Analysis of the inhibition of food spoilage yeasts by vanillin

The antimicrobial potential of vanillin, the major component of vanilla flavour, was examined against the growth of three yeasts associated with food spoilage, Saccharomyces cerevisiae, Zygosaccharomyces bailii and Zygosaccharomyces rouxii. Minimum inhibitory concentration (MIC) values of 21, 20 and 13 mM vanillin were determined for the three yeast strains, respectively. The observed inhibition was found to be biostatic. During fermentation, the bioconversion of sub-MIC levels of vanillin in the culture medium was demonstrated. The major bioconversion product was identified as vanillyl alcohol, however low levels of vanillic acid were also detected. Neither the vanillyl alcohol nor the vanillic acid was found to be antagonistic to yeast cell growth. The results indicate the importance of the aldehyde moiety in the vanillin structure regarding its antimicrobial activity and that the bioconversion of vanillin could be advantageous for the yeasts, but only at levels below MIC. These bioconversion activities, presumably catalysed by non-specific dehydrogenases, were shown to be expressed constitutively. It was observed that increased vanillin concentrations inhibited its own bioconversion suggesting that the activity required intact cells with metabolic capacity.     

食品中腐败酵母的实时荧光PCR鉴定

为研究食品中腐败酵母实时荧光PCR快速鉴定方法,设计和筛选出了可用于腐败酵母鉴定的多条探针和引物,并建立了针对酿酒酵母、鲁氏接合酵母、斯巴达克毕赤酵母和布鲁塞尔德克酵母等4种腐败酵母菌的实时荧光PCR鉴定方法。用文中建立的方法对从糕点、蜂蜜、饮料等市售食品中分离出的60余株酵母菌进行了鉴定,发现其中4株为酿酒酵母,21株为鲁氏酵母,其他为与上述4种不同的酵母。以实时荧光PCR方法鉴定酵母,全过程仅需约3 h,与常用的生化鉴定方法相比,简化了鉴定步骤,提高了鉴定准确性,缩短了鉴定时间。     

Opportunities for mitigating pathogen contamination during on-farm food production

Fruits, vegetables, and meat are susceptible to contamination by foodborne pathogens at many points from production through preparation in the home. This review will largely highlight approaches and progress made in the last five years to address strategies to reduce pathogen contamination in animal production but will also touch on the emerging field of preharvest produce food safety. Mitigation strategies can be divided into those that address pathogen reduction in the environment and those that target reduction/elimination of pathogen contamination in animals or plants. The former strategy has been encompassed in studies evaluating sanitation treatments of facilities as well as in numerous epidemiologic risk assessment studies (both on-farm assessments and computer simulation models) that identify management practices that impact pathogen prevalence in animals. Interventions to significantly reduce pathogen exposure via feed or water are dependent on their role as a significant contributor to pathogen contamination in the animal production system. In addition, inconsistent results obtained with interventions of dietary additives or formulation modifications (grain versus forage; inclusion of distiller's grains) on pathogen prevalence in animals have been attributed to a range of factors including target organism, grain type, level of inclusion, the animal's health or stress level, and ability to survive the gastric acidic conditions. Recent attempts to microencapsulate organic acids or bacteriophage within feed have met with only marginal improvements in reducing pathogen carriage in animals but this approach may have greater potential with other antimicrobial additives (i.e., essential oils). Bacteriophage therapy, in general, can significantly reduce pathogen carriage in animals but based on its transient nature and the potential for development of phage-resistant subpopulations, this approach should be administered to animals just prior to slaughter and preferably to animals that are suspected “super-shedders”. Other promising on-farm intervention approaches have included breeding for pathogen resistance, vaccines, and dietary bacteriocins. To optimize interventions on a cost basis, studies have also determined that application of dietary interventions at specific time points in the animal's production cycle is a useful strategy to reduce pathogen carriage (e.g., probiotics to fertilized eggs and acidified feed to fattening swine). In conclusion, applicable management and intervention strategies may vary depending on the type of food under production; however, it is important to consider from a holistic view how any new intervention strategies will affect the overall production system in order to maintain a successful, efficient food production environment.     

Activity of essential oils from Mediterranean Lamiaceae species against food spoilage yeasts

The essential oils from aerial parts of Melissa officinalis, Lavandula angustifolia, Salvia officinalis, and Mentha piperita were analyzed by gas chromatography and gas chromatography-mass spectrometry. Their antimicrobial activities were evaluated against five food spoilage yeasts, Torulaspora delbrueckii, Zygosaccharomyces bailii, Pichia membranifaciens, Dekkera anomala, and Yarrowia lipolytica. Saccharomyces cerevisiae was also used as a reference. The oils were preliminarily screened by a disc diffusion technique, with the most active being the oil from M. officinalis. MICs were determined by the broth dilution method, and the main components of the oils were also tested by this method. The essential oil of M. officinalis at 500 microg/ml completely inhibited the growth of all yeast species. The main component of the oil of M. officinalis is citral (neral plus geranial) (58.3%), which showed a marked fungitoxic effect, contributing to its high activity.     

水果腐败传感监测系统设计与试验

目的：解决水果腐败多气体动态监测和早期预警的难点。方法：设计了气体传感器模块、数据采集模块等模块,开发了检测软件,集成研制了基于气体传感器阵列检测系统。以苹果为验证对象,探析了苹果腐败前气体传感器的响应差异及变化规律。结果：建立了线性判别分析、K-最近邻和反向传播人工神经网络（BP-ANN）3种苹果腐败前天数的判别模型,其中BP-ANN识别率达99%;通过联合区间、遗传算法、模拟退火、蚁群算法和竞争自适应重加权抽样法（CARS）5种变量筛选方法结合偏最小二乘法（PLS）筛选特征变量,建立了腐败前天数定量预测模型,CARS-PLS模型的预测效果最优,相关系数可达0.974。结论：基于气体传感器技术的水果腐败检测是可行的,为水果腐败检测系统的研发提供参考。     

葡萄酒病害相关酵母的分离与鉴定

利用3种培养基和3种分离方法,从贺兰山东麓葡萄酒产区发生葡萄酒病害的5款酒样中分离获得23株酵母菌株。经形态学鉴定,初步将所分离的酵母菌归为4种培养类型;26S rDNA D1/D2区序列分析结果表明,4种培养类型的酵母分属于3个属3个种,分别为酿酒酵母（Saccharomyces cerevisiae）、葡萄汁有孢汉逊酵母（Hanseniaspora uvarum）和乳酪隐球酵母（Cryptococcus friedmannii）。     

酿制木瓜果酒的酵母菌选种研究

以木瓜和市售各种带酒味的腐烂水果表面为分离源，分离得到68株酵母菌，经过3级筛选，获得3株适合酿造木瓜果酒的酵母菌，编号分别为Y-3-1、Y-4-1和Y-9-1。经感官评定，采用这3株菌所酿制的木瓜果酒明显优于常用的酿酒用耐高温活性安琪酵母。这3株菌适合于25℃发酵，经初步鉴定均为酵母属（Saccharomyces sp．）。     

On-farm sources of microbial contamination of persimmon fruit in Japan

Potential sources of microbial contamination for persimmon fruit during growing and harvesting in the 2005 season were investigated to provide a baseline to design the good agricultural practices program for persimmons in Japan. Microbial counts in the peel of persimmon fruit during production season were close to or below 2.4 log CFU/g for bacteria and 3.0 log CFU/g for fungi but were above these values on harvested fruit. The counts in the flesh were below the detection level with all fruit. Bacteria and molds isolated from peel and flesh of persimmons during growing were phytopathogenic and soilborne organisms such as bacteria genera Enterobacter and Bacillus and mold genera Fusarium and Cladosporium, which were found in soil, weeds, agricultural water, and pesticide solution throughout the production season. The agricultural water was one of the most important potential preharvest sources, because Escherichia coli O157:H7 was identified from agricultural water in May, and Salmonella was detected in agricultural water, pesticide solution containing the agricultural water for the mixture, and soil after application of the pesticide solution in June. Neither of the two pathogenic bacteria was detected in any of the fruit samples. Microbial counts and diversity in the peel of persimmons at harvest increased after contact with plastic harvest basket and container, which could be sources of contamination during harvesting. Therefore, monitoring and management on-farm should focus on agricultural water and harvest equipment as important control points to reduce microbial contamination on persimmons.     

Potential sources of microbial contamination of satsuma mandarin fruit in Japan, from production through packing shed

Potential sources of microbial contamination of satsuma mandarin fruit were investigated from production through the packing shed in the 2005 season. Microbial counts in the peel and flesh during the fruit development stage were below 2.4 log CFU/g for bacteria and 3 log CFU/g for fungi, except for the peel in August and September. In the field environment, the highest microbial counts were found in fallen leaves on the ground, followed by soil, organic fertilizer, and agricultural water. Only the pesticide solution collected in July was positive for Salmonella, while no verotoxin-producing Escherichia coli was detected from any of the samples. The bacterial and mold flora in the peel comprised phytopathogenic organisms such as bacteria genus Pantoea and mold genus Mycosphaerella and soilborne organisms such as bacteria genus Bacillus and mold genus Cladosporium, which were found in soil, fallen leaves, agricultural water, and cloth mulch throughout the production season. After fruit harvest and sorting, microbial counts of the peel increased, while those of the flesh remained below the lower limit of detection. Although some of the preharvest sources could also be postharvest sources, some packing shed equipment was assumed to be postharvest sources, because Bacillus cereus was not identified from the fruit in the production field but was detected on the peel after sorting and on equipment such as gloves, plastic harvest basket, and size sorter. These results suggest that using sanitizers for agricultural water and packing sheds to prevent cross-contamination would be useful in a good agricultural practices program of the satsuma mandarin in Japan.     

我国食品中放射性污染监测调查情况概述

2011年日本福岛核事故后,由核事故导致的持续性污染尤其是食品中放射性污染仍受到极大关注。本文综述了食品中放射性核素污染的种类和研究现状、对人体健康的危害、主要检测方法及部分研究成果,并着重介绍研究了我国食品中放射性核素的监测现状与进展,为今后的研究方向做出了科学的指导并提供了理论支撑。     

控制木瓜果脯非酶褐变的研究

为了控制木瓜果脯生产和储藏过程中的非酶褐变问题,本文从生产工艺和储藏条件上着手,对木瓜果脯在不同条件下的褐变程度变化进行研究。结果表明,采用真空渗糖法和100%白砂糖的糖液组成,添加0.10%Na2SO3+0.10%异抗坏血酸钠+0.30%柠檬酸作为护色剂,并且进行真空包装,在低温下储藏,可以有效控制木瓜果脯的非酶褐变,保持原有色泽。      

Lipolytic activities of two strains of Aspergillus aculeatus associated with the spoilage of two food sources

The production of extracellular lipolytic enzymes by 2 strains of Aspergillus aculearus associated with the deterioration of peanuts and a marketed margarine in Nigeria and the effects of temperature and pH on the activities of the enzymes were investigated. Lipolytic enzymes were detected within 2 days of incubation at 35 °C in 4 out of 6 natural oils and in 3 out of 4 synthetic glycerides used irrespective of strain type. The lipolytic enzymes of both strains hydrolysed both natural oils and synthetic glycerides to free fatty acids. There was correlation between the mycelium produced to the quantity of free fatty acids produced in medium within the first 8 days of incubation. There was a general increase in mycelium production with increase in incubation period. The enzyme activities were at peak at 30-35 °C and at pH 6-7.     

Thermal inactivation of the wine spoilage yeasts Dekkera/Brettanomyces

The heat resistance of three strains of Dekkera/Brettanomyces (Dekkera anomala PYCC 5,153, Dekkera bruxellensis PYCC 4,801 and Dekkera/Brettanomyces 093) was evaluated at different temperatures between 32.5 and 55 degrees C. Thermal inactivation tests were performed in tartrate buffer solution (pH 4.0) and in wines. In the studies employing buffer as the heating menstruum, measurable thermal inactivation began only at temperatures of 50 degrees C. When heating was performed in wine, significant inactivation begins at 35 degrees C. Subsequent thermal inactivation tests were performed in buffer at various levels of pH, ethanol concentration, and various phenolic acids. Results from experiments in buffer with added ethanol suggest that the greater heat sensitivity shown in wines can be largely attributed to ethanol, although potentiation of this effect might be due to the phenolic content, particularly from ferulic acid. In the range of pH values tested (2.5-4.5), this factor had no influence in the heat inactivation kinetics. Relevant data, in the form of D and Z values calculated in the various environments, potentially useful for the establishment of regimes of thermal control of Dekkera/Brettanomyces yeasts in wine and contaminated equipment is presented.     

食品污染物监测及其健康影响评价的研究简介

为保障食品安全，“食品污染物监测及其健康影响评价的研究”被列入国家科技部“十五”攻关课题。主要研究内容为食品污染物分析质量控制研究；污染物(包括金属污染物，农药残留)监测技术研究；建立有害物质暴露危险性评估技术；生物学标志物研究。研究完成后，建立了我国与国际接轨的污染物监测网框架，提出了我国食品污染物监测分析质量控制评价原则，提高了我国污染物监测水平。绘制了我国食品污染物基本状况表。我国食品中重金属污染主要是铅污染，各年龄段铅的摄入量偏高，特别是儿童已经达到PTWI的105．6％～109．7％。说明我国食品中铅的含量偏高，应该修订国家标准。镉污染主要在鱼类，全国平均值超过国家标准，其中河南省淡水鱼的镉平均值是国家标准的近3倍，其他食品镉的污染不严重。砷、汞在食品中的污染不严重。成功地以总膳食研究为手段进行膳食暴露评估。在国际上首先建立了反映人体微量氯丙醇暴露的8—氯乳酸的痕量检测技术，并作为理想的接触标志物用于人体氯丙醇的暴露评价；初步建立了以监测母乳中二噁英负荷水平作为接触标志物和生殖内分泌指标作为效应标志物的体系；应用人胚肾LH／CG受体重组细胞株生物发光法测定血清中的BCG。研制出监测网研制数据上报系统计算机软件。该研究对保障食品安全提供了方法和科学依据。     

机械化生产黄酒酵母菌生物学特性的研究

机械化生产黄酒（半甜型、半干型、干型）的发酵过程是糖化和以多品种、高密度的酵母与乳酸杆菌（细菌）协同作用的混合发酵过程（即：边糖化、边酵母发酵、边乳酸杆菌或细菌发酵同时进行的三边发酵）。基于“三边发酵”理论中对机械化生产黄酒对酵母菌生物学特性的要求,研究了黄酒酵母菌的生物学特性,筛选出了适宜黄酒机械化生产用的优良酵母菌株。     

The effect of pH,sodium chloride,sucrose, sorbate and benzoate on the growth of food spoilage yeasts

The effects of pH, concentration of NaCl, concentration of sucrose and concentrations of sorbic and benzoic acids on growth were examined for 30 strains of food spoilage yeasts, representingDebaryomyces hansenii, Yarrowia lipolytica, Kloeckera apiculata, Zygosaccharomyces bailii, Zygosaccharomyces rouxii, Kluyveromyces marxianus, Pichia membranaefaciens, Pichia anomalaandSaccharomyces cerevisiae.Zygosaccharomyces bailiidid not grow at pH 7.0 andZ. rouxii, Kl. apiculataandP. membranaefaciensdid not grow at pH 8.0. OnlyKl. apiculatagrew at pH 1.5–2.0. The remaining species grew at pH 2.5–8.0. None of the species grew at 20% NaCl but strains ofD. hansenii, Z. rouxiiandP. anomalagrew at 15% NaCl.S. cerevisiaeandK. marxianuswere the least salt tolerant, showing no growth at 7.5% NaCl and 10% NaCl, respectively. Medium pH influenced growth in the presence of NaCl. ForY. lipolytica, D. hanseniiandS. cerevisiae, greatest tolerance of NaCl occurred at pH 5.0–7.0, but forKl.apiculata, D. membranaefaciensandZ. bailiibest tolerance occurred at pH 3.0.K. apiculatagrew in the presence of 12.5% NaCl at pH 2.0. All yeasts grew at 50% sucrose, withZ. rouxii, Z. bailiiandP. anomalaandD. hanseniigrowing at 60–70% sucrose. Medium pH in the range 2.0–7.0 had little effect on ability to grow in the presence of high sucrose concentrations.Z. bailiiandY. lipolyticawere the species most tolerant of sorbate and benzoate preservatives (750–1200 mg l⁻¹) at pH 5.0.     

RIDASCREEN® FAST PEANUT, a rapid and safe tool to determine peanut contamination in food

During the last years allergenic substances in food have gained more and more attention. Stricter rules for a peanut free food labelling demand a peanut contamination less than 5 ppm. The maintenance of a high quality of food products with regards to allergenic exposure is preferable warranted with rapid tests that can be utilized as an aid for suppliers to control raw materials, to avoid cross contamination during production and to check the final products. A rapid sandwich peanut ELISA was developed, which covers a measuring range of 2.5–20 ppm peanut (detection limit of 1.5 ppm). This test was successfully evaluated in an independent study under the supervision of the AOAC Research Institute, getting the AOAC certificate No. 030404. In‐house validation and independent validation data demonstrate the reliability, accuracy and precision of the test.     

Molecular taxonomy of the yeasts

The term ‘yeast’ is often taken as a synonym for Saccharomyces cerevisiae, but the phylogenetic diversity of yeasts is illustrated by their assignment to two taxonomic classes of fungi, the ascomycetes and the basidiomycetes. Subdivision of taxa within their respective classes is usually made from comparisons of morphological and physiological features whose genetic basis is often unknown. Application of molecular comparisons to questions in yeast classification offers an unprecedented opportunity to re-evaluate current taxonomic schemes from the perspective of quantitative genetic differences. This review examines the impact of molecular comparisons, notably rRNA/rDNA sequence divergence, on the current phenotypically defined classification of yeasts. Principal findings include: 1) budding ascomycetous yeasts are monophyletic and represent a sister group to the filamentous ascomycetes, 2) fission yeasts are ancestral to budding and filamentous ascomycetes, 3) the molecular phylogeny of basidiomycetous yeasts is generally congruent with type of hyphal septum, presence or absence of teliospores in the sexual state, and occurrence of cellular xylose.     

Patulin contamination in fruit derivatives,including baby food,from the Spanish market

The aim of this study was to provide a current overview on patulin (PAT) contamination of apple products in Spain. A second aim was to provide some data on the effect of processing stages of fruit juice concentrates on patulin levels. None of the analysed samples contained PAT concentrations exceeding the maximum levels fixed by the EU. Pear and apple concentrates showed the highest levels (up to 126 μg/kg). After milling, patulin levels did not exhibit important differences, except for at the concentration stage where a greater than fourfold mean increase was recorded. Moreover, a decrease was observed in those fruit juices that were decolourised after ultrafiltration. Thus, patulin presence in fruit products might not pose a health risk for the average consumer, although studies on patulin intake by populations consuming high amounts of fruit derivatives might be of importance.