腰果过敏原Ana o 2结构及抗原表位预测

腰果是引起人们过敏的主要食物之一。作者采用生物信息学方法,通过Pubmed网络服务器、生物信息分析软件SOPMA、swiss-model网络服务器、DNAStar生物分析软件等对腰果主要过敏原Ana o 2的结构和抗原表位进行预测,分析Ana o 2蛋白的抗原表位可能是108-111,181-186,217-218,234-238,244-255,283-287。这为腰果过敏原的进一步研究提供理论参考,并对开发低过敏腰果制品提供帮助。     

腰果过敏原Ana o 3蛋白的分离纯化及热稳定性研究

Ana o 3蛋白是腰果主要的过敏原之一。以生腰果为原料,通过粉碎脱脂、低盐提取粗蛋白、冷冻干燥、阴离子交换层析及超滤浓缩等过程分离得到目的蛋白,利用小分子蛋白电泳、液相色谱-串联质谱和免疫印迹技术进行鉴定;此外,采用紫外光谱及圆二色光谱分析腰果过敏原Ana o 3蛋白在160℃持续加热10、15、20、25、30min的结构变化,以评估分离纯化后腰果过敏原Ana o 3蛋白的稳定性。结果表明,成功建立了一种快速高效纯化腰果过敏原Ana o 3蛋白的方法,该方法获得的蛋白纯度高于95%。通过圆二色光谱发现腰果过敏原Ana o 3蛋白在160℃加热过程中α-螺旋构象逐步转变为β-折叠构象,β-转角含量变化较小,无规则卷曲含量稍有增加,表明该蛋白二级结构较为稳定;经紫外光谱发现加热后腰果过敏原Ana o 3蛋白的紫外特征吸收峰的吸光度升高,表明加热会使腰果过敏原Ana o 3蛋白变性,结构展开,更多的色氨酸和酪氨酸残基暴露,使得空间结构变得松散;经蛋白电泳和免疫印迹分析发现,热处理后腰果过敏原Ana o 3蛋白会发生降解,表位被破坏。希望研究可为高纯度腰果过敏原Ana o 3蛋白的纯化提供方案,为腰果过敏的研究提供基础,为腰果过敏原在热加工过程中的稳定性研究提供理论依据。     

坚果类过敏原的分离及免疫印迹分析

本文采用传统的丙酮、乙醚溶剂去脂方法,选用不同品种和不同种类的坚果食品对其进行过敏蛋白的初步分离,应用BCA蛋白试剂盒测定各蛋白浓度,通过SDS-PAGE电泳分离坚果过敏蛋白各组份,采用免疫印迹(Western-blotting)方法鉴定坚果蛋白的过敏性。结果表明,各坚果蛋白提取浓度为白芝麻:14 mg/mL,黑芝麻:4 mg/mL,核桃:8 mg/mL,腰果:28 mg/mL,开心果:21 mg/mL。SDS-PAGE电泳显示15 ku是白芝麻的主要蛋白,34 ku是黑芝麻的主要蛋白,19和37 ku是腰果的主要蛋白,13 ku是核桃的主要蛋白,13和21 ku是开心果的主要蛋白。Western-Blotting显示对过敏患者的阳性混合血清均有过敏反应,坚果过敏具有同源性,白芝麻与黑芝麻的主要过敏原分子量均在22 ku,腰果的主要过敏原分子量在20 ku,核桃的主要过敏原分子量在54 ku,开心果的主要过敏原分子量在23 ku。     

国外食品中麸质过敏原法规标准现状及其对我国的启示

麸质作为一类主要的过敏原成分,过敏被视为一种严重的公共营养问题,已成为国际社会关注的重点。国际食品法典委员会以及美国、欧盟、日本、阿根廷等国家（地区）先后出台了相关法规标准,而我国在食品过敏原成分标识管理方面还存在空白。本文通过对国外食品中麸质过敏原相关标准的研究,提出制定以麸质过敏原成分为代表的食品过敏原成分标识标准等建议,为我国相关政策和标准的制定提供参考。     

乳品安全中的牛乳过敏

牛乳过敏是婴幼儿中一种常见的食物过敏,严重危害婴幼儿健康。对牛乳过敏的机理、牛乳中的过敏原成分、牛乳过敏原的检测、加工对牛乳过敏原的影响作了详细的介绍。     

花生过敏原及其检测方法研究进展

花生过敏可导致某些人群严重的食品安全问题。过敏患者只能通过避免食用含有花生过敏原成分的食物来避免过敏。但是,食品在生产加工、储存、运输、销售过程中有可能被过敏原污染。因此,确定各类加工食品中是否含有花生过敏原成分,对于预防食用者发生花生过敏反应具有重要意义。花生中已确定的过敏原蛋白有13种(Ara h 1~Ara h 13)。本文综述了花生中过敏原蛋白的结构信息,当前流行的提取方法,以及各种定性定量的检测方法,总结了各种方法的优缺点。同时对建立一种具有特异性强、灵敏度高、定量准确的花生致敏蛋白检测方法的发展趋势进行了展望。     

基于高通量-生物信息技术的食物过敏组学研究进展

食物过敏是严重的全球性健康安全问题,对过敏原的研究是预防和治疗过敏的基础。随着大数据时代的到来,利用高通量技术研究过敏原成为可能,过敏组学应运而生。过敏组学是研究过敏原的集合——过敏组的学科,具有通量高、覆盖面广和快速灵敏等特点,能够为个性化的过敏原回避预防和免疫治疗提供依据。本文介绍了过敏组学的一般概念,总结了过敏组学的研究方法,评价了不同方法的优势和局限性,并对其发展前景进行了展望,以期为过敏组学在食品安全等领域的应用和发展提供参考。     

桃过敏原的种类、制备、鉴定及检测技术研究进展

作为日常食用的植物源食品,水果可为人体提供糖类、维生素、矿物质等多种营养物质,从而调节机体的多项生理功能。然而,水果中的致敏成分可诱发过敏反应,由此引发的食品安全问题也越来越引起关注。桃是一种最常见的过敏水果,可引起轻微过敏症状和严重过敏反应甚至过敏性休克。文章综述桃过敏原的种类、亚类及其生物特性,阐述不同亚类桃过敏原在品种或地区的差异性,总结桃过敏原的分离制备方法和分子鉴定技术,并从过敏原基因检测、免疫检测技术和仪器检测技术3个方面对桃过敏原检测技术进行概括,以期为桃过敏原的致敏机制、消减技术和食品加工的安全控制提供研究基础。     

腰果主要过敏原Ana o 3的重组表达与鉴定

目的克隆获得腰果主要过敏原Ana o 3基因,并利用pCold-SUMO原核表达载体重组表达Ana o 3并鉴定免疫活性。方法提取腰果总RNA,逆转录至c DNA,设计特异性引物,通过巢式PCR技术克隆腰果Ana o 3基因,将其插入pCold-SUMO vector,鉴定并测序;将测序正确的阳性质粒转化大肠埃希菌BL21(DE3),低温15℃诱导表达。摸索诱导表达条件,经镍柱纯化,并通过Western blot鉴定免疫活性。结果测序结果表明,克隆腰果Ana o 3基因片段全长为417 bp,与GenBank上Ana o 3基因CDS序列基本一致;十二烷基硫酸钠聚丙烯酰胺凝胶电泳结果表明,目的蛋白分子量为27 kD左右,大小与理论值相符;Western blot结果表明,与腰果过敏阳性血清具有良好的反应性。结论从腰果中成功克隆了Ana o 3基因,并于原核系统表达了Ana o 3蛋白,证实了此蛋白与腰果过敏血清具有良好的反应性。     

鸡蛋过敏原表位研究进展

鸡蛋过敏是一种常见的食物过敏反应,是人体对鸡蛋中蛋白质成分产生的一种变态反应。食物过敏反应的物质基础是抗原表位与抗体对位,解决食物过敏反应问题的关键一点即需要深入研究出过敏原的表位。本文介绍了鸡蛋中6种主要过敏原,简述了过敏原表位的定位方法,并详细综述了卵白蛋白、卵类粘蛋白、卵转铁蛋白和溶菌酶的过敏原表位研究进展。本文可为进一步鸡蛋过敏研究提供理论指导,也可为表位成分的定量检测以及无毒副作用鸡蛋过敏原疫苗的开发等方面提供一些参考。     

Pistachio nut allergy: An updated overview

Pistachio nut (Pistacia vera) is highly appreciated for its organoleptic characteristics and potential health benefits. However, this tree nut is also responsible for triggering moderate to severe IgE-mediated reactions in allergic individuals. Currently, pistachio nut allergy has gained some special attention, mainly due to its intrinsic relation with cashew nut allergy. Like for other nuts, the prevalence of pistachio nut allergy seems to be increasing at a global scale. Until now, there are five allergenic proteins officially listed for pistachio nut (Pis v 1, Pis v 2, Pis v 3, Pis v 4 and Pis v 5). Relevant data on their biochemical classification has become available, enabling establishing a correlation with the respective clinical symptoms. The establishment of an effective allergen risk assessment is a key issue for the food industry, policy makers and regulatory agencies. Thus, the availability of fast, specific and sensitive methods to detect trace amounts of allergens in processed foods is crucial. In the specific case of pistachio nut, there are some protein- and DNA-based methods for its detection/quantification in foods, which can aid to verify label information. Accordingly, all relevant research advances on this topic were summarised, updated and critically discussed in this review.     

Processing effects on tree nut allergens: A review

“Tree nut” is a broad term for classification of nuts that include cashews, almonds, hazelnuts, etc. Reports of mild to adverse immune reactions following the consumption of these nuts has been on a rise in recent years. Currently, about 1.2–2% of the world's population suffer from sensitivity to tree nuts. The only solution is complete abstinence from the allergy causing tree nut which is not feasible in most cases due to issues like cross contamination or their presence in the form of hidden ingredients in processed foods. Various studies have shown that food processing can effectively vary the secondary structures of the allergenic protein which in turn influences their functional properties. But, the impact of these processing methods on tree nuts allergens is mixed. This review gives an update on the recent findings on how conventional and novel processing methods influence the tree nut allergens.     

坚果中主要过敏原种类、检测及脱敏技术研究进展

近年来由于摄入坚果而导致的过敏反应屡见报道,已成为影响和威胁人体健康的一类重要的食品安全问题。本文对坚果中常见的过敏原的性质及危害进行了介绍,列举了目前国内外用于坚果过敏原检测的主要技术、特点及其应用,对比分析了不同处理方式对坚果中过敏原脱敏效果以及优缺点,指出目前坚果中过敏原检测及脱敏技术的不足和今后发展展望,旨在为坚果的加工和消费提供理论基础,助推坚果产业发展。     

Fracture Resistance of Cashew Nuts as Influenced by Pre-Shelling Treatment

The fracture resistance of raw and pre-treated cashew nuts during uni-axial compressive loading was investigated. Cashew nut samples were subjected to two pre-shelling treatments, namely: steam boiling and roasting in hot cashew nut shell liquid. Two loading rates of 2.5 and 50 mm/min and two loading orientations (longitudinal and transverse) were considered for fracture resistance of pre-treated cashew nuts using a 50 kN capacity Instron testing machine. The data obtained were subjected to analysis of variance. The average values at 2.5 mm/min were 342 and 318 N for raw nuts, 321 and 242 N for roasted nuts, and 341 and 309 N for steam boiled nuts during longitudinal and transverse loading, respectively; whereas corresponding values at 50 mm/min were 784 and 763 N for raw nuts, 517 and 464 N for roasted nuts, and 436 and 398 N for steam boiled nuts, respectively. In each of the pre-treatment methods and loading rates, more force was required to crack cashew nuts during longitudinal loading than transverse loading; and for each loading rate, pre-treated nuts generally required less force than raw nuts.     

Antioxidative potential of cashew phenolics in food and biological model systems as affected by roasting

The effect of different roasting conditions on antioxidant capacity of phenolics of cashew nuts and their testa was evaluated using several food and biological model systems. Total phenolic content (TPC) of cashew extracts was determined and accelerated oxidative stability of stripped corn oil in the presence of cashew extracts evaluated. In addition, the antioxidant activity of the extracts was assessed in a β-carotene-linoleate and a cooked comminuted pork model system. Inhibition of oxidation of human low density lipoprotein (LDL) cholesterol and stand breaking of supercoiled deoxyribonucleic acid (DNA) was also investigated. The TPC ranged from 5 to 791 mg gallic acid equivalents/g crude extract. In general, whole cashew nuts and testa extracts demonstrated stronger antioxidant activity than that of the cashew kernel. The inhibition percentage of LDL cholesterol oxidation, as evaluated by conjugated dines formation, of cashew kernels was higher than that of testa and was 69% at the end of 24 h incubation. Extracts of roasted cashew nut showed considerable antioxidative efficiency in model systems employed in this study, however, the effect was not significantly (P ? 0.05) different from that of their raw counterparts, except for the accelerated oxidative stability assay. The results suggest that whole cashew nut and testa extracts could be used as a potential source of natural antioxidants in certain food applications and for disease risk reduction.     

Survey of peanut levels in selected Irish food products bearing peanut allergen advisory labels

Peanut allergy affects up to 2% of consumers and is responsible for the majority of fatalities caused by food-induced anaphylaxis. Peanut-containing products must be clearly labelled. Manufacturers are not legally required to label peanut if its inclusion resulted from unintentional cross contact with foods manufactured in the same facility. However, the use of allergen advisory statements alerting consumers of the potential presence of peanut allergen has increased in recent years. In previous studies, the vast majority of foods with precautionary allergen statements did not contain detectable levels of peanut, but no data are available on Irish food products. Thirty-eight food products bearing peanut/nut allergen-related statements were purchased from multiple locations in the Republic of Ireland and analysed for the presence of peanut. Peanut was detected in at least one lot in 5.3% (2 of 38) of the products tested. The doses of peanut detected ranged from 0.14 mg to 0.52 mg per suggested serving size (0.035–0.13 mg peanut protein). No detectable levels of peanut were found in the products that indicated peanut/nuts as a minor ingredient. Quantitative risk assessment, based on the known distribution of individual threshold doses for peanut, indicates that only a very small percentage of the peanut-allergic population would be likely to experience an allergic reaction to those products while the majority of products with advisory labels appear safe for the peanut-allergic population. Food manufacturers should be encouraged to analyse products manufactured in shared facilities and even on shared equipment with peanuts for peanut residues to determine whether sufficient risk exists to warrant the use of advisory labelling. Although it appears that the majority of food products bearing advisory nut statements are in fact free of peanut contamination, advice to peanut allergy sufferers to avoid said foods should continue in Ireland and therefore in the wider European Union.     

Functional properties of raw and heat processed cashew nut (Anacardium occidentale, L.) kernel protein isolates

The functional properties viz. solubility, water and oil absorption, emulsifying and foaming capacities of the protein isolates prepared from raw and heat processed cashew nut kernels were evaluated. Protein solubility vs. pH profile showed the isoelectric point at pH 5 for both isolates. The isolate prepared from raw cashew nuts showed superior solubility at and above isoelectric point pH. The water and oil absorption capacities of the proteins were slightly improved by heat treatment of cashew nut kernels. The emulsifying capacity of the isolates showed solubility dependent behavior and was better for raw cashew nut protein isolate at pH 5 and above. However, heat treated cashew nut protein isolate presented better foaming capacity at pH 7 and 8 but both isolates showed extremely low foam stability as compared to that of egg albumin.     

Sandwich enzyme-linked immunosorbent assay (ELISA) for detection of cashew nut in foods

The presence of undeclared cashew can pose a health risk to cashew-allergic consumers. The food industry has the responsibility to declare the presence of cashews on packaged foods even when trace residues are or might be present. The objective of this study was to develop a rapid, sensitive, and specific enzyme-linked immunosorbent assay (ELISA) for the detection of cashew residues. Raw and roasted cashews were defatted and used separately to immunize sheep, goats, and rabbits. The cashew ELISA was developed using sheep and rabbit polyclonal anti-roasted cashew sera as capture and detector reagents, respectively, with visualization through an alkaline phosphatase-mediated substrate reaction. The cashew ELISA was shown to have a limit of quantification of 1 ppm (1 μg cashew/g). The ELISA was highly specific except that substantial cross-reactivity was noted with pistachio and a lesser degree of cross-reactivity was noted with hazelnut. The performance of the ELISA was assessed by manufacturing cookies, ice cream, and milk chocolate with added known amounts (0 to 1000 ppm) of cashew. The mean percent recoveries for ice cream, cookies, and milk chocolate were 118%± 2.9%, 84.3%± 4.0%, and 104%± 3.0%, respectively. In a limited retail survey, 4/5 retail samples with cashew declared on ingredient labels tested positive for cashew compared to 5/36 samples of foods with precautionary labels indicating the possible presence of one or more tree nuts and 0/18 samples without cashew declared on the label in any manner. The cashew ELISA can be used to detect undeclared cashew residue in foods and as a potential tool for the food industry to assess the effectiveness of allergen control strategies and to guarantee compliance with food labeling regulatory requirements.     

Effect of roasting duration on the solubility,structure, and IgE-binding capacity of cashew nut proteins

Cashew nuts can induce severe allergic reactions in some allergic individuals. In this work, the solubility, structure and IgE-binding capacity of cashew proteins roasted for different durations were compared. The solubility of cashew nut proteins decreased after roasting. Ana o 3 and Ana o 2 was more thermally stable than Ana o 1. The analysis of the structure of cashew extracts by Fourier transform infrared spectroscopy and environmental scanning electron microscopy demonstrated that roasting reduced the contents of β-sheet and β-turn and led to the unfolding and aggregation of cashew protein. The IgE-binding capacity of cashew protein extracts seemed to decrease with the extension of roasting time.     

Hazelnut Allergens: Molecular Characterization,Detection, and Clinical Relevance

In last few years, special attention has been given to food-induced allergies, in which hazelnut allergy is highlighted. Hazelnut is one of the most commonly consumed tree nuts, being largely used by the food industry in a variety of processed foods. It has been regarded as a food with potential health benefits, but also as a source of allergens capable of inducing mild to severe allergic reactions in sensitized individuals. Considering the great number of reports addressing hazelnut allergens, with an estimated increasing trend, this review intends to assemble all the relevant information available so far on the following main issues: prevalence of tree nut allergy, clinical threshold levels, molecular characterization of hazelnut allergens (Cor a 1, Cor a 2, Cor a 8, Cor a 9, Cor a 10, Cor a 11, Cor a 12, Cor a 14, and Cor a TLP) and their clinical relevance, and methodologies for detection of hazelnut allergens in foods. A comprehensive overview of the current data about the molecular characterization of hazelnut allergens is presented, relating to biochemical classification and biological function with clinical importance. Recent advances in hazelnut allergen detection methodologies are summarized and compared, including all the novel protein-based and DNA-based approaches.