Analysis of Volatile Compounds in Traditional Chinese Fish Sauce (Yu Lu)

Yu lu is a traditional Chinese fish sauce with a strong and distinctive odor. The volatile compounds in the fish sauce made from anchovy (Engraulis japonius) and the snakehead fish (Channa asiatica) were isolated by simultaneous distillation–solvent extraction (SDE) and analyzed by gas chromatography (GC) and mass spectrometry (MS). About 70 volatile compounds were identified, including 20 acids, 4 carbonyls, 14 nitrogen-containing compounds, 14 hydrocarbons, 8 esters, and 3 sulfur-containing compounds. The major contributors to the characteristic odor of the fish sauce are dimethyl disulfide, dimethyl trisulfide, propanoic acid, butanoic acid, 3-(methylthio)-propanol, 2-methylbutenal as well as some nitrogen-containing compounds. Nitrogenous and sulfurous compounds in the fish sauce made from anchovy were more abundant than the fish sauce made from snakehead, while snakehead fish sauce had a greater amount of volatile fatty acids. 3-(Methylthio) propanol could be another important contributor to the distinctive odor of fish sauce.     

Selection of Universal Primers for PCR Quantification of Total Bacteria Associated With Fish Fillets

An optimal universal primer pair DG74/RW01 for quantitative PCR detection of the mixed bacterial flora from fish fillets was selected from five pairs of primers. The minimum detection limits with GelStar? and ethidium bromide (EB) used as agarose stains for DNA bands with these primers were found to be 5 and 1 × 10² CFU/PCR, respectively. The liner range of DNA amplification was from 50 to 1 × 10⁵ with GelStar? and from 5 × 10² to 1 × 10⁵ with EB.     

Selection of Universal Primers for PCR Quantification of Total Bacteria Associated With Fish Fillets

An optimal universal primer pair DG74/RW01 for quantitative PCR detection of the mixed bacterial flora from fish fillets was selected from five pairs of primers. The minimum detection limits with GelStar™ and ethidium bromide (EB) used as agarose stains for DNA bands with these primers were found to be 5 and 1 × 10² CFU/PCR, respectively. The liner range of DNA amplification was from 50 to 1 × 10⁵ with GelStar™ and from 5 × 10² to 1 × 10⁵ with EB.     

不同产地传统鱼露风味特征差异分析

为研究不同产地鱼露的风味特色,采用顶空-气相离子迁移谱(gas chromatography-ion mobility spectrometry,GC-IMS)、电子鼻、顶空固相微萃取-气相色谱-质谱(headspace solid phase microextraction gas chromatography-ma...     

啤酒有害菌的PCR检测和SYBR Green实时PCR定量

啤酒有害菌是一些能在啤酒中存活并使啤酒的外观和风味发生改变的细菌,对其进行快速检测和定量是啤酒生产急待解决的问题。我们从华润雪花啤酒（中国）有限公司各工厂提供的样品中分离到28株啤酒有害菌,16S rDNA序列的系统进化分析表明,其中26个菌株属于乳杆菌属（Lactobacillus spp．）、1个菌株为明串珠菌属（Leuconostoc spp．）,1个菌株为片球菌属（Pediococcu sp．）。根据酒花（hop）抗性基因horA、horB和horC的保守序列设计了扩增这3个基因的PCR引物,用这些引物对28株啤酒有害菌进行了常规PCR检测,检出率分别为89％、79％和75％,用hor A—horC双引物进行检测,检出率为100％。用SYBR Green实时定量PCR技术,以horA基因为靶序列,建立了对啤酒有害菌的细胞数进行快速定量的新方法,用该方法测定的污染啤酒样品中有害菌的浓度与平板培养法相近。     

嗜盐性蛋白酶产生菌Virgibacillus sp. P-4的筛选鉴定及其特性分析

利用酪蛋白琼脂平板从传统虾酱中分离嗜盐性蛋白酶产生菌,经形态学、生理生化和分子生物学鉴定,确定该菌隶属于枝芽孢杆菌属Virgibacillus sp.P-4,并用此菌为后续研究菌株。结果表明,该菌最适生长温度为30~37℃,最适生长NaCl质量分数为5%~15%;所产胞外蛋白酶在20~50℃条件下酶活力较高且保持稳定,最适反应温度为40℃,当NaCl质量分数为15%时酶活力达到最高,并且所产胞外蛋白酶种类可能不只一种,但不包含巯基蛋白酶;通过分析酶解液中游离氨基酸释放速率,预测其酶切位点为Phe-、Tyr-、Lys-、His-、Pro-及Leu-。     

温度对传统鱼露发酵后期品质的影响

利用保温方法促进传统发酵后期鱼露的熟化,分析保温过程中的总可溶性氮(TSN)、氨基酸态氮(AA-N)、挥发性盐基氮(TVB-N)含量、pH值、细菌总数的变化情况,利用顶空进样法(HS)结合GC-MS法和感官分析法研究保温过程中鱼露风味的变化规律。结果表明,保温法可促进鱼露熟化,其TSN、AA-N含量随保温温度升高和保温时间的延长逐渐增加,TVB-N含量、pH值、细菌总数变化较小,描述性定量感官分析表明传统鱼露发酵后期保温能显著性改善鱼露风味,60℃保温后鱼露风味整体可接受性较好。顶空进样法结合GC-MS分析认为经60℃保温8d后鱼露中特征香味的挥发性酸、2-甲基丙醛、2-甲基丁醛、二甲基三硫等含量有显著性增加。2年鱼露60℃保温8d后风味物质的种类及含量达到3年鱼露水平。     

Real-Time TaqMan PCR for Rapid Detection and Quantification of Coliforms in Chilled Meat

Coliforms are a major group of bacteria associated with spoilage of refrigerated pork. It is necessary to develop an efficient and fast method to detect total coliforms in chilled pork because the traditional methods are laborious and time-consuming. In this study, a quantitative real-time polymerase chain reaction (qRT-PCR) targeting the lacZ gene was developed for rapid enumeration of coliforms from chilled pork. Of the 106 strains tested, 35 coliform strains and one Shigella sonnei strain were correctly identified compared with 70 control strains which failed to amplify. Detection sensitivity was 112 CFU/g. The assay was able to detect and accurately quantify the total coliforms in chilled meat within 2 h without preenrichment. The results indicate that the real-time PCR is an efficient and time-saving method that could be adopted by the meat industry to detect coliforms to replace the traditional most probable number and the rapid coliform count plate methods.     

Histamine Formation in Fish Sauce Production

ABSTRACT: The formation of histamine in fish sauce made from Stolephorus sp was studied. In the first experiment, fish were iced on board and mixed with salt at the factory, while in the second experiment fish were mixed with salt on board collection vessels. Eight batches were fermented for 12 mo. Histamine levels increased during fermentation to 22 to 159 and 589 to 686 ppm in the first and second experiments respectively. Good correlation between histamine levels in raw material and final products was found. It was concluded that histamine was formed both in the raw material and during fermentation. It was speculated that histidine decarboxylase enzymes formed prior to fermentation produced histamine during fermentation.     

Validation of a Real-Time PCR On-Site Quantification Method for MON810 Maize

A rapid on-, or near-site, quantitative method for use as a pre-harvest predictive decision, or co-existence monitoring, tool for adventitious genetically modified (GM) presence has been developed. Based on a laboratory-based protocol for real-time (RT) quantification of the MON810 GM event in maize kernels, the duplex RT polymerase chain reaction method was constructed around the portable Cepheid SmartCyclerII platform, requiring only modest support infrastructure for field application. Validation through an international ring trial showed good compliance with minimum assay performance requirements as defined by the European Network of GMO Laboratories (RSD_r = 18.5%; RSD_R = 32.8; Bias = 26.7%).     

实时荧光定量PCR技术在乳酸菌定量检测中的应用

与传统的菌落计数、杂交技术及PCR技术等相比,实时荧光定量PCR技术作为一种检测和定量微生物的方法,具有较高的灵敏度及可重复性,而且反应过程快速,污染较小.作者综述了实时荧光定量PCR技术的定量原理,荧光检测物质,目的基因序列以及其特点,并且列举了在乳酸菌定量检测中的应用,同时对其应用前景进行了展望.     

Predominant Bacteria Diversity in Chinese Traditional Sourdough

The purpose of this study was to identify the major bacteria in Chinese traditional sourdough (CTS). Five CTS samples (Hn‐87, Sx‐91, Gs‐107, Hf‐112, and Hr‐122) were collected from different Chinese steamed breads shops or private households. The total bacterial DNA was extracted from sourdough samples and sequenced using Illumina Hiseq 2000 system. Illumina tags were assigned to BLASTN server based on 16S rRNA libraries to reveal a genetic profile. Phylogenetic analysis revealed that the bacteria in traditional sourdough samples were dominated by the genera Leuconostoc and Lactobacillus. Beta diversity analysis, principal component analysis, and cluster analysis compared the bacterial differences in traditional sourdough samples. The results showed that Leuconostoc, Lactobacillus, and Weissella were the predominant genera among the 5 samples. This differentiated the sourdoughs into 3 typologies, namely, 1) Gs‐107 and Sx‐91, 2) Hr‐122 and Hn‐87, and 3) Hf‐112. This study identified 3 unique major bacteria genus in CTS bread ecosystems.     

Purification and Characterization of a Halotolerant Alkaline Serine Protease from Penicillium citrinum YL-1 Isolated from Traditional Chinese Fish Sauce

A halotolerant alkaline serine protease from Penicillium citrinum YL-1 which was isolated from traditional Chinese fish sauce was purified by ammonium sulfate precipitation, dialysis, and DEAE 52-Cellulose column, thereby resulting in a 4.66-fold increase in specific activity (110.68 U/mg). The molecular weight (MW) was estimated to be 32.27 kDa using SDS-PAGE analysis. The protease exhibited optimal activity toward the substrate casein at pH 8.0 at 40°C and was stable at pH 6.0–8.0 and 4–30°C. Activity was inhibited by NaCl and retained at 28.3, 21.4 and 18.1% of the initial activity after incubation for 6 h at 20, 25 and 30% NaCl concentrations, respectively. The enzyme was stimulated by Mn²⁺ and inhibited by K⁺, Ca²⁺, Zn²⁺, Mg²⁺, Fe²⁺, and Fe³⁺. K_m and V_max of the protease for casein were 1.93 mg/ml and 56.81 μg/(min·ml), respectively. Protease activity was strongly inhibited by phenylmethyl sulfonylfluoride (PMSF), which confirmed the serine protease nature of the enzyme. The protease can hydrolyze tilapia protein in the absence or presence of NaCl (5–30%), thus suggesting that this protease is more halotolerant than the protease from other bacteria with high salinity resistance based on the current literature. These properties make the halotolerant alkaline serine protease a suitable candidate enzyme for fish protein hydrolysis during fish sauce fermentation.     

食品接触材料中3种致病菌的多重荧光PCR检测

建立并优化食品接触材料中金黄色葡萄球菌、沙门氏菌和副溶血性弧菌3种致病菌的多重实时荧光聚合酶链式反应(polymerase chain reaction,PCR)检测方法,评价此方法的特异性和灵敏度,并模拟阳性样品进行检测。结果显示,该方法特异性良好,检测灵敏度均能达到10~3 CFU/mL,为食品接触材料的微生物检测提供技术保障。     

熔解曲线结合RT-PCR在餐饮食品中对5种致病菌的检测

建立快速检测餐饮食品中沙门氏菌、金黄色葡萄球菌、单核增生李斯特氏菌、大肠埃希氏菌O157:H7及副溶血性弧菌5种致病菌的实时聚合酶链式反应体系(real-time polymerase chain reaction,RT-PCR)。通过增菌时间的比较,调整RT-PCR反映体系中的退火温度,建立5种致病菌相同的检测体系。试验结果表明,5个目标菌达到检测灵敏度的最短增菌时间范围为2 h～8 h,5种致病菌的试验灵敏度范围为7.4×10 CFU/mL～2.4×103CFU/mL。5种目标菌的熔解温度Tm值分别为沙门氏菌87.32℃,金黄色葡萄球菌79.57℃,单核增生李斯特氏菌82.02℃,大肠埃希氏菌O157:H7 82.24℃,副溶血性弧菌87.15℃。试验建立的RT-PCR快速检测反应体系,与常规微生物检测方法相比,有效地缩短了检测时间,且灵敏度与特异性均能满足检测要求。     

鱼露及加工技术研究进展

介绍了鱼露发酵生产的基本情况,并从安全性、生物活性、风味以及快速发酵生产工艺4个方面说明发酵法生产鱼露的研究进展;特别说明了鱼露中存在致癌性前体成分———亚硝基化合物以及多种生物活性成分;介绍了目前对鱼露中挥发性成分和非挥性成分风味成分的鉴定研究情况,指出了快速发酵工艺给鱼露风味带来的负面影响。     

RT-PCR结合高分辨率熔解曲线对两种致病菌的快速检测

为建立食品中金黄色葡萄球菌、单核增生李斯特氏菌的双重快速检测方法。用缓冲蛋白胨水(buffered peptone water,BPW)对两种目标菌进行增菌培养,采用直接提取法提取样本DNA,比较实时聚合酶链式反应体系(real-time polymerase chain reaction,RT-PCR)中的退火温度,调整高分辨率熔解曲线(high-resolution melting curve,HRM)分析条件,建立同时检测金黄色葡萄球菌、单核增生李斯特氏菌的方法。结果表明,PCR扩增最佳退火温度为58℃,两种目标菌的Tm值分别为金黄色葡萄球菌77.05℃,单核增生李斯特氏菌79.39℃;试验灵敏度分别可以达到102、103 CFU/g。     

鱼露发酵技术的研究进展

统计了国内外鱼露相关研究概况,重点介绍了鱼露的快速发酵、风味改善、功能性研究及安全性保证等方面的研究成果,为鱼露的深入研究及其快速工业化、规模化、标准化生产提供依据。     

不同原料鱼酿造鱼酱油的挥发性风味差异

采用不同原料鱼在传统工艺下酿造鱼酱油,用气相色谱-质谱联用和电子鼻测定分析其挥发性风味化合物,并与风味品质等级最高的原汁鱼酱油进行比较。结果表明:不同原料鱼鱼酱油的挥发性化合物种类和数量差异很大,蓝圆鯵鱼酱油检出的挥发性化合物最为丰富,有17种,其中包括含硫化合物3种、醛6种、酸3种,鱼酱油特征挥发性化合物10种,表现出较好的挥发性风味特性。其次是绿鳍马面鲀鱼酱油,共检出对特征气味有贡献的化合物9种。鯷因其易腐败特性,故而被多用于鱼酱油生产,但其特征挥发性化合物种类数量却不是最丰富,尤其是鯷的幼鱼——丁香鱼的挥发性化合物种类最少。本研究表明,蛋白质含量高,氨基酸总量高,尤其是含硫氨基酸含量高的原料鱼较易形成鱼酱油特征气味,而脂肪含量过高的原料鱼则不适合进行鱼酱油生产。     

鱼肉辣椒酱开发研究

辣椒酱是人们生活中的重要调味品。草鱼肉质鲜美、营养丰富。鱼肉辣椒酱是以干辣椒、淡水鱼为主要原料制作而成。以干辣椒的添加量为25%,鱼丸的添加量为18%,鱼丸是以88%的草鱼肉糜加入玉米淀粉5%、盐3%、猪油4%制作而成。成品主料分明,色泽鲜艳,口感俱佳,是一款营养价值高的辣椒酱。