食品加工工艺对大豆内源基因降解变化规律的影响

本文以转基因大豆和非转基因大豆为试验材料，运用定性PCR技术分析了磨浆、煮浆、调配、均质、点浆、杀菌、喷雾干燥等豆腐、豆奶、豆粉三种豆制品中关键加工工艺对大豆内源基因lectin的影响，探讨了转基因大豆加工食品在不同加工过程中DNA降解程度的变化。研究结果表明，大豆内源基因在三种加工食品中的各个加工过程中都会受到不同程度的破坏。在豆腐、豆奶、豆粉的加工过程中，片段大小为1883bp的lectin基因仅能在原料中检测到；磨浆、煮浆、均质等工艺，使lectin基因降解至1000bp以下；随着进行的点浆、高温杀菌或喷雾干燥等工艺对lectin基因的降解产生更显著的影响，豆腐终产品中lectin基因的片段大小在500bp以下，豆奶、豆粉中lectin基因片段大小仅为200bp左右。     

干热加工工艺对大豆转基因成分及调控元件的影响

以转基因大豆为材料,运用定性PCR方法研究干热加工工艺对转基因大豆内源基因Lectin、外源基因Cp4epsps以及启动子CaMV35s和终止子Nos的影响。结果发现:大豆经过130℃干热加工3min后,内源基因Lectin降解到407bp以下;经过120℃加热9min后,外源基因Cp4 epsps降解到408bp以下;干热加工对启动子的片段长度并没有影响,而当加工条件达到130℃加热9min时,终止子125bp的片段会产生降解。结果表明,不同温度和时间的干热加工工艺对大豆转基因成分及调控元件的降解均有不同程度的影响。     

干热和湿热工艺对大豆转基因成分及调控元件影响的比较研究

以转基因大豆为试验材料,运用定性PCR的方法研究了干热和湿热两种制粒加工工艺对转基因大豆内源基因Lectin、外源基因Cp4 epsps以及启动子和终止子的影响。结果发现大豆经过130℃干热处理3 min或100℃湿热处理15 min后,内源基因降解到407 bp以下;经过120℃加热9 min或100℃湿热处理15 min后,外源基因降解到408 bp以下;干热处理对启动子的片段长度并没有影响,而当加工条件达到130℃干热9 min时,终止子125 bp的片段开始会产生降解;当100℃、3 min湿热处理后启动子和终止子都会产生降解。结果表明,不同干热和湿热制粒工艺对大豆转基因成分及调控元件的降解均有不同程度的影响。     

食品中转基因大豆成分的定性和定量检测

为建立食品中转基因成分的定性定量分析，运用传统的定性PCR方法检测大豆加工产品中转基因成分的存在，运用Taqman探针技术，对存在的转基因成分进行准确定量。对于定量过程中由于扩增效率的不同造成的误差，通过大豆的内源基因Lectin进行校正，根据△Ct值对应于校正曲线计算出转基因大豆的含量。本方法灵敏度达到0．1％，误差范围小于30．0％。可用于转基因大豆的监测管理。     

粉碎和膨化工艺对大豆转基因成分及调控元件的影响

以转基因大豆为试验材料,运用定性PCR的方法研究了粉碎、膨化两种加工工艺对转基因大豆内源基因Lectin、外源基因Cp4 epsps以及启动子和终止子的影响。结果表明,粉碎和膨化加工工艺对大豆转基因成分及调控元件的降解有不同程度的影响。     

转Bar、Bt基因双抗大米外源基因在食品加工过程中稳定性的研究

旨在了解转Bar、Bt基因双抗大米外源基因在酒酿和米果加工过程中的稳定性,以转Bar、Bt基因双抗大米为原料,进行了6种不同方式的加工,并针对其加工品中外源基因(包括CaMV35S启动子、Ubiquitin启动子、NOS终止子、Bar基因和Bt基因)进行不同大小片段的PCR扩增。结果表明,实验中长度小于200bp的片段均具有较高的GC含量(NOS终止子除外)和良好的稳定性。      

在食品加工过程中控制淀粉粘度的重要性：淀粉和酱油间相互作用的研究

在亚洲，酱油通常用于含淀粉食品的加工中。不同的酱油产品在组成上相差很大，特别是一些影响淀粉糊化的成分，如ＮａＣｌ含量。本项目研究了添加１６％酱油对商品玉粉糊化性质的影响，用ＤＳＣ法测定了淀粉、水及 酱油混合物的糊化温度。快速粘度测定仪采用循环两次加热和冷却的程序。，     

市场对转基因食品的认知、接受程度对政府部门在转基因食品安全监管方面的影响分析——对广州市大型超市转基因食品消费情况的调查研究

通过对广州市四大老城区的近20家大型超市货架上的转基因食品标签、价格的情况进行调查,并分别对各大超市采购负责人和消费者关于转基因食品的认知、接受程度等情况的调查,了解并得到市场对转基因食品的认可接受的基本情况,并从中分析影响这些调查结果的主要因素.在此基础上,结合我国目前在转基因食品安全管理的有关法规,还给相关的政府部门提出了如何加强转基因食品安全知识宣传教育和监管等政策建议.     

转基因大豆的PCR-免疫层析筛查方法研究初探

目的建立转基因大豆的PCR-免疫层析（PCR—ICT）快速筛查新技术。方法利用转基因植物通常含有的CaMV35S启动子作为转基因成分的筛查标记，根据其序列设计特异性引物和探针，分剐用生物素和地高辛标记，用胶体金免疫层析技术检测并鉴定PCR产物。结果用新建立的PCR—ICT方法可以检出含0．5％转基因大豆的标准品，对大豆样品的检测结果与琼脂糖凝胶电泳检测结果一致。结论PCR—ICT方法通过DNA杂交和金标显色来同时检测、鉴定PCR产物，可以简便、快速地筛查转基因产品。     

Interactions between whey soybean protein (WSP) and beta-conglycinin (7S) during the formation of protein particles at elevated temperatures

In this study, the amount, size, calcium sensibility, and composition of heat-induced protein particles in the mixture of beta-conglycinin (7S) and whey soybean protein (WSP) dispersion are compared with those of 7S and WSP dispersion to investigate the interactions between WSP and 7S during heating. The addition of 7S prevents WSP from forming large protein particles which can be precipitated by centrifugation at 10,000g for 10 min. The protein in the heated mixture of 7S and WSP (7S/WSP = 1/1) coagulates at higher calcium concentrations than that in the mixture of heated 7S and heated WSP at a ratio of 1/1. This result strongly indicates that 7S and WSP interact with each other during heating and form complex protein particles which have special surface properties that are different from individual 7S and WSP protein particles. Particle size distribution analysis has also shown that 7S prevents WSP from forming larger protein particles during heating. SDS-PAGE analysis shows that lipoxygenase (LOX), beta-amylase, and lectin of WSP and the beta subunit of 7S tend to form a particulate fraction, while the KTI, alpha, and alpha′ subunits tend to form a soluble fraction. WSP, 7S, and their mixture have been heated at 60, 65, 70, 75, 80, 85, 90, and 95 °C for 10 min, and ultracentrifugation analysis shows that about 77–85% of the protein particles were formed at 65–75 °C in all three dispersions. SDS-PAGE analysis indicates that LOX and β-amylase have been denatured and that they have participated in the formation of protein particles when heated within 65–75 °C, while lectin has begun to participate in particle formation at above 85 °C. It is concluded that WSP plays an evident role in the formation of protein particles in soymilk during heating.     

不同工序油茶籽油中苯并(α)芘含量的变化

为控制油茶籽油生产过程中苯并(α)芘含量的增加,使油茶籽油质量符合国家食用安全标准要求,从原料质量的把控开始,对油茶籽油生产的各个环节进行苯并(α)芘含量的跟踪测定,确定油茶籽油生产过程中引起苯并(α)芘含量增加的关键环节,探讨控制方法。结果表明:霉变的油茶籽、压榨工艺控制不当是引起油茶籽油生产过程中苯并(α)芘含量大幅增加的因素,优选具有吸附苯并(α)芘作用的脱色剂是降低油茶籽油中苯并(α)芘含量的一个好方法。     

Stability of electronic nose (e-nose) as determined by considering date-pits heated at different temperatures

Variability and sensitivity of a portable electronic nose (32 sensors) was assessed by considering different variables for measurement (i.e., reference, standard, first and second purges, sample draw time, waiting time for the volatiles released in the headspace, and mass of sample or headspace volume of the jar containing sample). In this study, dried date-pits were used a model sample. The highest stability was achieved when both reference and standard (i.e., dried date-pits, no heating treatment) were used before test sample measurement. Higher sample draw time more than 10 s significantly decreased the stability, whereas optimum second purge was observed at 50 s. Optimum time to generate volatile was observed as 24 h. A sample of 100 g increased the signal intensity compared to the 50 g sample for the 60°C and 100°C treated samples, while an opposite trend was observed for the 150°C treated sample. Finally, the responses of volatile components in date-pits heated at different temperatures (60°C, 100°C, and 150°C) were measured using the optimum operating conditions. Principal component analysis explored the relationships between the volatile features and classified date-pits heated at different temperatures. The results showed that an electronic nose was able to classify date-pits based on their volatile components generated by different degrees of heating (93.3% accuracy).     

Comparison of fermented soybean paste (Doenjang) prepared by different methods based on profiling of volatile compounds

Abstract: In this study, 2 different extraction methods, namely solvent‐assisted flavor evaporation (SAFE) and solid‐phase microextraction (SPME), were employed to investigate the comprehensive volatile profile of Doenjang (one of Korean fermented soybean pastes) efficiently. Quantitatively, major volatiles of Doenjang isolated by SAFE were 3‐methylbutanoic acid, butanoic acid, 3‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one (maltol), ethyl 2‐methylbutanoate, 2‐methylpropanoic acid, tetramethylpyrazine, and 4‐ethyl‐2‐methoxyphenol, while ethanol, ethenylbenzene, ethyl benzoate, ethyl linoleate, ethyl acetate, ethyl butanoate, tetramethylpyrazine, and ethyl 2‐methylpropanoate extracted by SPME. In addition, volatile profiling that applied principal component analysis to gas chromatography‐mass spectrometry datasets allowed Doenjang samples that had been prepared using different traditional and commercial methods to be discriminated, and the volatile compounds that contributed to their discrimination were assigned. The major volatiles that were related to differentiation of traditional and commercial Doenjang samples were 2‐pentylfuran, 4‐ethylphenol, dihydro‐5‐methyl‐2(3H)‐furanone, butanoic acid, pyrazines (for example, 2‐ethyl‐5‐methylpyrazine and 2,3‐dimethylpyrazine), esters (for example, ethyl 4‐methylpentanoate and diethyl succinate), maltol, dimethyl disulfide, 2‐ and 3‐methylbutanal, hexanal, 4‐vinylphenol, and ethanol.     

Comparing different gas chromatographic methods for the quantification of bisphenol A (BPA) trace levels in paper and cardboard products from the market

Bisphenol A (BPA; 4,4?-(propane-2,2-diyl)diphenol), a suspected endocrine disruptor with weak estrogenic activity, is used in a variety of consumer products, including paper and cardboard products used as food contact materials. The present study compared four different gas chromatographic methods for the analysis of BPA in paper and cardboard food packages. Eighteen different food packages were extracted and BPA was determined using two different derivatisation reactions – trimethylsilylation with N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) and halide alkylation with pentafluorobenzoyl chloride (PFBOCl) – and four different separation and detection techniques. The BSTFA derivatives were quantified with (1) GC-MS in single-ion monitoring (SIM) mode with electron ionisation (EI-GC-MS) and (2) GC-MS/MS in multiple reaction monitoring (MRM) mode using electron ionisation (EI-GC-MS/MS); while the PFBOCl derivatives were quantified with (3) GC-MS using electron ionisation (EI-GC-MS) as well as (4) GC-MS with negative chemical ionisation (NCI-GC-MS). All developed methods showed good linearity (R² > 0.9938), precision (CV < 4.5% for reproducibility; CV < 2.2% for repeatability) and sensitivity, with limits of detection (LODs) between 0.02 µg kg^?1 for the pentafluorobenzoyl derivatives measured with the NCI-GC-MS method and 6 µg kg^?1 for the pentafluorobenzoyl derivatives determined with EI-GC-MS. Levels of BPA in the samples were in agreement for all methods, ranging from values below the limit of quantitation (LOQ) to 11.9 mg kg^?1 paper. In a last step, the maximum potential migration into food products was calculated for all tested paper and cardboard samples, assuming a ‘worst case’ scenario of 100% migration.     

Influence of roasting and different brewing processes on the ochratoxin A content in coffee determined by high-performance liquid chromatography-fluorescence detection (HPLC-FLD)

A rapid and reliable procedure has been developed for the determination of ochratoxin A (OTA) in green and roasted coffee. The method consists of extraction of the sample with methanol–5% aqueous sodium hydrogen carbonate/1% PEG8000 (20:80), followed by immunoaffinity column (IAC) clean-up and, finally, high-performance liquid chromatography (HPLC) determination with fluorimetric detection. Mean recoveries for green and roasted coffee spiked at different levels ranging from 94 and 105% were obtained. The limit of determination (S/N = 3) was 0.032 ng g^?1 and the precision (within-laboratory relative standard deviation) was 6%. The method described has been used to assess the influence of roasting and different brewing processes on OTA content in commercial lots of green and roasted coffee. The results provided evidence that roasting led to a significant drop on OTA levels (65–100%). Also, the way coffee is prepared affects the OTA content: brewing using a Moka Express (Italian coffee) led to a significant reduction of OTA concentration (50–75%) since hot water stays in contact with coffee for a short time. On the contrary, Turkish coffee-making (infusion for about 10 min) cause poor reduction in OTA.     

Role of lipid deterioration on the quality of aquatic products during low-temperature storage: a lipidomics-based study using large yellow croaker (Larimichthys crocea)

This work investigated the effects of different storage periods (0 day, 90 days, 120 days) on the quality of large yellow croaker oil. The lipomics of large yellow croaker oil was quantitatively detected by GC-MS, the content of triglyceride in large yellow croaker oil reached 52.56% at 0 day. With the extension of storage time, the content of large yellow croaker oil components decreased gradually. Differential lipid histogram clearly indicates that the extension of the storage period will affect the change of fish oil, due to the rise in the temperature of large yellow croaker oil; the color of the hot map is bright from the dark. Additionally, the fatty acid composition and volatile components were measured. At 120 days, the decomposition rate of lipid molecular in large yellow croaker oil is increased by oxidation of unsaturated fatty acids, and its oxidised metabolite produced small substance such as aldehydes, ketones, alcohols, and acids. During storage, the waxy, fat, and floral flavour in the oil aroma of large yellow croaker oil decreased gradually, while the yeast flavour and oil flavour increased gradually. These results provide insights for the study of lipid transformation and quality of large yellow croaker oil during different storage.