食源性腐败菌挥发性有机化合物的研究进展

食源性腐败菌是食品腐败的重要原因, 它可通过初级或次级代谢产生具有异味的挥发性有机化合物(volatile organic compounds, VOCs), 加速食品的腐败进程。腐败菌种类及组成会随食品基质和贮藏条件而改变, 导致产生的VOCs也具有多样性和差异性。随挥发性有机物质收集和检测技术的快速发展, 通过分析腐败菌相关的VOCs成分组成可鉴别食源性腐败菌种类和食物腐败进程。本文对常见腐败菌VOCs的产生途径和种类进行归纳, 并重点探讨了VOCs提取分析技术及在食品腐败研究中的具体应用, 为有效进行腐败菌防控, 提升食品质量和安全提供参考。     

凡纳滨对虾优势腐败菌鉴定及其致腐能力的初步研究

分析鉴定了凡纳滨对虾0℃与20℃贮藏条件下的菌相组成与优势腐败菌,并对优势腐败菌16SrDNA、生长动力学、致腐能力与菌落数的变化进行了测定。结果表明,0℃与20℃贮藏条件下,对虾优势腐败菌分别是希瓦氏菌(30%)、不动杆菌(16.7%)与希瓦氏菌(46.5%)、发光杆菌(17.7%)。7℃条件下,将一定浓度的希瓦氏菌与不动杆菌菌悬液接种到无菌对虾上,结果显示接种希瓦氏菌的样品其腐败代谢产物产量因子YTVB-N/CFU、YTMA/CFU分别为12.44×10-9、6.193×10-10,而接种不动杆菌的样品其YTVB-N/CFU、YTMA/CFU分别为8.937×10-9、5.548×10-10。结果表明,7℃条件下,希瓦氏菌的致腐能力强于不动杆菌,希瓦氏菌在对虾腐败过程中占主导作用,其分析结果与对虾菌相组成的鉴定结果相一致。     

Sensory characteristics of spoilage and volatile compounds associated with bacteria isolated from cooked and peeled tropical shrimps using SPME-GC-MS analysis

The spoilage potential of six bacterial species isolated from cooked and peeled tropical shrimps (Brochothrix thermosphacta, Serratia liquefaciens-like, Carnobacterium maltaromaticum, Carnobacterium divergens, Carnobacterium alterfunditum-like and Vagococcus penaei sp. nov.) was evaluated. The bacteria were inoculated into shrimps, packaged in a modified atmosphere and stored for 27 days at 8 °C. Twice a week, microbial growth, as well as chemical and sensory changes, were monitored during the storage period. The bacteria mainly involved in shrimp spoilage were B. thermosphacta, S. liquefaciens-like and C. maltaromaticum whose main characteristic odours were cheese-sour, cabbage-amine and cheese-sour-butter, respectively. The volatile fraction of the inoculated shrimp samples was analysed by solid-phase microextraction (SPME) and gas chromatography coupled to mass spectrometry (GC-MS). This method showed that the characteristic odours were most likely induced by the production of volatile compounds such as 3-methyl-1-butanal, 2,3-butanedione, 2-methyl-1-butanal, 2,3-heptanedione and trimethylamine.     

冷却猪肉中优势腐败菌致腐能力研究

为明确冷却猪肉中优势腐败菌对其腐败的作用程度,本研究监测冷却猪肉冷藏过程中菌落总数和优势腐败菌的变化情况,并接种假单胞菌、气单胞菌、肠杆菌和热杀索丝菌于冷却猪肉中,分组检测尸胺含量在冷却猪肉冷藏过程中的变化。实验表明,优势腐败菌在冷却猪肉冷藏第5d后显著上升(p<0.05),与尸胺含量变化趋势相似,同时接种多种腐败菌与尸胺含量极显著相关(p<0.01),表明优势腐败菌的协同效应对冷却猪肉腐败具有重要作用。     

不同年份不同质量等级李渡白酒香气成分分析

目的 分析比较不同年份不同质量等级李渡白酒的香气成分差异。方法 通过感官评价、直接进样、顶空萃取和顶空固相微萃取结合气相色谱-质谱联用仪、气相色谱-离子迁移谱以及气相色谱-嗅闻-质谱联用仪分析了17个李渡酒中的香气成分,通过计算香气活性值(OAV)确定重要香气活性化合物,结合偏最小二乘法分析得到差异香气物质。结果 共鉴定出李渡酒中的92种挥发性化合物,26种香气活性化合物;浓度最高的化合物是乳酸乙酯(2538.18 mg/L);己酸乙酯(OAV: 876~220920)等8种化合物香气贡献较大,酯类化合物的贡献最大,一级、二级、优级的李渡酒三年、五年的重要香气化合物香气强度更强,含量更高;且己酸乙酯等6种化合物、苯乙醇等18种化合物分别是导致不同年份、不同质量等级酒样产生差异的重要物质。结论 本研究分析鉴定了17个李渡酒样的香气物质,找到了导致不同年份不同质量等级酒样之间香气差异的化合物,为李渡酒的风味调控提供了参考数据。     

Predication of Japanese green tea (Sen-cha) ranking by volatile profiling using gas chromatography mass spectrometry and multivariate analysis

The sensory quality ranking of Japanese green tea (Sen-cha) was evaluated and predicted using volatile profiling and multivariate data analyses. The volatile constituents were extracted from tea infusion using vacuum hydrodistillation and analyzed using GC/MS. A quality of green tea could be discriminated to a high or low grade regarding the volatile profile by partial least squares discriminant analysis (PLS–DA). A quality ranking predictive model was developed from the relationship between subjective attributes (sensory quality ranking) and objective attributes (volatile profile) using partial least squares projections to latent structures together with the preprocessing filtering technique, orthogonal signal correction (OSC). Several volatile compounds highly contributed to model prediction were identified as various odor-active compounds, including geraniol, indole, linalool, cis-jasmone, dihydroactinidiolide, 6-chloroindole, methyl jasmonate, coumarin, trans-geranylacetone, linalool oxides, 5,6-epoxy-β-ionone, phytol, and phenylethyl alcohol. The whole fingerprints of these volatile compounds could be possible markers for the overall quality evaluation of green tea beverage.     

A comparison of artificial neural networks and partial least squares modelling for the rapid detection of the microbial spoilage of beef fillets based on Fourier transform infrared spectral fingerprints

A series of partial least squares (PLS) models were employed to correlate spectral data from FTIR analysis with beef fillet spoilage during aerobic storage at different temperatures (0, 5, 10, 15, and 20 °C) using the dataset presented by Argyri et al. (2010). The performance of the PLS models was compared with a three-layer feed-forward artificial neural network (ANN) developed using the same dataset. FTIR spectra were collected from the surface of meat samples in parallel with microbiological analyses to enumerate total viable counts. Sensory evaluation was based on a three-point hedonic scale classifying meat samples as fresh, semi-fresh, and spoiled. The purpose of the modelling approach employed in this work was to classify beef samples in the respective quality class as well as to predict their total viable counts directly from FTIR spectra. The results obtained demonstrated that both approaches showed good performance in discriminating meat samples in one of the three predefined sensory classes. The PLS classification models showed performances ranging from 72.0 to 98.2% using the training dataset, and from 63.1 to 94.7% using independent testing dataset. The ANN classification model performed equally well in discriminating meat samples, with correct classification rates from 98.2 to 100% and 63.1 to 73.7% in the train and test sessions, respectively. PLS and ANN approaches were also applied to create models for the prediction of microbial counts. The performance of these was based on graphical plots and statistical indices (bias factor, accuracy factor, root mean square error). Furthermore, results demonstrated reasonably good correlation of total viable counts on meat surface with FTIR spectral data with PLS models presenting better performance indices compared to ANN.     

Pedot modified electrodes in amperometric sensing for analysis of red wine samples

A poly(3,4-ethylendioxythiophene) modified electrode has been considered as a potentially useful amperometric sensor to use either alone or in the frame of a set of sensors bearing complementary information, i.e. within an electronic tongue. The sensor is proposed in blind analysis of red wines, for classification and calibration purposes. The data obtained from voltammetric measurements have been treated using partial least squares analysis. A calibration procedure has been performed to correlate results from analyses of wines, executed with traditional analytical methods, with the corresponding voltammetric responses. Moreover, classification models of the wine samples, based on quantitative parameters and qualitative information about origin and variety, have been built. The developed electrochemical sensor also allows the fast identification of samples exceeding threshold limits of meaningful parameters for quality control in the wine industry, such as SO₂, colour intensity and total polyphenols. The application of the system within a sensor array (electronic tongue) to fast pre-screening routine control procedure is proposed.     

接种不同优势腐败菌的冷藏猪肉中挥发性物质的研究

为研究接种不同优势腐败菌的新鲜猪肉在4℃冷藏中的变化,将梭状芽孢杆菌、韩国假单胞菌和热死环丝菌分别接种到新鲜猪肉上,采用顶空固相微萃取-气相色谱-质谱联用（HS-SPME-GC-MS）技术,研究其在储藏过程中产生的挥发性物质。实验显示,不同样品在48、96、144h贮藏时间下的挥发性成分有较大差异,随着冷藏时间的增加,烷烃类物质种类及含量均明显增加;醇类物质含量增加而醛类物质含量减少;硫氢甲烷、3-甲硫基丙烯等含硫化合物被检测出,但含量较低;酸类物质含量随贮藏时间的延长而逐渐增加;接种梭状芽孢杆菌的样品检测出了高含量的3-羟基-2-丁酮,接种热死环丝菌的样品出现高含量的3-甲基丁醇。结果表明,接菌样品与对照样品的挥发性物质总含量存在显著差异（p<0.05）,即上述3种菌种会对冷藏猪肉的挥发性物质总含量产生显著影响。      

Diversity and technological potential of lactic acid bacteria of wheat flours

Lactic acid bacteria (LAB) were analysed from wheat flours used in traditional bread making throughout Sicily (southern Italy). Plate counts, carried out in three different media commonly used to detect food and sourdough LAB, revealed a maximal LAB concentration of approximately 4.75 Log CFU g⁻¹. Colonies representing various morphological appearances were isolated and differentiated based on phenotypic characteristics and genetic analysis by randomly amplified polymorphic DNA (RAPD)-PCR. Fifty unique strains were identified. Analysis by 16S rRNA gene sequencing grouped the strains into 11 LAB species, which belonged to six genera: Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Pediococcus and Weissella. Weissella cibaria, Lactobacillus plantarum, Leuconostoc pseudomesenteroides and Leuconostoc citreum were the most prevalent species. The strains were not geographically related. Denaturing gradient gel electrophoresis (DGGE) analysis of total DNA of flour was used to provide a more complete understanding of the LAB population; it confirmed the presence of species identified with the culture-dependent approach, but did not reveal the presence of any additional LAB species. Finally, the technological characteristics (acidifying capacity, antimicrobial production, proteolytic activity, organic acid, and volatile organic compound generation) of the 50 LAB strains were investigated. Eleven strains were selected for future in situ applications.     

冰温贮藏中南美白对虾特定腐败菌的分离鉴定及其腐败能力分析

为了分离鉴定南美白对虾在冰温贮藏条件下的腐败菌,并分析其腐败能力的大小。通过冻结实验,确定南美白对虾的冰点,在0℃与冰点之间贮藏南美白对虾,从中分离腐败菌,进行形态学观察和分子生物学鉴定,将分离得到的腐败菌接种至灭菌虾汁中,通过产硫化氢,降解蛋白质,产挥发性盐基氮（TVB-N）的测定衡量腐败能力的大小。结果表明:从南美白对虾中分离得到12株腐败菌,分别是Shewanella hafniensis,Acinetobacter johnsonii,Planoccoccus citreus,Bacillus cereus,Acinetobacter beijerinckii,Enterobacter hormaechei,Arthrobacter bergeri,Bacillus licheniformis,未鉴定出的菌株X1和X10。在冰温贮藏条件下,导致南美白对虾腐败的优势腐败菌依次是Shewanella hafniensis、X1、Acinetobacter johnsonii和Acinetobacter beijerinckii。      

剑门火腿菌相构成及主要腐败菌特性分析

采用选择性培养基法对剑门火腿中的菌相构成进行了分析。结果表明,剑门火腿中的微生物主要为葡萄球菌、微球菌和酵母菌,其表层数量明显高于内部,乳酸菌主要分布于火腿内部,霉菌主要存在于火腿表层。剑门火腿中主要细菌的耐盐、耐酸、耐亚硝酸盐及致腐能力分析结果显示,葡萄球菌和乳酸菌的某些菌株是导致其腐败的主要微生物。     

鱿鱼丝菌相分析与腐败菌的分离鉴定

为解决提高水分含量会引起鱿鱼丝贮藏时间缩短的问题,研究了刚烘烤拉丝完水分含量为34%鱿鱼丝在贮藏过程中细菌总数、酸价、过氧化物值及菌相的消长情况。结果表明,在25℃保藏条件下,28d的细菌总数已接近国标限制上限3.0×104cfu/g,而酸价及过氧化物值变化相对较小。同时对相同工艺处理的三批鱿鱼丝在25℃保藏30d后进行菌相分离,得到两株优势腐败细菌b1和b2。经常规生理生化结合分子生物学鉴定,确定菌株b1和b2分别为肉葡萄球菌和葡萄球菌属es13菌株。     

酱油变质微生物因素及乳酸菌在防腐中的应用

酱油是经微生物发酵制成的具有独特色、香、味的液体调味品。酱油中含有充足的营养物质,并且酱油发酵体系多为混菌体系,因此在酱油发酵、生产和贮藏过程中容易因污染腐败菌出现“生花”、变馊、胀袋、沉淀、浑浊等现象,导致酱油的腐败变质。该文详细阐述了酱油中存在的腐败微生物种类和由它们引起的酱油变质现象,以及通过发酵工艺优化、添加防腐剂和生物技术等手段防止酱油腐败的相应措施。最后概述了乳酸菌的抗菌代谢产物种类与抑菌特性,并讨论了乳酸菌在酱油防腐中的应用潜力,以期为开发保障酱油品质稳定和提升的方法提供经验和参考。     

Effect of initial headspace oxygen level on growth and volatile metabolite production by the specific spoilage microorganisms of fresh-cut pineapple

The effect of initial headspace (IH) O₂ level on the shelf-life of fresh-cut pineapple was evaluated in this study. The results showed that although the IH O₂ level had a minor effect on the growth of Candida argentea, Candida sake and Meyerozyma caribbica on pineapple agar, the quantities of the volatile organic metabolites produced by these yeasts was generally smaller the lower the IH O₂ level. The only exception was the production of ethyl acetate by C. argentea, which was higher at low IH O₂ levels. In triangle tests performed with trained panellists, pineapple cubes packaged in an IH of 5% O₂ were determined to be significantly different (P < 0.05) to those packaged in 21% O₂ from day 5 of storage. Preference was shown for the pineapple cubes packaged in an IH of 5% O₂. The results imply that packaging in an IH O₂ level of 5% could be used to extend the shelf-life of fresh-cut pineapple.     

Influence of temperature on the measurement of NaCl content of aqueous solution by short-wavelength near infrared spectroscopy (SW-NIR)

Short-wavelength near infrared (SW-NIR) spectroscopy can provide a rapid and nondestructive determination of salt content in food products, and potentially monitor salt concentration of brines during processing. This is of significant importance for ensuring the safety and quality of cured and smoked foods. One of the constraints is having reliable models to predict salt concentration as temperature varies. The effect of temperature (4.0–42.9 °C) on SW-NIR spectra (594–1,105 nm) of aqueous salt solution (0–10.03% w/v) was tested in this study. A partial least squares (PLS) model based upon spectra from the entire tested temperature range, had similar predictability for salt content as PLS models developed using spectra over shorter temperature ranges (root mean square error of prediction was 0.35% versus 0.37–0.38%). The result indicated that temperature compensation with mathematical approaches for NIR spectral measurements is feasible. This could limit the cost and time necessary to collect samples over a wide range of temperature for developing and validating calibration models for salt measurement in food processing and similar applications. This research was supported by the Egtvedt Food Research Fund, USDA NRI Competitive Grants Program (NRICGP) project #2000-01617 and project #2000-01191, USDA Special Grant UAF 01-0048, the National Fisheries Institute, Eastern Oregon University, DSquared Development, Washington State University, and the City University of New York.     

市售生鲜湿面中腐败菌的分离与鉴定

采用涂布平板法从生鲜湿面中分离腐败菌,通过形态观察及分子生物学技术对分离腐败菌进行菌种鉴定。结果表明,从生鲜湿面中分离得到8株典型菌株,包括3株霉菌和5株细菌。经鉴定,3株霉菌（A1,B1,C1）分别为草酸靑霉（Penicillium oxalicum）、黄曲霉（Aspergillus flavus）、黑曲霉（Aspergillus niger）;5株细菌（S1～S5）分别为3株蜡状芽孢杆菌（Bacillus cereus）、1株肠炎沙门氏菌（Salmonella enterica）、1株副芽孢杆菌（Bacillus paramycoides）。