免疫学技术在食品过敏原检测中的应用

食品过敏原可引起机体产生过敏反应,严重危害人类健康及生命安全。目前食品包装上过敏原信息标注规 范尚不完善,因此食品过敏原检测技术对于预防含有过敏原食品进入流通领域,减少过敏事件发生至关重要。本文 综述了免疫学检测技术在食品过敏原检测中应用,并展望了其未来的发展趋势。     

Biogas production from catch crops: Increased yield by combined harvest of catch crops and straw and preservation by ensiling

The combination of catch crop cultivation with its use for biogas production would increase renewable energy production in the form of methane, without interfering with the production of food and fodder crops. The low biomass yield of catch crops has been shown as the main limiting factor for using these crops as co-substrate in biogas plants, since the profit obtained from the sale of methane barely compensates the harvest costs. Therefore, a new agricultural strategy to harvest catch crops together with the residual straw of the main crop was investigated, in order to increase the biomass and the methane yield per hectare. Seven catch crops harvested together with stubble from the previous main crop were evaluated. The effects of stubble height, harvest time and ensiling as a storage method for the different catch crops/straw blends were studied. Biomass yields as TS ranged between 3.2 and 3.6 t ha⁻¹ y⁻¹of which the catch crop constituted around 10% of the total biomass yield. Leaving the straw on the field until harvest of the catch crop in the autumn could benefit methane production from the straw both due to increased biomass yield and an increased organic matter bioavailability of the straw taking place on the field during the autumn months. Ensiling as a storage method could be feasible in terms of energy storage and guaranteeing the feedstock availability for the whole year. This new agricultural strategy may be a good alternative for economically feasible supply of catch crops and straw for biogas production.     

Distribution,stability, and protein interactions of Aflatoxin M1 in fresh cheese

Aflatoxin M₁ (AFM₁), a metabolite resulting from the hepatic metabolism of aflatoxin B₁, is a potential carcinogen that can be found in milk, cheese, and others dairy products. In this work, we aimed to elucidate the distribution and fate of AFM₁ in fresh cheese and whey during cheese manufacturing and storage as well as the level of interaction of this toxin with various milk, cheese, and whey proteins. Additionally, we analyzed the in vitro behavior of casein, α-lactalbumin, β-lactoglobulin, bovine serum albumin (BSA), lactoferrin, and mixtures thereof, with a fixed concentration of AFM₁ after covalent crosslinking. Our results show that up to 70% of the AFM₁ levels present in milk spiked with 0.5 and 1.5 μg L⁻¹ are released in whey during fresh cheese manufacturing. The whey and milk proteins with more AFM₁ molecules bound were α-lactalbumin and casein, with 88% and 81%, respectively. We also observed a substantial decrement in AFM₁ concentration during ripening that correlated inversely with plate counts of lactic acid bacteria and directly with the whey-draining process that occurs during fresh cheese maturation or storage. This knowledge may serve as a basis for interventions in the dairy industry aiming to increase the security of cheese and other dairy products.     

盐酸可乐定人工抗原的合成及鼠源多抗血清ELISA鉴定

目的：获得敏感性高,特异性强的新型瘦肉精盐酸可乐定（Clonidine hydrochloride,CLO）鼠源多抗血清。方法：以CLO的衍生物盐酸阿可乐定（Apraclonidine hydrochloride,ACLO）为半抗原,采用戊二醛法将ACLO分别与牛血清白蛋白（Bovine serum albumin,BSA）和鸡卵清蛋白（Ovalbumin,OVA）偶联,合成免疫抗原CLO-BSA和包被抗原CLO-OVA。采用紫外扫描和聚丙烯酰胺凝胶电泳鉴定其偶联效果后,免疫BALB/c小鼠,制备多抗血清。利用间接ELISA和间接竞争ELISA鉴定其免疫学特性。结果：合成的人工抗原免疫效果较好,所获小鼠多抗血清效价均达到1∶12 800以上,其中3号小鼠敏感性最好,半数抑制质量浓度（IC₅₀）为82.75 ng/mL,与其他几种常见的瘦肉精类药物的交叉反应率均小于0.9%,特异性良好。结论：通过戊二醛法成功合成了高免疫原性的CLO人工抗原,并获得敏感性高,特异性强的CLO鼠源多抗血清。     

Autoinducer-2 associated inhibition by Lactobacillus sakei NR28 reduces virulence of enterohaemorrhagic Escherichia coli O157:H7

Bacteria use quorum sensing (QS) to regulate the expression of certain target genes for social behaviour. A LuxS/AI-2 signalling system serves to control the virulence of some pathogenic bacteria by mechanisms such as motility, biofilm formation and attachment, and is typical of the enterohaemorrhagic Escherichia coli O157:H7 (EHEC) associated with infections of the human intestine. The LuxS/AI-2 signalling system presents an interesting potential as antimicrobial target for appropriate AI-2 inhibitors, and thus widens the scope for treatment or prevention of infections by pathogens such as EHEC. Probiotic lactic acid bacteria (LAB) are primary candidates for this approach because of their general acceptability, safety and adaptation to the intestinal and/or food ecosystem. In this paper, we report on Lactobacillus sakei NR28 as a new candidate strain for AI-2 related quorum quenching. It is considered to be a putative probiotic strain and was originally isolated from kimchi, a traditional Korean fermented food known for its special health features. This study has shown that AI-2 activity and the associated virulence factors of the EHEC ‘wild-type’ strain E. coli ATCC 43894, were significantly reduced by L. sakei NR28, while, at the same time, the cell viability of the EHEC strain was not affected. In addition, the purified AI-2 molecule, a luxS-deficient mutant of EHEC strain ATCC 43894, and an AI-2 independent EHEC mimicking strain of Citrobacter rodentium were used to determine the relationship between the virulence reducing effect of L. sakei NR28 and its AI-2 inhibiting ability. Our results showed that L. sakei NR28 has a reducing effect on the pathogenicity of the ‘wild-type’ EHEC strain ATCC 43894 by AI-2 signalling inhibition.     

An interactive virtual prototyping platform considering environment effect described by fluid dynamics

Virtual prototyping (VP) technology has been regarded as a cost-effective way of envisaging real circumstances that enhance effective communication of designs and ideas, without manufacturing physical samples. Different from recent interactive VPs that are only based on multi-body systems, our VP platform is based on a multi-body coupled with fluid system, that is, the performance and functions of a VP will not be independent of environment factors or disturbances but interact with each other and constitute a whole system. Using this platform designers can simulate a robot through vacuum, air, water environments, etc., so it can provide a better support to the generality and quality of a VP. As for interactive manipulation, designers can modify the constraints between bodies, apply force/torque to interested bodies and change the parameters of forces/torques. Corresponding to user interaction, the platform automatically updates the dynamic behavior of the VP under current condition in the simulation loop. Furthermore, we implemented a virtual MiniBaja vehicle to verify the interactivity and effectiveness of this platform.     

Development of a rapid magnetic bead-based immunoassay for sensitive detection of zearalenone

Here we demonstrate a novel magnetic bead-based enzyme-linked immunosorbent assay (MB-ELISA) for zearalenone (ZEN) detection. Firstly, an anti-ZEN monoclonal antibody (mAb) was prepared by hybridoma technique, and immobilized on carboxyl modified MBs to obtain mAb-MBs. In addition, the biotinylated ZEN-BSA was labelled by streptavidin-HRP for use as competitor. Based on the mAb-MBs and streptavidin-HRP labelled ZEN-BSA, a MB-ELISA which contains only one 20 min antigen-antibody reaction step and takes no more than 45 min for dozens of samples analysis was developed. The half maximal inhibitory concentration (IC₅₀) and limit of detection (LOD) of the MB-ELISA are 1.78 ng/mL and 0.13 ng/mL, respectively. And the MB-ELISA working range for corn samples analysis is from 5.0 μg/kg to 255.2 μg/kg. The recoveries for ZEN spiked corn samples ranged from 82.3 to 110.5% with coefficient of variation (CV) under 8.9%. For natural corn samples analysis, the results of MB-ELISA showed good agreement with the results of conventional direct competitive ELISA (R² = 0.9742).     

Development of a lateral flow colloidal gold immunoassay strip for the simultaneous detection of Shigella boydii and Escherichia coli O157:H7 in bread,milk and jelly samples

A colloidal gold immunochromatographic strip (ICS) was proposed with double monoclonal antibodies (McAbs) for rapid detections of multiple foodborne pathogens, and we successfully developed a model strip for simultaneous detection of Shigella boydii (S. boydii) and Escherichia coli O157:H7 (E. coli O157:H7) in this study. The sensitivity of the strip test was determined to be 10⁶ CFU/mL for both S. boydii and E. coli O157:H7. There was no cross-reaction with other related bacteria. Parallel analysis of pathogen detection from bread, milk and jelly showed consistent results between the strip test and enzyme-linked immunosorbent assay (ELISA). The detection limit was substantially improved to 4 CFU/mL of the original bacterial content after pre-incubation of the bread, milk and jelly samples in broth for 10, 10 and 8 h respectively. This ICS was able to finish test within 5–10 min and has advantages in high throughput and easy operation without requiring sophisticated equipment and specialized skills. Overall, to our knowledge, this is the first report of semi-quantitative ICS for simultaneously detecting two pathogens. This protocol might provide insight into the development of ICS technology for simultaneously examining multiple food-borne pathogens from foods.     

A comparison of the ability of several small and large deformation rheological measurements of wheat dough to predict baking behaviour

The rheological characteristics of twenty wheat flour samples obtained from four organic flour blends and a non-organic control were compared in relation to their ability to predict subsequent loaf volume in the baked bread. The flour samples considered had protein contents that varied between 11–14 g/100 g. Four different rheological methods were employed. Oscillatory stress rheometry on the protein gel extracted from the wheat flour, oscillatory stress rheometry and creep measurement on undeveloped dough samples and biaxial extensional measurements on simple flour–water doughs. None of the fundamental rheological parameters correlated with loaf volume. There was a correlation between the storage modulus of the gel protein and storage modulus for the undeveloped dough (r = 0.85). There was a weak negative correlation between protein content and biaxial extensional viscosity (r = −0.62). Stepwise multiple regression related loaf volume to dough stability time (measured on the Farinograph) and tan (phase angle) for the undeveloped dough samples (overall model r² = 0.54). The results indicate that the four rheological tests considered could not be used as predictors of subsequent loaf volume when the bread is baked.