Influence of storage temperature on microbial spoilage characteristics of haddock fillets (Melanogrammus aeglefinus) evaluated by multivariate quality prediction

The proliferation of specific spoilage organisms (SSO) and quality changes were evaluated in haddock fillets stored in styrofoam boxes at 0, 7 and 15 degrees C and under temperature fluctuations. A rapid electronic nose technique was used to monitor different classes of compounds, representing microbial metabolites that were characteristic for the onset of spoilage odors. Photobacterium phosphoreum predominated among the spoilage bacteria and high levels of TVB-N were observed at sensory rejection. Pseudomonas spp. appeared to be responsible for the development of sweet, fruity spoilage odors in haddock fillets coinciding with increasing response of the electronic nose CO sensor. H(2)S-producing bacteria, most likely Shewanella putrefaciens, were associated with the H(2)S sensor's response at abusive temperature conditions. Partial Least Squares Regression (PLSR) was used as an explorative tool to provide a better understanding of the spoilage potential of SSOs, by evaluating models based on electronic nose responses and counts of specific spoilage organisms to predict sensory quality (Torry scores). The best prediction of the sensory quality was obtained by PLSR models based on five variables: the electronic nose sensors (CO, NH(3) and H(2)S), pseudomonads counts and a time-temperature variable. Good agreement between the predicted and experimental data indicates that these variables characterize the sensory quality of haddock fillets stored under different temperatures.     

Discrimination of Chicken Seasonings and Beef Seasonings Using Electronic Nose and Sensory Evaluation

This study examines the feasibility of electronic nose as a method to discriminate chicken and beef seasonings and to predict sensory attributes. Sensory evaluation showed that 8 chicken seasonings and 4 beef seasonings could be well discriminated and classified based on 8 sensory attributes. The sensory attributes including chicken/beef, gamey, garlic, spicy, onion, soy sauce, retention, and overall aroma intensity were generated by a trained evaluation panel. Principal component analysis (PCA), discriminant factor analysis (DFA), and cluster analysis (CA) combined with electronic nose were used to discriminate seasoning samples based on the difference of the sensor response signals of chicken and beef seasonings. The correlation between sensory attributes and electronic nose sensors signal was established using partial least squares regression (PLSR) method. The results showed that the seasoning samples were all correctly classified by the electronic nose combined with PCA, DFA, and CA. The electronic nose gave good prediction results for all the sensory attributes with correlation coefficient (r) higher than 0.8. The work indicated that electronic nose is an effective method for discriminating different seasonings and predicting sensory attributes.     

电子鼻应用于猪肉丸子香味预测

为应用电子鼻技术快速、客观地评价猪肉丸子风味,实验设计了4?种肥肉、瘦肉配比（100%瘦、90%瘦、80%瘦和70%瘦）的猪肉丸子,使用电子鼻和顶空固相微萃取和气相色谱-质谱（gas chromatography-mass spectrometry,GC-MS）联用对猪肉丸子的各种挥发性物质进行检测。同时对其进行香味指标感官评定。采用线性判别和神经网络方法对不同猪肉丸子的电子鼻数据进行识别分类;并利用偏最小二乘回归方法对电子鼻传感器和挥发性物质的相关性进行分析。结果表明,4?类丸子在香味评价上差异极显著（P＜0.01）,肥肉比例高的丸子获得了较高的评分。线性判别分析和神经网络方法的分类效果显示,电子鼻对4?类猪肉丸子具有良好的分类能力。GC-MS共检测出了67?种风味化合物,其中主要是醛类、醇类、酮类等物质,挥发性风味物质的差异是造成各类丸子感官评分差异的根本原因。偏最小二乘回归模型显示电子鼻传感器数据与主要挥发性化合物相对含量具有良好的相关性。使用逐步回归建立电子鼻与评价指标数据之间的分值预测回归模型（R2＞0.9,P＜0.01）,表明丸子香味可以使用电子鼻进行预测。     

鮰鱼冷藏过程中气味和新鲜度的变化及相关性

以真空包装与空气包装鮰鱼为研究对象,采用固相微萃取-气相色谱-质谱联用结合电子鼻技术,对鮰鱼4℃冷藏过程中的挥发性成分进行分析,并对不同样品的电子鼻传感器信号进行分析,同时结合感官评分、K值、三甲胺含量、挥发性成分及电子鼻传感器信号进行相关性分析。结果表明：鮰鱼4 ℃冷藏过程中的特征风味物质主要为己醛、壬醛、苯甲醛和1-辛烯-3-醇;电子鼻可以区分不同冷藏时间、不同包装的鮰鱼;感官评定结果表明,鮰鱼冷藏4～5 d时开始腐败,且真空包装组较空气包装组变化缓慢;冷藏鮰鱼三甲胺含量和K值随冷藏时间延长而逐渐上升,真空包装样品新鲜度较空气包装组好;相关性及主成分分析结果表明,苯甲醛、1-辛烯-3-醇可作为表征鮰鱼腐败的挥发性化合物。     

Monitoring sausage fermentation using an electronic nose

In this study a sensor array and pattern recognition routines (an electronic nose) were used to monitor a sausage fermentation in order to follow the changes in emitted volatile compounds during the fermentation process and to compare the electronic nose results with a sensory analysis. From the sensor array responses the fermentation time could be predicted using different methods, where principal component regression and an artificial neural network based on all sensors in the electronic nose performed best. A sensory panel evaluated the final product and these results were compared with the electronic nose measurements in the early stage of the process and on the final sausages. A principal component analysis showed that one of the sausage batches clearly deviated from the other using both the sensory panel data and the electronic nose responses. The deviating batch was different already after 4 h and the difference was consistent during the process. © 1998 SCI.     

The effective product life of vacuum-packaged beef imported into Saudi Arabia by sea, as assessed by chemical, microbiological and organoleptic criteria

Five transport and storage trials were conducted on commercial shipments of vacuum-packaged beef half striploins imported into Saudi Arabia by sea from Australia, New Zealand and the Republic of Ireland. The cold chains, from packaging to the end of chilled storage in Saudi Arabia, were monitored using miniature electronic data loggers placed in cartons of striploins. Development of spoilage microfloras was followed from packaging to trial end using a differential aerobic plate count technique. Changes in meat pH, total volatile nitrogen (TVN) and free fatty acid (FFA) content were determined over the storage period. Sensory evaluations to identify spoilage conditions and to determine consumer acceptability were also conducted over the course of storage in Saudi Arabia. Results indicated that aerobic plate counts, TVN and FFA were all unsuitable as indicators of the fitness, or acceptability of vacuum-packaged beef for human consumption. Under good but commercially realistic conditions (i.e. normal ultimate pH beef, initial microbial contamination at packaging of less than 10³/cm², packaging, film oxygen transmission rate less than 40 ml/m²/24 h/atm at 23°C and 90% R.H., and mean product temperature during transport and storage of 0°C), vacuum-packaged beef transported by sea has an anticipated product life of at least 90 days measured from the date of slaughter. Under the conditions just stated, deterioration of meat texture resulting from excessive aging rather than the onset of overt microbial spoilage will limit the effective product life of vacuum-packaged beef.     

内源化学反应及细菌活动对冰温贮藏罗非鱼片腐败变质的贡献研究

目的 评估内源化学反应及细菌活动对冰温贮藏罗非鱼片腐败变质的贡献。方法 研究经抑菌处理及未经抑菌处理的罗非鱼片在冰温贮藏期间的菌落总数、挥发性盐基氮(totalvolatilebasicnitrogen,TVB-N)值、pH、硫代巴比妥酸(thiobarbituric acid, TBA)值及感官鲜度的变化,采用电子鼻监测挥发性成分的变化,并对未经抑菌处理罗非鱼片各指标与菌落总数间进行皮尔逊相关性分析。结果 贮藏期间经抑菌处理的样品的菌落总数始终小于5.05 log CFU/g, TVB-N值小于3.00 mg/100 g, pH及电子鼻测定的各种挥发性成分基本未变,未发生感官腐败,虽然TBA值有所增加(P<0.05),但始终低于0.05 mg MDA/100 g。而未经抑菌处理的罗非鱼片,菌落总数在21 d时达到9.19 log CFU/g, TVB-N值增至40.69 mg/100 g, pH由6.65增至7.63,电子鼻测定的氮氧化合物、硫化物及有机硫化物骤增, TBA值增至0.072 mg MDA/100 g,显著高于抑菌处理的样品,感官腐败明显。结论 冰温贮藏条件下内源...     

Sensory based quality control utilising an electronic nose and GC-MS analyses to predict end-product quality from raw materials

The objective of the present study was to investigate if an electronic nose, comprising six metal oxide sensors (MOS) could predict the sensory quality of porcine meat loaf, based on measuring the volatiles in either the raw materials or the meat loaf produced from those raw materials. A multivariate data analysis strategy involving analysis of variance partial least squares regression (APLSR) and principal component analysis (PCA) was used to determine causal and predictive relationships between the raw material and meat loaf samples, sensory analysis, electronic nose, and GC-MS measurements. The results showed that the six MOS sensors in the Danish odour sensor system (DOSS) could detect the raw materials that led to unacceptable products, as determined by sensory profiling and in-house sensory quality control (QC), and separate those raw materials from each other, based on the volatile composition, as determined by GC-MS. However, the electronic nose was unable to detect all the sensory unacceptable meat loaf samples themselves due to changes in the volatile composition after cooking. Analysis of the GC-MS compounds identified from raw materials and meat loaf samples indicate that two MOS sensors mainly responded to alcohols and to a lesser degree to aldehydes and alkanes, whereas two other sensors most likely responded to low molecular weight sulphur compounds. Thus, the results indicate that measuring volatiles with the MOS sensors in the DOSS system, on raw materials for processed meat products, may be a feasible strategy in sensory based quality control, and may also have potential in predicting the sensory quality of the end product.     

冷鲜牛肉贮藏中菌群结构及优势菌致腐性的分析

为探究牛肉在0?℃冷藏下微生物菌群变化和优势腐败菌,采用培养依赖的16S rRNA结合高通量测序技术分析牛肉样品的微生物多样性变化。通过定期测定接种牛肉汁的生长、感官、蛋白酶活性、pH值和挥发性盐基氮（total volatile basic nitrogen,TVB-N）值,分析分离株的致腐特征。结果表明,牛肉冷藏中感官品质保持良好,15?d出现异味,18?d有腐臭味。而样品中菌落总数第3天快速上升,15?d菌落总数为8.73（lg（CFU/g））,之后呈现稳定,假单胞菌（Pseudomonas spp.）、热死环丝菌（Brochothrix thermosphacta）、肠杆菌（Enterobacter）和乳酸菌4 种分离培养基中细菌与菌落总数增长趋势相似,其中假单胞菌增长最快,肠杆菌数和乳酸菌数生长最慢。两种菌群鉴定结果显示,冷鲜牛肉初始微生物构成复杂,包括热死环丝菌、不动杆菌属（Acinetobacter spp.）、气单胞菌属（Aeromonas spp.）和假单胞菌等多种菌属构成,而腐败末期菌群构成趋于单一,假单胞菌和热死环丝菌为优势腐败菌,特别是莓实假单胞菌（P. fragi）。将腐败分离株10?株假单胞菌、4?株热死环丝菌和1?株蜂房哈夫尼菌（Hafnia alve）接种于冷藏的牛肉汁,发现假单胞菌和蜂房哈夫尼菌的接种组感官评分、pH值和TVB-N值高于热死环丝菌,且假单胞菌有较强的蛋白酶活性。研究表明,结合感官和微生物评价冷鲜牛肉贮藏期为15?d,且菌群多样性下降,假单胞菌和热死环丝菌是优势腐败菌,其中假单胞菌致腐性较强。     

微发酵对牛肉干风味的影响

为改善和丰富市场上牛肉干的口味,以未加发酵剂制作的牛肉干为空白组,通过电子感官仪器、气相色谱-嗅闻-质谱联用仪、氨基酸分析仪和感官评价研究微发酵对牛肉干风味的影响。结果表明,微发酵对牛肉干的风味影响较大。电子感官仪器可以很好区分2 组样品,说明微发酵可以改善产品的风味。与空白组相比,微发酵可以显著提高产品的挥发性风味物质和游离氨基酸含量,说明微发酵可以促进产品滋味和气味物质的形成。通过火山图分析,结合相对气味活度值、嗅闻检测和味觉分析系统分析结果,得到微发酵牛肉干的特征性滋味物质为谷氨酸,特征性气味物质为3-甲基丁醇、己醛、辛醛、壬醛、反式-2-癸烯醛、反,反-2,4-癸二烯醛和3-甲基丁酸,为后续牛肉干的风味调控提供一定的理论基础和技术支持。     

冷水浸泡和沸水漂烫预处理对牛肉挥发性成分的影响

采用电子鼻技术、同时蒸馏萃取和气相色谱-质谱（gas chromatography-mass spectrometry,GC-MS）法研 究2 种预处理方式（冷水浸泡2 h和沸水漂烫40 s）对牛肉挥发性风味成分的影响。电子鼻分析结果表明,2 种预处 理方式牛肉的气味有明显差异。GC-MS测定结果表明：冷水浸泡2 h和沸水漂烫40 s的牛肉中分别鉴定出35、39 种 挥发性成分,2 种预处理方式牛肉中共鉴定出48 种挥发性成分,其中共有成分26 种,且2 种预处理方式牛肉中的挥 发性成分种类和含量有较大差异。冷水浸泡能更多地保留牛肉风味物质中的醛类物质,使牛肉的脂香味浓郁,香味 成分更丰富,因此预处理温度是造成牛肉风味差异的主要因素。     

Volatiles for mycological quality grading of barley grains: determinations using gas chromatography-mass spectrometry and electronic nose

The possibility of using an electronic nose or gas chromatography combined with mass spectrometry (GC-MS) to quantify ergosterol and colony forming units (CFU) of naturally contaminated barley samples was investigated. Each sample was split into three parts for (i) ergosterol and CFU analysis, (ii) measurements with the electronic nose and (iii) identification of volatiles collected on an adsorbent with a GC-MS system. Forty samples were selected after sensory analysis to obtain 10 samples with normal odour and 30 with some degree of off-odour. The data set of volatile compounds and the data collected from the electronic nose were evaluated by multivariate analyse techniques. SIMCA classification (soft independent modelling of class analogy) was used for objective evaluation of the usefulness of the data from the GC-MS or electronic nose measurements for classification of grain samples as normal or with off-odour. The main volatile compounds of grain with normal odour were 2-hexenal, benzaldehyde and nonanal, while 3-octanone, methylheptanone and trimethylbenzene were the main volatile compounds of grain with off-odours. Using data from the electronic nose three samples of 40 were misclassified, while data analysis of the volatile compounds detected with the GC-MS, led to six misclassified samples. Regression models (partial least-squares, PLS) were built to predict ergosterol- and CFU-levels with data from the GC-MS or electronic nose measurements. PLS models based on both GC-MS and electronic nose data could be used to predict the ergosterol levels with high accuracy and with low root mean square error of prediction (RMSEP). CFU values from naturally infected grain could not be predicted with the same degree of confidence.     

电子鼻检测不同贮藏温度下猪肉新鲜度变化

采用电子鼻研究冷却猪肉在不同贮藏温度(－ 18、0、4、10、20℃)条件下新鲜度变化规律。选用优化后的进样体积(1500μL)进样,对实验数据进行主成分分析(PCA)、货架期模拟及拟合感官评分的偏最小二乘回归分析(PLS)。结果表明：5 种温度条件下贮藏不同时间肉样挥发性气味差异显著,贮藏温度越高肉样新鲜度发生显著下降时刻越早,预测时间分别为336、180、72、48、18h。对4、20℃条件下电子鼻检测数据与感官评分拟合后进行PLS 分析,相关系数分别高达0.9982和0.9998,表明电子鼻能代替感官评定。逐一选取每一根传感器进行PLS 拟合后发现,TA/2、T40/1、T40/2、P30/2、P40/1、P10/2、P10/1 是对不同新鲜度肉样挥发性气味具有良好特异性响应的传感器。     

气相色谱-质谱联用和电子鼻用于鉴别鸡精调味品香气成分

以新鲜鸡精、久置鸡精和哈败鸡精为研究对象,采用顶空固相微萃取-气相色谱-质谱联用技术分析其挥发性风味成分,并利用感官评价和电子鼻技术对鸡精样品的风味属性进行评定,并采用主成分分析法和聚类分析法研究电子鼻对鸡精的区分能力,采用偏最小二乘法建立挥发性风味成分与嗅闻感官属性之间的相关性。结果表明,鸡精调味品共检测出53种挥发性风味成分,主要包括烯类3种、醇类6种、酮类4种、醛类12种、酯类6种、芳香族化合物3种、含硫化合物13种、杂环化合物4种和其他化合物2种;人工感官评价和电子鼻结果一致,认为新鲜鸡精与久置鸡精的风味更为接近,与挥发性风味物质含量结果相吻合;偏最小二乘法结果表明,有30种挥发性风味成分与嗅闻感官属性具有较好的相关性。研究结果表明气相色谱-质谱、电子鼻结合化学计量学方法可以综合评价鸡精调味品的嗅觉风味。     

不同水解度鸡肉香精的风味研究

以5种不同水解度的鸡骨架水解液为基料,通过美拉德反应制备鸡肉香精。利用感官评价以及电子鼻技术对不同水解度鸡肉香精的风味属性进行评价,并用气相色谱质谱仪(GC-MS)技术分析检测其风味物质。采用主成分分析(PCA)区分不同水解度鸡肉香精,通过偏最小二乘法(PLSR)将感官属性与GC-MS检测得到的风味物质进行相关性分析。感官评定结果表明5种不同水解度鸡肉香精的鸡肉味、脂肪香、大蒜味、辛辣味、酱香味、协调性,整体风味具有显著差异;电子鼻结合PCA分析不同水解度鸡肉香精达到99%的区分度,可以很好的区分辨别不同水解度鸡肉香精;GC-MS分析检测不同水解度鸡肉香精得到82种风味物质,主要包括醛类(17),酮类(7),含氮含硫化合物(12),烯类(15),醇类(19),酯类(2)以及酸类(10)。PLSR分析得到36种风味物质与感官属性相关性较好。实验说明电子鼻,GC-MS结合多元统计分析方法是一项有效的识别不同水解度鸡肉香精的工具。     

基于电子鼻技术判定冷鲜罗非鱼片品质劣变进程

应用电子鼻采集贮藏过程冷鲜罗非鱼片顶空挥发性气味,同步进行感官评价、微生物和理化分析。结果表明：传感器响应信号随着鱼片气味浓度增大而增大,且对不同新鲜度气味有良好响应。线性判别(LDA)比主成分分析(PCA)更能有效区分鱼片的不同新鲜度、微生物及挥发性盐基氮含量,表明电子鼻可快速检测鱼片的品质劣变进程。通过负荷加载分析和相关分析表明,W2W、W1W、W1S、W2S对区分冷鲜罗非鱼片不同新鲜度的贡献较大,并与感官可接受性、菌落总数和挥发性盐基氮的相关性良好,可作为今后研制鱼用电子鼻系统精选传感器的理论参考。     

Sensory and microbiological quality assessment of beef fillets using a portable electronic nose in tandem with support vector machine analysis

The performance of a portable quartz microbalance based electronic nose has been evaluated in monitoring aerobically packaged beef fillet spoilage at different storage temperatures (0, 4, 8, 12, and 16 °C). Electronic nose data were collected from the headspace of meat samples in parallel with data from microbiological analysis for the enumeration of the population dynamics of total viable counts, Pseudomonas spp., Brochothrix thermosphacta, lactic acid bacteria and Enterobacteriaceae. Qualitative interpretation of electronic nose data was based on sensory evaluation discriminating samples in three quality classes (fresh, semi-fresh, and spoiled). Support Vector Machine (SVM) classification and regression models using radial basis kernel function were developed to classify beef fillet samples in the respective quality class, and correlate the population dynamics of the microbial association with electronic nose sensor responses. The obtained results demonstrated good performance in discriminating meat samples in one of the three pre-defined quality classes. Overall classification accuracies of prediction above 89% were obtained for the three sensory classes regardless of storage temperature. For SVM regression model development, correlations above 0.96 and 0.86 were obtained between observed and predicted microbial counts for the training and test data sets, respectively.     

Radiation preservation of vacuum-packaged sliced corned beef

Luncheon meats are cooked meat products which are commonly sold sliced and vacuum-packaged. They are recontaminated during slicing and packing and as a result may have a starting count as high as 10⁴–10⁵ bacteria per g. Since the surface-to-volume ratio is comparatively high, bacterial spoilage may occur after only 2–3 weeks at 5° C. Treatment of vacuum-packaged sliced corned beef with radiation doses of about 1, 2 and 4 kGy reduced the initial microbial count by about 1, 2.5 and 5 log₁₀ units respectively. The treatments caused changes in the aroma and flavour of the meat and these were evaluated using a trained taste panel. Changes in aroma and flavour caused by doses of 2 and 4 kGy were significant but were rated by the panel as only slight and slight-moderate respectively. Meat treated with a dose of 2 kGy had a storage life of about 5 weeks at 5° C. Treatment with a 4 kGy dose further delayed the onset of spoilage caused by bacterial growth, Irradiation caused a change in the nature of the microbial flora present at spoilage. The normal Gram-positive flora of non-irradiated meat was replaced by a mixed flora of Gram-negative and Gram-positive bacteria following a dose of 2 kGy. Slow-growing Gram-negative rods were dominant after a dose of 4 kGy.     

Aroma features of honey measured by sensory evaluation,gas chromatography-mass spectrometry,and electronic nose

To study the aroma features of different varieties of honey, five honey samples from different botanical origins were characterized by sensory evaluation, gas chromatography-mass spectrometry and electronic nose analysis. The sensory evaluation results gave a good reflection of the honey’s different aroma characteristics. A total of 55 volatile compounds were identified by headspace solid-phase micro-extraction followed by gas chromatography-mass spectrometry, and among these compounds, 13 were found in all of the honey samples. A number of differences were observed in the composition of volatile components from the five types of honey. Twenty-two compounds were selected as typical odor-active compounds which co-varied well with the five sensory attributes by partial least squares regression. The correlation results between the sensory profiles and electronic nose data showed that the electronic nose could give comparable results in predicting the sensory attributes of honey. In conclusion, the combination of sensory evaluation, gas chromatography-mass spectrometry analysis of volatile compounds, and electronic nose data with partial least squares regression analysis could be applicable for the overall analysis of aroma features for honey.     

基于电子鼻的红肠风味评价

为应用电子鼻快速、客观地评价红肠风味,使用电子鼻以及顶空固相微萃取和气相色谱-质谱联用对3 个不同生产批次的各批次3 种不同红肠中挥发性物质进行检测分析,并对其进行感官指标评定。采用支持向量机方法对不同红肠样品的电子鼻数据进行识别分类;利用相对气味活度值确定不同红肠中的关键风味物质;用主成分分析方法对红肠挥发性物质整体分析;利用正交偏最小二乘判别分析方法对电子鼻传感器和红肠关键风味的相关性进行分析,并使用逐步回归建立电子鼻与关键风味物质和感官评价指标数据的回归模型。通过支持向量机分析结果可知,电子鼻对不同种类红肠以及不同生产批次同种类红肠均具有良好的区别能力;气相色谱-质谱联用检测出不同种类化合物共117 种;通过相对气味活度值可知不同红肠中的关键风味物质种类差异较大,仅烯丙硫醇是各红肠的共有关键风味物质;主成分分析表明不同种类红肠在总体风味成分上明显不同;感官分析表明不同红肠在不同口感风味评价上存在差异,烟熏味和咸味为红肠最主要的风味;正交偏最小二乘判别分析显示电子鼻传感器数据与关键风味物质具有良好的相关性;建立电子鼻与关键风味物质和感官评价指标回归模型（R2＞0.8,P＜0.01）表明应用电子鼻可以对红肠风味进行评价预测分析。