Detection of peanut (Arachis hypogaea) allergens in processed foods by immunoassay: Influence of selected target protein and ELISA format applied

Direct competitive and sandwich ELISA formats developed to determine Ara h1 and Ara h2 proteins were applied in the detection of peanut in model biscuits prepared with a commercial peanut butter as ingredient. The sandwich format for Ara h2 protein could detect the addition of 2.5% peanut butter, whereas the same format for Ara h1 could not detect 5% added peanut. Direct competitive formats for Ara h1 and Ara h2 proteins could detect the addition of 1% and 0.05% peanut butter, respectively. Therefore, competitive format for Ara h2 was selected to be evaluated by four laboratories, obtaining adequate results in term of repeatability and reproducibility. Results obtained indicate that processing decreased the level of extracted proteins and underestimated the amount of Ara h1 and Ara h2 proteins, the effect being more severe for Ara h1. The selection of the target protein and the ELISA format applied greatly influence the detection of peanut in processed foods.     

A practical test system for sensitive, rapid screening and authentication of peanut allergens in imported and exported food products in Chinese Customs

Proper food allergen labeling protects consumers with serious food allergies, such as peanut (Arachis hypogaea) allergies. Currently, there is no widely accepted standard peanut allergen detection protocol for use by Customs agencies, which could avoid trade disputes caused by improper labeling. Herein we developed a peanut allergen screening and confirmation system for sensitive, rapid identification of peanut allergen ingredients which used gold immunochromatography assay strips followed by confirmatory western blotting. Gold immunochromatography assay strips were prepared with polyclonal antibodies against total peanut proteins for preliminary peanut allergen screening in foods labeled peanut-free. Western blotting with Ara h1-specific monoclonal antibodies was performed to confirm the results to exclude false positive results. Of 285 food samples tested, 164 were labeled as containing peanut allergens. The gold immunochromatography assay determined that 116 were negative, in accordance with their original labels. Five samples were positive, which was not consistent with their labels. These 5 positive samples were subjected to western blotting confirmatory tests. Only one was confirmed to be positive. We reported this result to the manufacturer and suggested they change the product label. This system, which includes sequential classification, screening, confirmation and reporting steps, was useful for monitoring peanut contamination in imported and exported foods by Chinese Customs.     

油套管钢在甲酸盐-磷酸盐复配完井液中的腐蚀行为

采用高温高压模拟浸泡试验并结合多种表面分析手段,对超级13Cr马氏体不锈钢（油管钢）和P110碳钢（套管钢）在不同体积百分比的甲酸钾-焦磷酸钾复配完井液的腐蚀行为进行了研究。结果表明,对于超级13Cr马氏体不锈钢,复配完井液的主要腐蚀风险来源于其中的S元素夹杂,产物膜中S的富集是造成其耐蚀性降低的主要原因;而对于P110碳钢,高温下腐蚀产物厚且疏松,甲酸盐比例的增加可以缓解其表面腐蚀产物的沉积,从而提高产物膜的致密性,提高其高温耐蚀性。      

2205/Q235大面积双相不锈钢复合板性能分析

针对油田对集输管线用板材较高抗腐蚀性的要求,采用爆炸焊接技术,对2205双相不锈钢与碳钢Q235进行爆炸焊接,研制出了10 000 mm(长)×1 400 mm(宽)×14 mm(厚)大面积双相不锈钢复合板材,其中不锈钢层厚度为2 mm。检测结果表明:复合板材的剪切强度及其他力学性能均达到或超过标准要求;HIC试验和SSCC试验加载为72%Rt 0.5时均未出现任何裂纹;在H2S,CO2,C l-共存的气相腐蚀介质中,试样蚀速率为0.045mm/a;两种材料的复合界面SEM观察及元素分析表明,2205双相不锈钢与Q235完全实现了冶金结合。     

Inhibition of food poisoning and pathogenic bacteria by Lactobacillus plantarum strain 2.9 isolated from ben saalga, both in a culture medium and in food

The bacteriocinogenic strain Lactobacillus plantarum 2.9 isolated from the traditional pearl millet-based African fermented food ben saalga was tested for inhibition of food poisoning and pathogenic bacteria in MRS broth and in a malted millet flour slurry. In MRS broth, strain 2.9 completely eliminated Bacillus cereus, Escherichia coli O157:H7 and Salmonella enterica cells within 48 h incubation at 22–30 °C. A much lower inhibition was observed at 15 °C. The inhibitory effect of strain 2.9 on the above-mentioned target bacteria was corroborated in the malted millet flour slurry, reducing viable cell counts below detection levels after 8 h storage for B. cereus or after 24 h for S. enterica and 48 h for E. coli. An Enterobacter aerogenes strain was only moderately inhibited in the slurry. Results from the present study suggest that strain 2.9 could be used as starter culture to improve the microbiological safety of fermented ben saalga.     

Use of epifluorescence microscopy to assess the effectiveness of phage P100 in controlling Listeria monocytogenes biofilms on stainless steel surfaces

One source of foodborne listeriosis is related to a virulent strain established in the food-processing environment. We used direct epifluorescence microscopy (DEM) to evaluate the effectiveness of phage P100 in controlling Listeria monocytogenes biofilms on stainless steel surfaces, in wet conditions at room temperature. Biofilms that were allowed to develop for 72 h were subsequently treated with different concentrations of phage (5, 6, 7, and 8 log PFU/ml). L. monocytogenes was monitored up to 48 h, using both DEM and cultivation method. When L. monocytogenes was monitored using a cultivation method, the first significant reduction was observed after phage treatment with 7 and 8 log PFU/ml at 8 h. Subsequently, these treatments achieved undetectable levels of pathogen at 48 h, with a mean reduction of 5.29 log CFU/cm². Conversely, when samples were evaluated using DEM in treatments with 6, 7, and 8 log PFU/ml, although disaggregation of biofilms could be observed after 8 h, viable cells were still present up to 48 h (maximal reduction 1.5 log units). The phage titer remained stable or increased up to 2.59 log units during the study period. In conclusion, phage P100 may provide an adjuvant measure to control L. monocytogenes biofilm on stainless steel surfaces. However, phage treatment must be used in combination with other hygienization measures to increase efficacy. In this study, DEM was a good tool to quickly and accurately assess the real effect of phage P100 on L. monocytogenes biofilms.     

海洋腐蚀环境及船用不锈钢管选材备考(下)

从海水的成分和海水腐蚀因素对海洋腐蚀环境进行了分析,根据海洋船舶不锈钢管材的标准,分析并评估了海洋石油石化用不锈钢管在不同用途和环境下的选材思路,列举并分析了国内外海洋用不锈钢管的应用案例,最后对船舶用耐蚀合金的发展趋势进行了讨论。研究结果表明,Cl-孔蚀和缝隙腐蚀是海洋环境腐蚀危害的根本原因,304L钢不具备耐海洋腐蚀的性能,316L钢只能在一定环境和温度下在脱氧后的海水中使用;在自然海水中应用不锈钢管必须采用阴极保护措施;采油平台等油气生产作业船舶中各类管道的选材应先考虑其内部的油气介质成分及其腐蚀特征。     

海洋腐蚀环境及船用不锈钢管选材备考(上)

从海水的成分和海水腐蚀因素对海洋腐蚀环境进行了分析,根据海洋船舶不锈钢管材标准,分析并评估了海洋石油石化用不锈钢管在不同用途和环境下的选材思路,列举并分析了国内外海洋用不锈钢管的应用案例,最后对船舶用耐蚀合金的发展趋势进行了讨论。研究结果表明,Cl-孔蚀和缝隙腐蚀是海洋环境腐蚀危害的根本原因,304L钢不具备耐海洋腐蚀的性能,316L钢只能在一定环境和温度下在脱氧后的海水中使用;在自然海水中应用不锈钢管必须采用阴极保护措施;采油平台等油气生产作业船舶中各类管道的选材应先考虑其内部的油气介质成分及其腐蚀特征。     

Assessment of a handheld fluorescence imaging device as an aid for detection of food residues on processing surfaces

Contamination of food with pathogenic bacteria can lead to foodborne illnesses. Food processing surfaces can serve as a medium for cross-contamination if sanitization procedures are inadequate. Ensuring that food processing surfaces are correctly cleaned and sanitized is important in the food industry to reduce risks of foodborne illnesses and their related costs. A handheld fluorescence imaging device was assessed for detection of three types of food residues that have been associated with foodborne illness outbreaks, i.e. spinach leaf, milk, and bovine red meat, on two commonly used processing surfaces, i.e. high-density polyethylene and food grade stainless steel. Fluorescence excitation at 405 nm was supplied by 4 × 10 W light emitting diodes. Interchangeable optical filters were selected to optimise the contrast between the food residues and processing surfaces, using hyperspectral fluorescence imaging. The fluorescence imaging plus image analysis differentiated food residues from the processing surfaces more clearly than visual inspection in ambient lighting. This optical sensing device can be used to detect food fouling on food processing surfaces over relatively large areas, and has potential for use in the food industry as an aid for detection of specific food residues.     

Mathematical quantification of inactivation of Vibrio parahaemolyticus on two types of surface soiled with different substrates

Survivability of foodborne pathogens on food-processing surfaces is an important factor in understanding and quantifying bacterial transfer to foods (i.e. cross-contamination). This study examined the survival of Vibrio parahaemolyticus on two different surfaces in a laboratory-based simulation. V. parahaemolyticus was inoculated onto both polypropylene and stainless steel surfaces following contamination with saline solution (SS), tryptone soya broth (TSB), or seafood purge. V. parahaemolyticus remained viable on polypropylene for 10 days, but was undetectable within 24 h on the stainless steel surface. The survivability was similar on polypropylene in the presence of all contaminating substrates, as shown by data from the Weibull and biphasic models (adjusted-R² > 0.91). However, for stainless steel, SS and TSB prolonged the survival of V. parahaemolyticus to 144 and 120 h, respectively. Survivability data revealed a shoulder period in the first 4 h and a slight tailing effect at the end of the survival curve in the presence of seafood purge, which suggested that the biphasic model might be appropriate (adjusted-R² = 0.9442). These results indicate that the biphasic model may accurately estimate pathogen survival for cross contamination exposure. Integrating the survivability model into quantitative studies will help understand cross contamination.     

Adherence of cold-adapted Escherichia coli O157:H7 to stainless steel and glass surfaces

The effects of previous cold-induced cell elongation on adherence of Escherichia coli O157:H7 to glass slides and stainless steel surfaces was evaluated at 4 °C for ≤48 h. Planktonic E. coli O157:H7 with and without cold adaptation were prepared at 15 and 37 °C, respectively, and planktonic E. coli O157:H7 containing elongated (>4 ≤ 10 μm) and filamentous (>10 μm) cells were prepared at 6 °C. Despite morphological differences in planktonic E. coli O157:H7 preparations, all three cell types attached to a greater extent to glass than to the stainless steel surfaces. E. coli O157:H7 cells adapted to growth at 15 °C attached better to both glass and stainless steel surfaces (3.2 and 2.6 log cfu/cm², respectively) than cells of the other treatments at ≥24 h. Cells adapted at 6 °C attached to glass slides and stainless steel coupons at levels of 3.0 and 1.8 log cfu/cm², respectively, while E. coli O157:H7 cells grown at 37 °C attached to these surfaces at levels of 2.0 and 1.7 log cfu/cm², respectively. No further attachment of cells from any of the treatments was noted between 24 and 48 h at 4 °C. These results suggest that E. coli O157:H7 cells adapted at 6 °C–15 °C have greater potential to attach to food contact surfaces than those grown at higher temperature. The enhanced biofilm-forming ability of 6 °C or 15 °C-adapted, elongated and filamentous E. coli O157:H7 cells did not appear to be related to the greater entanglement of longer cells within biofilm matrices.     

A Bayesian network to optimise sample size for food allergen monitoring

Generally, sampling size is optimised considering a single specific constraint. However, for financial reasons, only one sample is usually defined and used to satisfy several objectives. It is therefore crucial to choose a sample that meets all the required objectives.This paper proposes an original method for optimising a sample plan to monitor allergen traces in products consumed by allergy sufferers. The proposed method, based on a Bayesian network, enables several different constraints to be considered within a single model and the integration of literature data on concentration levels of allergen traces in food. Moreover, the construction of a three-stage sampling plan took into account the consumption preferences of peanut allergy sufferers between products with or without labels on the presence of allergen traces, and between the categories and subcategories of products. This method was applied to data from the MIRABEL project which aims to assess risks related to peanut traces for French allergy sufferers.The results show how the model used all the available information and constraints to balance the total number of samples set at 900 for food categories/subcategories and labelling types. As required, the model favoured the most consumed product categories and subcategories. At the same time, it increased the number of samples when peanut concentration is low. This helps reduce the uncertainty on peanut concentrations in these products and consequently on risk estimation.In conclusion, the proposed method is a useful tool for public administrations, risk assessors and risk managers to improve sampling plans for monitoring allergen traces or other health hazards in food.     

Adhesion of Staphylococcus aureus on stainless steel treated with three types of milk

Staphylococcus aureus has the ability to adhere and to form biofilm on inert surface such as stainless steel commonly used in food industry. The biofilm formed on the surface of milk processing equipments could be a source of dairy products contamination. This contamination causes a food poisoning. In this paper the S. aureus adhesion on stainless steel treated by three types of milk (ultrahigh-temperature (UHT)-treated milk; UHT skimmed milk, UHT semi-skimmed milk) was investigated.Stainless steel was exposed to three types of milk with a different amount of fat component. Contact angles measurements were used to determine the surface physicochemical properties of substratum treated with the three milk products. The hydrophobicity and electron acceptor properties of stainless steel seem to be decreasing with the amount of fat component present in milk but its electron donor property increase with this component. The ability of S. aureus to adhere to stainless steel treated and untreated with milk was also examined. Treatment with the three types of milk reduces bacterial attachment. On treated substratum, the adhesion extent was affected by the type of milk and consequently by the amount of fat component. The lower and the higher adhesion were obtained when the steel was treated by the UHT semi-skimmed milk and UHT skimmed milk respectively. The correlation between physicochemical properties and S. aureus adhesion show that this latter was controlled by hydrophobicity and electron donor properties.The findings of this work can contribute to develop strategies for prevent S. aureus adhesion on stainless steel and biofilm formation. Also they could be taken into account in cleaning and disinfection procedures.     

Analysis of 140 pesticides from conventional farming foodstuff samples after extraction with the modified QuECheRS method

Pesticides in foodstuff are becoming a major issue due to their intensive use in agriculture. Thus an appropriate control of their residues in food samples has to be operated. In this study we analysed 105 pesticides with GC/SQ-MS and 46 pesticides with HPLC/IT-MS after extraction with the QuECheRS method in four matrices (grape, lemon, onion and tomatoes). For GC-amenable substances, the LOD and LOQ ranged from 0.4 to 48.2 μg/kg and from 1.2 to161 μg/kg, respectively. For HPLC-amenable substances, they varied from 1.0 to 115 μg/kg and from 3.3 to 382 μg/kg, respectively. With GC/MS, 61–82% of the substances showed a recovery in the range of 70–110% and 6–30 % presented a recovery higher than 110% at the 500 μg/kg fortification level. With HPLC/MS, 87–93% of the substances presented recoveries in the range of 70–110% at the 500 μg/kg fortification level compared to 78–85% at the 50 μg/kg fortification level. Lemon and onion showed poor recoveries but are known to be difficult matrices (high acidic and high sulfur content, respectively). The method was proved to be repeatable with RSD lower than 20% at 500 μg/kg and lower than 15% at 50 μg/kg with both devices.     

Evaluation of SICAN performance for biofouling mitigation in the food industry

Biological fouling in food industry leads to an increase in maintenance costs, decreases operational efficiencies and promotes food contamination leading to economic losses and the dissemination of foodborne pathogens. In order to maintain production efficiency and hygienic standards, cleaning in place (CIP) procedures are required. However, the existence of critical zones shielded from the main flow carrying the CIP disinfectants requires new strategies for reducing biofilm buildup and/or easy to clean surfaces. In this work, a Diamond-Like Carbon (DLC) coating modified by incorporation of silicon (a-C:H:Si or SICAN), was evaluated regarding bacterial adhesion, biofilm formation and cleanability. Assays included the natural flora present in industrial water (from a salad washing line) and Escherichia coli, one of the most persistent foodborne microorganisms.Results show that bacterial adhesion and biofilm formation on SICAN and stainless steel were similar, thus surface modification was not able to prevent biological fouling development. However, it was verified that after performing a cleaning protocol with chlorine, reduction of bacterial counts was much higher in SICAN (about 3.3 Log reduction) when compared to stainless steel (1.7 Log reduction). Although full biofilm recovery was observed on both surfaces 18 h after treatment, an operational window was identified for which processes with cleaning intervals of about 6 h could potentially use SICAN surfaces on critical areas (such as dead zones, crevices, corners, joints) and therefore operate at a much higher hygienic level than the one attained with stainless steel.     

Citric acid pretreatment for suppressing adhesion of major egg allergens to a stainless steel surface

Adhesion of proteins to solid surfaces can cause a number of problems in food manufacturing. In particular, a tiny amount of adherent allergenic proteins may pose a cross-contamination risk. To explore a strategy for suppressing adhesion of major egg allergens to stainless steel surfaces, the effect of citric acid pretreatment of stainless steel surfaces on the adhesion of ovalbumin and ovomucoid was studied under various conditions. Stainless steel powder was subjected to adhesion experiments after treatment with 50 mM citric acid solution, rinsing with water, and drying. Results from ovalbumin adhesion at 30 °C and pH 7.4 demonstrate that citric acid was more effective against ovalbumin adhesion than any univalent or divalent organic acid tested. This supports the idea that the suppression of adhesion is ascribed to the acid anions attaching to the stainless steel surface and yielding an effective negative surface charge. Citric acid pretreatment also suppressed the adhesion of ovalbumin at higher pH of 9.0 and temperature of 80 °C. The adhesion of ovomucoid was also suppressed at both 30 and 80 °C by citric acid pretreatment. These results suggest that the citric acid pretreatment is effective against the adhesion of major egg allergens to stainless steel surfaces.     

Loop-mediated isothermal amplification (LAMP) coupled with bioluminescence for the detection of Listeria monocytogenes at low levels on food contact surfaces

A commercial loop-mediated isothermal amplification (LAMP) based system with bioluminescence, named as 3M™ Molecular Detection Assay (MDA), was validated for the detection of Listeria monocytogenes (3-strain cocktail) at low levels (10⁰, 10¹, 10² CFU/100 cm²) inoculated on stainless steel (SS) and polyethylene (PE) surfaces, with and without (w/o) organic load (OL) of cold-smoked salmon homogenate by comparing with a standard ISO method as reference. The results of this study revealed that a commercial LAMP-based method performed equally effective compared with ISO method at inoculum levels of 10⁰ and 10²/100 cm², showing 100% specificity and sensitivity, respectively. At 10¹ CFU/100 cm², a slight reduction in the effectiveness of LAMP-based method was observed most likely due to the use of single enrichment step in the procedure of LAMP-based method. The LAMP-based method was shown to be rapid and reliable detection technique for L. monocytogenes present at low numbers on food processing surfaces, regardless of organic residues, and can be applicable in seafood industry.     

Effects of home preparation on pesticide residues in cabbage

Experiment was carried out to evaluate the pesticides (chlorpyrifos, p,p-DDT, cypermethrin, chlorothalonil) residue levels in cabbage in the process of home preparation by washing with different concentrations of acetic acid and sodium chlorine, and tap water, preserving in refrigerator, and stir-frying for different time. Results showed that washing by tap water and/or detergent solution for cooking are necessary to decrease the concentration of pesticide residues in cabbage. Washing with acetic acid solutions (at 10% concentration for 20 min) caused 79.8%, 65.8%, 74.0% and 75.0% loss of the above pesticides, respectively. Washing with NaCl solutions (at 10% concentration for 20 min) produced 67.2%, 65.0%, 73.3% and 74.1% loss, respectively, and washing by tap water (for 20 min) were 17.6%, 17.1%, 19.1% and 15.2% loss, respectively. The reductions due to the refrigeration (for 48 h) were 3.4%, 2.6%, 3.1% and 3.6%, respectively, and those due to the stir-frying (for 5 min) were 86.6%, 67.5%, 84.7% and 84.8%, respectively. The data indicated that washing by detergent solutions and stir-frying of cabbage are the most effective home preparations for the elimination of pesticide residues.     

Lactobacillus sakei 1 and its bacteriocin influence adhesion of Listeria monocytogenes on stainless steel surface

Listeria monocytogenes is of particular concern for the food industry due to its psychrotolerant and ubiquitous nature. In this work, the ability of L. monocytogenes culturable cells to adhere to stainless steel coupons was studied in co-culture with the bacteriocin-producing food isolate Lactobacillus sakei 1 as well as in the presence of the cell-free neutralized supernatant of L. sakei 1 (CFSN-S1) containing sakacin 1. Results were compared with counts obtained using a non bacteriocin-producing strain (L. sakei ATCC 15521) and its bacteriocin free supernatant (CFSN-SA). Culturable adherent L. monocytogenes and lactobacilli cells were enumerated respectively on PALCAM and MRS agars at 3-h intervals for up to 12 h and after 24 and 48 h of incubation. Bacteriocin activity was evaluated by critical dilution method. After 6 h of incubation, the number of adhered L. monocytogenes cells in pure culture increased from 3.8 to 5.3 log CFU/cm² (48h). Co-culture with L. sakei 1 decreased the number of adhered L. monocytogenes cells (P < 0.001) during all sampling times with counts lower than 3.0 log CFU/cm². The CFNS-S1 also led to a significant and similar reduction in culturable adhered L. monocytogenes counts for up to 24 h of incubation, however after 48 h of incubation, re-growth of L. monocytogenes number of adhered cells was observed, likely due to lack of competition for nutrients. L. sakei ATCC 15521 or its supernatant (CFNS-SA) did not reduce the number of adhered L. monocytogenes cells on stainless steel surface and from 6 h of incubation, listerial counts were between 4.3 and 4.5 log CFU/cm². These results indicate that L. sakei 1 and its bacteriocin sakacin 1 may be useful to inhibit early stages of L. monocytogenes adherence to abiotic surface.     

Cr12MoV膨胀锥在管材膨胀试验中的应用

膨胀锥是膨胀工具的核心部分,对膨胀管技术的应用和发展意义重大.选用模具钢Cr12MoV为基材,设计加工了小锥度(6°)的膨胀锥,采用自上而下的膨胀工艺对J55套管和316L 不锈钢管进行径向膨胀.试验结果表明:经过1 020℃淬火+160℃低温回火处理后,Cr12MoV膨胀锥满足工作要求,并顺利完成对J55套管和316L不锈钢管的径向膨胀;2种管材的平均膨胀率分别为9.33％和9.05％,其长度减小幅度分别约为4.4％和3.6％,J55套管的回弹率要略大于316L不锈钢管.