芝麻过敏原PCR检测方法

芝麻是重要的食品过敏原之一,微小剂量即可引起严重的过敏反应。针对芝麻过敏蛋白-2S白蛋白的基因序列设计PCR扩增引物,建立并优化芝麻过敏原检测的普通聚合酶链式反应(PCR)和实时荧光定量聚合酶链式反应(Real-time PCR)方法。结果表明,两种方法的最低检测限分别为0.1,0.01ng DNA,该方法特异性良好,成本较低,具有一定的应用价值。     

恒温实时荧光法快速检测简单异尖线虫方法的建立

为了快速鉴定简单异尖线虫,本研究建立了一套检测简单异尖线虫DNA的恒温实时荧光环介导等温扩增（loop-mediated isothermal amplification,LAMP）方法,根据LAMP方法原理,针对简单异尖线虫ITS2区域设计引物特异性识别靶标基因。进行了特异性、灵敏度、重复性和实际样品的测试,并与传统的PCR方法进行比较。结果表明,该方法能够特异性扩增简单异尖线虫DNA,对含有简单异尖线虫ITS2目的基因片段的质粒DNA检测限为1 fg/μL,灵敏度比传统的PCR方法高100倍,重复性良好,对实际样品进行检测,与传统的PCR测序方法结果相符。本研究建立的恒温实时荧光快速检测方法适用于特异性检测简单异尖线虫。      

进境水产品中典型异尖线虫恒温实时荧光检测法的建立与应用

本研究建立了一套检测进境水产品中典型异尖线虫DNA的恒温实时荧光环介导等温扩增(loop-mediated isothermal amplification,LAMP)方法,根据LAMP方法原理,针对典型异尖线虫ITS2区域设计三套引物,特异性识别靶标基因。对比验证了典型异尖线虫、简单异尖线虫、短棘异尖线虫、抹香鲸异尖线虫、Anisakis nascettii、宫脂线虫、对盲囊线虫和颚口线虫的引物特异性;研究了模板浓度1 ng/μL至10 ag/μL的LAMP反应灵敏度,比传统的PCR方法高100倍;并在最低检测限1 fg/μL的质粒模板进行15次重复试验;对来自不同热带国家和地区的进境的41个实际样品进行测试,与传统PCR方法进行比较,假阳性率为0。恒温实时荧光快速检测方法适用于特异性检测典型异尖线虫。     

荧光定量PCR技术在食品快速检测中的应用

荧光定量聚合酶链式反应（real-time quantitative polymerase chain reaction,qPCR）是一种将聚合酶链式反应（polymerase chain reaction,PCR）扩增与实时检测相结合的技术,也是近年来食品快速检测技术的研究热点之一。与传统PCR技术相比,它具有耗时短、操作简单、灵敏度高、特异性强等优势。本文简要概述了荧光定量PCR技术的基本原理、发展历程、分类及特点,综述了荧光定量PCR技术在食源性致病菌、掺杂掺假、转基因食品、过敏原、食源性寄生虫、可食用昆虫等食品检测中的应用,并对荧光定量PCR技术及其在食品快速检测中应用的前景进行了展望。     

不同食品加工方式对提取鮟鱇鱼肉DNA的影响

目的研究不同食品加工方式对提取鮟鮟鱼肉DNA的影响。方法以实时荧光PCR方法检测鮟鮟鱼成分标准为例,采取水煮、微波、油炸3种处理方式,选用试剂盒提取DNA,利用核酸蛋白测定仪测定其在260 nm、280 nm处的吸光度,通过A260来计算核酸浓度,A260/A280来评估核酸的纯度。以提取的DNA为模板,进行实时荧光PCR扩增。通过Ct值判断不同加工方式对实时荧光PCR结果的影响。结果水煮、微波、油炸3种加工方式中,油炸对DNA的影响最明显,当在高温下油炸时间过久会导致鱼肉焦糖化反应及蛋白质变性严重,变成具有一定孔隙的焦状物,此时鱼肉在提取DNA的过程中难以消化,造成DNA提取量少,最终导致实时荧光PCR结果假阴性。而水煮、微波两种加工方式即使处理时间过久也没有对实时荧光PCR结果产生明显影响。结论在鱼制品使用实时荧光PCR方法检测时,应充分考虑加工方式对鱼制品DNA的影响。     

食品中荧光假单胞菌的危害及其快速检测方法研究进展

荧光假单胞菌(Pseudomonas Fluorescens)隶属于假单胞菌属,是食品中常见的一种嗜冷致病微生物。它能够产生极其耐热的蛋白酶和脂肪酶,这些酶在高温处理后仍有残留,并在食品储藏过程中继续分解其中的脂肪和蛋白质,导致产品的风味和质地发生变化。因此,研发出一种既快速又实用的荧光假单胞菌检测方法成为食品行业关注的焦点。本文对食品中荧光假单胞菌的危害特点及国内外的一些快速检测方法,如聚合酶链式反应(PCR)、荧光定量PCR、荧光原位杂交、流式细胞术等方法进行了综述,比较各方法的优缺点并展望了荧光假单胞菌快速检测方法的发展趋势。      

肉制品异源基因检测技术研究进展

近年来,食品掺假逐渐成为消费者关注的重要食品安全问题之一。由于利益的驱使,在肉制品行业异 源肉质掺假现象尤其严重。目前,用于肉制品异源基因检测的技术包括普通聚合酶链式反应（polymerase chain reaction,PCR）技术、DNA指纹技术、实时荧光定量PCR技术、微滴式数字PCR技术、DNA条形码技术等。本文 综述了肉制品中异源基因检测技术的研究进展,并对每种方法的优缺点和发展趋势予以讨论。     

定量检测食品中榛果过敏原成分

定量检测食品中过敏原榛果过敏蛋白,构建目的基因的标准品及标准曲线。以榛果的DNA为模板,针对油体蛋白基因设计引物进行PCR扩增,构建质粒,经鉴定测序,用荧光定量PCR制作标准曲线。成功克隆油体蛋白目的基因片段,并以此为标准制作出荧光定量PCR标准曲线,线性关系良好,灵敏度高,检测限低于10个拷贝,特异性强,准确可靠。成功建立荧光PCR方法定量检测食品中过敏原榛果成分,构建油体蛋白基因的标准品及标准曲线。     

北极苹果结构特异性实时荧光聚合酶链式反应检测方法建立

目的为实现转基因北极苹果(Arctic~(TM) apple)目的标识管理,建立特异性实时荧光聚合酶链式反应(polymerase chain reaction,PCR)检测方法。方法针对转基因北极苹果特异性序列设计引物和TaqMan探针,建立转基因北极苹果实时荧光PCR检测方法,并对该方法的特异性、灵敏度和重复性进行检测。结果建立的转基因北极苹果实时荧光PCR特异性强,定量检测限为20拷贝,扩增效率为96%,检测重复性良好。结论建立的特异性实时荧光PCR法可应用于转基因北极苹果的鉴定。     

热处理羊乳酪蛋白结构与抗原性的变化规律

热加工处理羊乳 α-酪蛋白(α-casein,α-CN)和 β-酪蛋白(β-casein,β-CN),通过圆二色谱、荧光光谱等方法探索不同热加工条件下羊乳的蛋白结构变化与抗原性的关系.结果表明:随着对蛋白热处理温度的升高,会破坏羊α-CN和β-CN的天然结构,使得分子内部发生交联或聚集,导致分子量发生改变,分子内游离羰...     

Direct competitive enzyme‐linked immunosorbent assay (ELISA) for rapid screening of anisakid larvae in seafood

BACKGROUND: Anisakid larvae are one of the most important pathogenic parasites in marine products; however, simple and rapid analytical techniques for them are still very limited. In this research, based on specific rabbit polyclonal antibodies which were raised against crude extracts of Anisakis larvae, purified by protein A affinity chromatography and labeled with horseradish peroxidase, a direct competitive enzyme‐linked immunosorbent assay (ELISA) was developed and validated for detection of anisakid larvae in seafood. RESULTS: The established method exhibited a broad selectivity to Anisakis larvae and Pseudoterranova larvae, and the lowest detection limit to them was estimated to be about 5 parasites kg^?1 in food matrix. Using Pseudopleuronectes yokohamae, Scomberomorus niphonius and Ommastrephes bartrami as samples and within spiking concentrations from 20 to 100 larvae kg^?1, the determination recovery for Anisakis larvae and Pseudoterranova larvae ranged from 77.8% to 107.0%, with relative standard deviations all less than 20%. CONCLUSION: The results allowed us to suggest the established direct competitive ELISA as an effective analytical tool for fast screening of anisakid larvae in sea foods. Copyright © 2010 Society of Chemical Industry     

Extracellular Protease from Pseudomonas marinoglutinosa: Some Properties and Its Action on Fish Actomyosin

A bacterium isolated from Indian mackerel (Rastrelliger kanagurta) and identified as Pseudomonas marinoglutinosa, was found to produce appreciable amounts of extracellular protease when grown in nutrient medium. This enzyme which degraded several proteins, was found to be most active against mackerel myofibrillar proteins. The optimum temperature and pH range for enzyme activity were 50°C and 7–8 respectively. Treatment of mackerel actomyosin with the protease at 0–2°C for 4 days resulted in degradation of the protein as assessed by release of tyrosine, loss in Mg⁺⁺-dependent ATPase activity and changes in SDS-polyacrylamide gel electrophoretic patterns.     

Optimising the frying temperature of gluten balls using response surface methodology

The continuous frying process of gluten balls involved three consecutive deep frying pans. The effects of the temperatures of the first and the second deep frying pans on the quality indices of the obtained fried gluten balls, including expansion volume, expansion ratio, measured value of textural property, Hunter colour b value, and sensory evaluation score, were investigated using response surface methodology while fixing the temperature of the third deep frying pan at 195±3°C. Based on the obtained sensory evaluation scores, the peak force and brittleness breakdown of textural properties, as well as Hunter colour b value of the fried gluten balls, it was found that the optimum temperature ranges for the first and the second deep frying pans were 130–143°C and 155–161°C, respectively. © 1998 SCI.     

Effects of deep‐fat frying temperature on antioxidant properties of whole wheat doughnuts

The total phenolic (TP) content, phenolic acid composition and in vitro antioxidant capacity of whole wheat doughnuts fried at 120–180 °C were determined to identify the effects of frying temperature. Significant differences (P < 0.05) in TP content were observed between doughnuts fried at different temperatures. The TP content of doughnuts decreased significantly when doughnuts were deep‐fat fried. The TP content of doughnuts increased with elevation with frying temperatures. These increases in TP content of doughnuts were also detected in the determination of individual phenolic compounds using HPLC. DPPH radical and iron‐chelating capacity of deep‐fat fried doughnuts exhibited increases with elevation of frying temperature from 120 to 180 °C. Deep‐fat frying at 120 °C lowered lipid peroxidation inhibition capacity of doughnuts prepared from both refined flour and whole‐grain meals and increased consistently with increased frying temperature from 120 to 180 °C. Moderate deep‐fat frying temperature would increase the content and activity of antioxidants of doughnuts.     

A chromametric method for the rapid assessment of deep frying oil quality

A rapid chromametric method was developed for the assessment of deep frying oil quality based on the strong correlation between colour index and total polar compounds in deep frying oil. Colour indices of frying oil samples, measured by chromameter, decreased significantly during frying and were strongly correlated with frying time (r ≥ 0.95, p < 0.001). Colour indices of a set of oil samples taken from 0 to 80 h of deep frying were also significantly correlated with total polar compounds of the same samples determined using the official method of the American Oil Chemists' Society (r = 0.96, p < 0.001). The equation for conversion of the colour index (x) to the content of total polar compounds (y) in an oil sample is y = 0.0174x² ? 2.9506x + 124.34. In addition, colour indices of 10 different types of frying oils were strongly correlated with the corresponding contents of total polar compounds in the oils with samples taken from 0 to 80 h of deep frying in duplicate (r = 0.95, p < 0.001, n = 220). The results of colour index analyses agreed well with the results of chemical and sensory analyses of the frying oils tested. This chromametric method is rapid, convenient and reliable. Copyright © 2003 Society of Chemical Industry     

Effects of different cooking methods on the formation of food mutagens in meat

Hamburgers and chicken fillets were cooked in convection ovens, deep‐fried or contact fried and analysed for mutagenic activity using the Ames test. For the three different convection ovens, the cooking parameters studied included the presence of steam, air velocity, air temperature and holding time. For deep‐frying and contact frying, the cooking parameters included cooking temperature and cooking time. In cooked hamburgers, mutagenic activity was only detected in those that had been deep‐fried. In chicken fillets, mutagenic activity was detected in samples prepared with all cooking methods, being highest in the deep‐fried samples. Factorial analysis indicated that heat transfer was the most important factor affecting mutagenic activity. High temperature and high air velocity in the convection ovens enhanced mutagenic activity. The presence of steam reduced the mutagenic activity, except when high temperature was used in combination with high air velocity. In chicken fillets, high mutagenic activity correlated to high weight loss during cooking. Pan‐fried chicken fillets were analysed using high performance liquid chromatography (HPLC) and the mutagenic/carcinogenic heterocyclic amines 2‐amino‐3,8‐dimethylimidazo[4,5‐f ]‐quinoxaline (MeIQx), 2‐amino‐1‐methyl‐6‐phenylimidazo‐[4,5‐b]‐pyridine (PhIP) and the co‐mutagenic heterocyclic amine Norharman (9H‐pyrido[3,4‐b]‐indole) were identified. The HPLC fractions were tested for mutagenic activity and, apart from the mutagenic fractions corresponding to MeIQx and PhIP, several mutagenic fractions were detected that did not correspond to known heterocyclic amines.     

Application of protein-based edible coatings for fat uptake reduction in deep-fat fried foods with an emphasis on muscle food proteins

BackgroundDeep-fat frying is a common cooking method where fat or oil is used as the heat transfer medium, in direct contact with the food at a temperature above the boiling point of water. During the deep fat frying method, oil not only serves as a heating medium but also absorbs into food, increasing the total fat content. As a result, consumption of deep-fat fried foods has been associated with coronary heart diseases, obesity and type 2 diabetes. Selection of an appropriate food coating before frying may act as a barrier to moisture loss, which is important commercially, and also reduce fat uptake during frying.Scope and approachThis paper succinctly reviews different protein sources for edible coatings and compare them with muscle food proteins which were used in deep-fat fried foods.Key findings and conclusionsProtein-based coatings have been explored as potential coating materials in fat-uptake reduction. Comparatively, proteins are able to form films with better mechanical and barrier properties than polysaccharides. Application of muscle food proteins (myofibrillar proteins) as coatings, which are rich in these proteins, is novel and could be product-friendly for deep-fried muscle foods.     

Change of fatty acid esters of MCPD and glycidol during restaurant deep frying of fish nuggets and their correlations with total polar compounds

This study examined the fatty acid esters of 2-monochloropropane-1,2-diol (2-MCPD), 3-monochloropropane-1,2-diol (3-MCPD) and glycidyl esters (GEs) in frying oils during fish nuggets deep frying. The 3-MCPD esters significantly increased in the first 12 h and then decreased, whereas 2-MCPD esters increased to a maximum at 24 h (0.69–0.81 mg kg⁻¹) and then decreased. The GEs decreased with frying time and degraded to approximately 0.05 mg kg⁻¹ after 36 h in all frying oils. The correlation results showed that the 3-MCPD esters had a positive correlation with 2-MCPD esters (R = 0.910), so 3-MCPD esters could be an indicator of the presence of MCPD esters in frying oils. Strong correlations were found between MCPD esters and the peroxide values and p-anisidine values, indicating that changes in MCPD esters may be related to oil oxidation. These results may improve our understanding of MCPD esters and GEs in frying oils and find ways to control them during frying.     

Amino Acid and Vitamin Composition of Raw and Cooked Horse Mackerel

Amino acid, vitamin (A, E, B₁, B₂, B₃ and B₆), and proximate composition were determined in raw and cooked horse mackerel. The changes in amino acid, vitamin, and proximate content were found to be significant for all cooking methods (frying, grilling, and steaming). Cooking did in general significantly increase the contents of essential, semi-essential, and other amino acids compared to raw fish species. Amino acid contents of grilled mackerel were significantly higher (p < 0.05) than those found in fried and steamed mackerel. The A, E, B₂, and B₆ vitamin content of fried horse mackerel was found to be significantly (p < 0.05) higher than the grilled and steamed samples. The B₁ content of steamed and B₃ content of grilled were found higher than the other cooked samples. Moisture, protein, fat, ash, and carbohydrate contents of cooked fish ranged between 56.52% to 61.34%, 20.79% and 23.93%, 13.44% and 19.61%, 1.70% and 2.47%, and 1.02% and 4.36 %, respectively. Fried fish had intermediate fat values, while grilled and steamed fishes had a comparatively low value.     

Porosity determination of deep‐fat‐fried coatings using pycnometer (Fried batter porosity determination by pycnometer)

The effect of processing conditions such as frying time and temperature, and batter formulation on pore development in deep‐fat fried chicken nuggets coatings were studied using helium pycnometer method. Chicken nuggets with preformed and laboratory prepared batter coatings were fried at temperatures between 170 and 190 °C for a time range between 0 and 240 s. There was significant (P < 0.05) effect of frying temperature and batter formulation on porosity. Porosity increased with frying time and temperature, and ranged between 2.15 and 47.92% for the preformed batter and 9.96 and 54.76% for the formulated batters. Apparent and bulk densities of the preformed batters increased and decreased with frying time, respectively, but both declined gradually with increasing frying temperature. As the level of rice flour in the formulation increased, apparent and bulk densities also increased. Batter formulation and frying temperature significantly (P < 0.05) influenced the variation in moisture and fat content of the fried batter. Porosity demonstrated positive and negative correlation with fat uptake and moisture loss, respectively, for all the batter coatings.