional samples. Comparative estimation of pesticide residues faces a number of challenges and uncertainties. However, it seems unquestionable based on available data that organic plant products contain fewer and substantially lower amounts of pesticide residues than conventional products.&#x0D; Health risk associated with pesticide residues:&#x0D; The general level of pesticide residues in both conventional and organic food is low, and well below what is likely to result in adverse health effects. This conclusion is based on the comparison of estimated dietary exposure with toxicological reference values i.e. acceptable daily intake (ADI) for chronic effects, and acute reference dose (ARfD) for acute effects. The finding of pesticide residues that exceeds established regulatory limits in a minority of tested samples is not considered to represent a health risk.&#x0D; When dietary exposure that was estimated in six different food commodities in the 2010 EUcoordinated programme was compared with their relevant reference values, EFSA concluded that for 79 of 18243 conventionally grown fruit and vegetable samples, a short-term acute consumer health risk could not be excluded. The conclusion was based on the exceeding of ARfD. None of these 79 samples were organic. It is important to also consider that the exceeding of the acute reference value only occurred in 0.4% of the samples and that the scenario used for acute intake assessment is conservative, suggesting that the toxicological implications are limited. This is also reflected in the chronic exposure assessment, where none of the samples were found to exceed the toxicological reference value ADI. &#x0D; Dietary exposure assessments on the basis of Norwegian samples of apples, tomatoes, carrots, strawberries and lettuce did not show an exceeding of any toxicological reference value. &#x0D; Combined exposure and cumulative risk assessment of pesticide residues:&#x0D; No generally accepted methodology is at present established for cumulative risk assessment of combined exposure to pesticide residues. Available data suggest however that combined exposure is not likely to result in increased human health risk.

Monitoring of genetically modified food on the Czech food market and a cross-country comparison

The presence of genetically modified organisms (GMOs) was analysed in food samples from the Czech food markets. Four different types of food samples (soya beans, soya bean products, maize flour, and rice) were collected at twelve places in four terms in the years 2008–2013. It represents a total 1152 food samples. Soya and maize were chosen, because these are the major transgenic crops grown worldwide. Increased cultivation of GM rice in China, India, Indonesia, and the Philippines has been observed. Polymerase chain reaction-based methods were applied to detect GMOs. GMOs were detected in 107 samples (9.3%). The results show that in food from the Czech food market GMOs mainly in maize flour and rice were found. GM maize was detected in 63 (21.9%) maize flour samples. Maize lines MON810, NK603, and Bt176 were detected in 14 (22%), 9 (14%), and 1 (1.6%) maize flour samples, respectively. Unauthorised GM rice was detected in 39 (13.5%) rice samples. Unauthorised rice Bt63 was detected in one sample of rice. Roundup Ready soya was detected in 4 (1.4%) soya bean samples and in 1 (0.35%) soya product sample. These results were compared with results of the world´s studies.

음식물의 악취 황화합물 발생특성 조사: 계란, 우유, 고기통조림, 딸기에 대한 사례 연구

In this study, the emission patterns of reduced sulfur compounds (RSC) were investigated using four different types of food samples (boiled egg, milk, canned meat and strawberry) between fresh and decaying stages. To this end, the concentrations of RSCs were measured at storage days of 0, 1, 3, 6, and 9 under room temperature. Four sulfur compounds (, , DMS and DMDS) were selected as target compounds along with two reference compounds ( and ). Their concentrations were quantified using GC-PFPD equipped with thermal desorption (TD) system. The boiled egg showed the highest concentration of (3,655 ppb) at D-1, while reached its maximum value of 64.4~78.5 ppb after 3 days. In milk samples, concentration of , DMS, and DMDS went up to 487, 16.3, and 578 ppb, respectively with the progress of decay (D-9). In case of canned meat, concentration of and peaked in the beginning (D-0) such as 345 and 66.6 ppb. In case of strawberry, and DMDS showed the maximum concentrations 135 and 50.5 ppb at D-1, respectively. The olfactometry dilution-to-threshold (D/T) ratio by air dilution sensory (ADS) test showed similar patterns when sum of odor intensity (SOI) was derived via conversion of odorant concentration data. The results of this study confirm that the time of strong RSC emissions is distinguished for each food type between fresh (e.g., strawberries) and decaying conditions (e.g., milk).

Detection of Salmonella enterica serovar Enteritidis using real time PCR, immunocapture assay, PNA FISH and standard culture methods in different types of food samples

Several methods for the rapid and specific detection of Salmonella in food samples have been described. Here, we compare 4 of those methods in terms of assay time, procedure complexity, detection limit, sensitivity, specificity and accuracy. Milk, eggs and mayonnaise samples were artificially contaminated with Salmonella enterica serovar Enteritidis cell concentrations ranging from 1×10−2 to 1×102CFU per 25g or ml of food. Samples were then pre-enriched and analyzed by either: i) real-time PCR, using the iQ-Check Salmonella kit; ii) immunocapture, using the RapidChek SELECT Salmonella; iii) a peptide nucleic acid fluorescence in situ hybridization (PNA FISH) method and iv) the traditional bacteriological method ISO 6579:2002. All methods were able to detect Salmonella in the different types of food matrixes and presented a similar detection level of 1CFU per 25g or ml of food sample. The immunocapture and the PNA FISH methods proved to be very reliable, as their results were 100% in agreement with the ISO method. However, real-time PCR presented a significant number of false positives, which resulted in a specificity of 55.6% (CI 95%, 31.3–77.6) and an accuracy of 82.2% (CI 95%, 63.2–91.4) for this method. Sensitivity was 100% since no false negative results were observed. In conclusion, the implementation of these molecular techniques, mainly the immunocapture and PNA-FISH methods, provides a reliable and less time-consuming alternative for the detection of Salmonella spp. in food samples.

Occurrence and Characterization of Shiga Toxin–ProducingEscherichia coliin Raw Meat, Raw Milk, and Street Vended Juices in Bangladesh

The major objective of this study was to investigate the prevalence of Shiga toxin (Stx)-producing Escherichia coli (STEC) in different types of food samples and to compare their genetic relatedness with STEC strains previously isolated from animal sources in Bangladesh. We investigated a total of 213 food samples, including 90 raw meat samples collected from retail butcher shops, 20 raw milk samples from domestic cattle, and 103 fresh juice samples from street vendors in Dhaka city. We found that more than 68% (n = 62) of the raw meat samples were positive for the stx gene(s); 34% (n = 21) of buffalo meats and 66% (n = 41) of beef. Approximately 10% (n = 2) of the raw milk and 8% (n = 8) of the fresh juice samples were positive for stx. We isolated STEC O157 from seven meat samples (7.8%), of which two were from buffalo meats and five from beef; and no other STEC serotypes could be isolated. We could not isolate STEC from any of the stx-positive raw milk and juice samples. The STEC O157 isolates from raw meats were positive for the stx(2), eae, katP, etpD, and enterohemorrhagic E. coli hly virulence genes, and they belonged to three different phage types: 8 (14.3%), 31 (42.8%), and 32 (42.8%). Pulsed-field gel electrophoresis (PFGE) typing revealed six distinct patterns among seven isolates of STEC O157, suggesting a heterogeneous clonal diversity. Of the six PFGE patterns, one was identical and the other two were ≥90% related to PFGE patterns of STEC O157 strains previously isolated from animal feces, indicating that raw meats are readily contaminated with fecal materials. This study represents the first survey of STEC in the food chain in Bangladesh.

Determination of melamine in milk-based products and other food and beverage products by ion-pair liquid chromatography–tandem mass spectrometry

This paper describes a fast method for the sensitive and selective determination of melamine in a wide range of food matrices, including several milk-based products. The method involves an extraction with aqueous 1% trichloroacetic acid before the injection of the 10-fold diluted extract into the liquid chromatography–electrospray tandem mass spectrometry (LC–ESI-MS/MS) system, using labelled melamine as the internal standard. As melamine is present in aqueous media in the cationic form, the chromatographic separation in reversed-phase LC requires the use of anionic ion-pair reagents, such as tridecafluoroheptanoic acid (THFA). This allows a satisfactory chromatographic retention and peak shape in all the types of food samples investigated. The method has been validated in six food matrices (biscuit, dry pasta and four milk-based products) by means of recovery experiments in samples spiked at 1 and 5 mg kg −1. Average recoveries ( n = 5) ranged from 77% to 100%, with excellent precision (RSDs lower than 5%) and limits of detection between 0.01 and 0.1 mg kg −1. In addition, accuracy and robustness of the method was proven in different soya-based matrices by means of quality control (QC) sample analysis. QC recoveries, at 1 and 2.5 mg kg −1, were satisfactory, ranging from 79% to 110%. The method developed in this work has been applied to the determination of melamine in different types of food samples. All detections were confirmed by acquiring two MS/MS transitions (127 > 85 for quantification; 127 > 68 for confirmation) and comparing their ion intensity ratio with that of reference standards. Accuracy of the method was also assessed by applying it to a milk-based product and a baking mix material as part of an EU proficiency test, in which highly satisfactory results were obtained.

The use of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of toxic and essential elements in different types of food samples

This paper describes a simple method for the determination of sixteen elements in food samples by using inductively coupled plasma spectrometry (ICP-MS). Prior to analysis, 100–250 mg of powdered food samples were accurately weighed into a Teflon digestion vessel. Then, 4 ml of 20% v/v concentrated nitric acid and 2 ml of hydrogen peroxide were added. Decomposition of samples was carried out in a microwave digestion system. In order to verify the accuracy and precision of the proposed method, five Standard Reference Materials from the National Institute of Standards and Technology (NIST) (Whole Egg Powder RM 8415, Rice Flour SRM 1568a, Typical Diet SRM 1548a, Wheat Flour SRM 1567a and Bovine Muscle Powder RM 8414) were analyzed. Additional validation data are provided based on the analysis of 18 different types of food samples by the proposed method and using comparative methods with AAS as the detector.

Assessing the Diet of the Black Skimmer Through Different Methodologies: Is the Analysis of Pellets Reliable?

Abstract Two different types of food samples from the Black Skimmer (Rynchops niger) were collected during the non-breeding season: spontaneous regurgitations and pellets. These two samples were analyzed and differed in the number of taxonomic categories represented, the number of fish prey species found and in the estimated size of fish prey. However, key prey were the same and well represented in both types of samples, suggesting that both sources gave accurate information, at least for the main items. Given that collecting pellets involves little effort and low disturbance to the birds, the value of the analysis of pellets to monitor long-term dietary changes in the Black Skimmer and other seabird species of similar size and diet is considerable. Correction factors are proposed to overcome underestimation of the total length and mass of some fish prey species remains found in pellets.

Detection of Staphylococcal Enterotoxin B in Spiked Food Samples

Contamination of food with infectious agents, intentional or not, is a global concern with far-reaching economic and social impact. Staphylococcal enterotoxins are a major cause of food poisoning, but most methods for the identification of these agents in food require extensive pretreatment or concentration of the sample prior to analysis. The array biosensor was developed as a portable device for the simultaneous analysis of multiple complex samples for multiple targets with minimal sample preparation. In this study, we use an array biosensor to expand and improve on a staphylococcal enterotoxin B (SEB) assay with the ultimate intent of incorporating testing for SEB into a battery of sensitive and convenient assays for food safety validation. In addition to buffer studies, six different types of food samples, including beverages, homogenates of fruit and meat, and carcass washings, were spiked with SEB, incubated for at least 2 h to permit antigen sequestration, and assayed. For all samples, there were differences in fluorescence intensity, but 0.5 ng of SEB per ml could be detected in <20 min with little if any pretreatment and no sample preconcentration.

Bias Associated with Diet Samples in Audouin's Gulls

We analyzed five different types of food samples from Audouin's Gull (Larus audouinii), collected during the breeding seasons of 1994 and 1995 at its two main breeding colonies, the Ebro Delta and the Chafarinas Islands. These food samples included spontaneous regurgitates, dry boli containing partially digested food, food remains, pellets, and prey identified during direct observations of chick provisioning. We compared estimates of biomass, levels of taxonomic determination allowed by each kind of food sample, and the associated potential biases to assess which sampling method provides the best estimate of diet in gulls. Regurgitates allowed identification of most prey to species level and reliable biomass estimates, but their collection was time-consuming and invasive. Dry boli provided almost the same information as regurgitates at order level and were easy to collect. However, both underestimated soft-bodied prey and prey with large, hard parts. Food remains provided an estimate of diet composition that was highly biased towards prey with large distinctive hard parts. However, food remains were a good complement to dry boli, enhancing biomass estimates for food items that had a good relationship of weight and linear measurements of prey..hard parts. Direct observation allowed identification of prey only to upper taxonomic categories, and is useful when only a broad categorization of prey types is required. Pellets showed important biases towards fish with robust otoliths, and inaccurate conversion to biomass, but they can be useful for monitoring variations in the consumption of certain prey items. Several factors such as time spent collecting, sample availability, disturbance to animals, and the status of the species studied need to be considered when deciding on a method of diet assessment sampling.