基于电子鼻的鲫鱼肉新鲜度研究

利用电子鼻对冷藏（4℃）和微冻（-3℃）贮藏下的鲫鱼肉挥发性气味变化进行了研究,对所获得的数据进行主成分分析（Principal Component Analysis,PCA）和判别因子分析（Discriminant Factor Analysis,DFA）,并将样品气味感官评分和电子鼻测得的数据结合,进行偏最小二乘回归分析（PLS）,建立一种基于电子鼻的判别鲫鱼新鲜度方法。结果表明:PCA和DFA分析均能将冷藏和微冻贮藏下的样品,随贮藏时间延长,挥发性气味的变化有效区分开,第一和第二主成分累计贡献率分别达到99.797%和99.425%。DF1和DF2累计贡献率达到99.263%和97.807%。气味感官评分和电子鼻数据经偏最小二乘回归分析（PLS）,相关系数（R2）达到0.9976和0.9887,存在高度的相关性。因此电子鼻可以将冷藏和微冻贮藏下,不同新鲜度的鲫鱼区分开。冷藏样品的区分效果优于微冻样品。      

Determination of the Freshness of Beef Strip Loins (M. longissimus lumborum) Using Electronic Nose

A beef strip loins (Musculus longissimus lumborum) freshness determination method utilizing electronic nose (e-nose) was investigated in this paper. Fresh beef strip loins samples were stored at 4°C continuously for 10 days. Total viable count (TVC) index, total volatile basic nitrogen (TVB-N) index, and e-nose responses to beef strip loins samples were measured every day. TVC and TVB-N index rose with the increase of storage time. Principal component analysis (PCA) only partially discriminated beef samples under different storage days. Stochastic resonance (SR) signal-to-noise ratio (SNR) spectrum discriminated all beef samples successfully. Beef strip loins freshness discrimination model was developed using SR SNR maximums (SNRmax) linear fitting regression. The proposed method forecasted beef freshness with high accuracy. It is holds promise in meat freshness determination applications.     

Nondestructive determination of salmon fillet freshness during storage at different temperatures by electronic nose system combined with radial basis function neural networks

This study develops a predictive model for determining freshness of salmon fillets during cold storage at different temperatures using electronic nose combined with principal component analysis (PCA) and radial basis function neural networks (RBFNNs). The electronic nose sensed ammonia/amines, hydrocarbons, solvents and aromatics that increased during storage. The concentrations of the volatiles were compared with the increased thiobarbituric acid (TBA), total volatile basic nitrogen (TVB-N), total aerobic bacteria count (TAC) and decreased of sensory assessments (SA). Gas chromatograph–ion mobility spectrometry analysis confirmed the changes in gas species. RBFNNs and PCA were used to establish predictive models and the relative errors of TBA, TVB-N and TAC by the PCA-RBFNNs model were all within ±10% and SA was within ±15%. These results suggest that the PCA-RBFNNs model can be used to predict changes in the freshness of salmon fillets stored at −2 to 10 °C.     

双斑东方鲀在冷藏保鲜过程中挥发性风味物质的变化

以双斑东方鲀鱼肉为研究对象,采用电子鼻及顶空固相微萃取-气相色谱-质谱（headspace solid phase microextraction-gas chromatography-mass spectrometry,HS-SPME-GC-MS）联用技术对冷藏（0 ℃和4 ℃）过程中双斑东方鲀鱼肉挥发性风味物质的种类和相对含量进行分析,探索鱼肉在冷藏过程中挥发性物质的变化规律。结果表明：双斑东方鲀在4 ℃和0 ℃条件冷藏1～3 d模糊数学感官评分较高,分别在7 d和9 d达到消费者可接受上限;电子鼻传感器响应值的主成分分析（principal component analysis,PCA）与线性判别分析能够对不同冷藏时期鱼肉中挥发性风味物质进行差异性分析,且分析结果与HS-SPME-GC-MS检测结果具有一致性。利用HS-SPME-GC-MS技术共检出48 种挥发性物质,包括烃类、醇类、醛类、酯类、芳香族化合物和含氮含硫杂环化合物,新鲜鱼肉具有鱼腥味、清新气味,冷藏11 d后,鱼肉的腥味增强,哈喇味、酸臭味加重,醛类和含氮含硫杂环化合物是导致其风味劣变的主要挥发性风味物质;结合气味活性值分析发现1-辛烯-3-醇、己醛、辛醛、壬醛和2,3-辛二酮是鱼肉在冷藏过程中的主要关键风味物质;使用PCA法构建挥发性风味物质综合评价模型为T=0.83T1＋0.15T2,评价结果与感官评价结果呈极显著负相关（P＜0.01）。由此可见电子鼻结合HS-SPME-GC-MS可用于双斑东方鲀在冷藏过程中的挥发性风味物质的区分与判别,可为研究不同冷藏时期的双斑东方鲀鱼肉风味变化提供理论参考。     

Effect of pH on TBA Values of Ground Raw Poultry Meat

Hand-deboned raw broiler meat was ground through a meat grinder and adjusted to pH values of approximately 3, 5, 7, and 9. The prepared samples along with the controls were covered and stored at 2–4°C. The 2-thiobarbituric acid (TBA) values of the samples were measured immediately after sample preparation and during refrigeration storage for a period of 14 days. The pH values affected the lipid oxidation of ground raw meat as measured by the TBA test. The lower the pH values, the stronger pro-oxidant affect. Adjusting the pH values of ground raw poultry meat to neutral or alkaline slowed the increase in TBA values.     

Application of an electronic nose for determination of pre-pressing treatment of rapeseed based on the analysis of volatile compounds contained in pressed oil

The article presents an attempt to use an electronic nose together with a new three-parameter method for generation of a digital smellprint in order to specify the mode of processing of rapeseed based on the analysis of volatile compounds contained in cold-pressed rapeseed oil. Prior to the pressing process, the seeds were roasted or improperly stored to obtain oil samples with varied technological quality. The quality of pressed oils was evaluated by determination of the acid value. Furthermore, changes in oil colour were assessed with the use of an imaging colorimeter. Volatile compounds were determined with the use of gas chromatography and an electronic nose with a metal oxide semiconductor (MOS) sensor matrix. It was found that the mode of seed pre-treatment before pressing did not change the colour of the oil significantly. However, it influenced the profile of volatile organic compounds and changed their proportions. Ketones represented the largest proportion of volatile compounds determined for roasted samples and those pressed from seeds moistened up to 25% (w.b.). Alcohols dominated in samples moistened up to 10 and 12%, terpenes were the dominant volatile compounds in samples roasted at 140 °C, and other volatile compounds dominated in samples moistened up to 10 and 20% (w.b.). In turn, esters and aromatic compounds accounted for the lowest proportion in the analysed samples. The results shown by the electronic nose were correlated with the presence of particular groups of volatile compounds in rapeseed oil.     

加热温度对南美白对虾挥发性成分的影响

采用电子鼻和固相微萃取-气相色谱-质谱（solid phase microextraction gas chromatography-massspectrometry,SPME-GC-MS）联用技术分析不同温度条件下南美白对虾虾肉的挥发性气味成分。电子鼻结果显示不同温度处理对虾肉的挥发性成分的影响较显著,35 ℃和45 ℃的挥发性成分类似但仍有差异;SPME-GC-MS分析得出,南美白对虾虾肉在35、45、60、80、95 ℃分别确定出21、24、36、43 种和49 种挥发性成分。35 ℃检测的挥发性成分可代表生虾肉,其中对风味影响较显著的有1-戊醇、1-辛烯-3-醇、壬醛等。随着温度的升高,挥发性成分中的烷烃类物质相对含量显著升高、醇类物质相对含量减少、碳原子大于10以上的饱和醛种类以及相对含量增加、芳香族化合物更加丰富。95 ℃检测出的挥发性成分可代表熟虾肉,其中对风味影响较大主要是十六醛、十八醛、二丁基羟基甲苯等。     

Nondestructive Prediction of Tilapia Fillet Freshness During Storage at Different Temperatures by Integrating an Electronic Nose and Tongue with Radial Basis Function Neural Networks

This study developed principal component analysis and radial basis function neural networks (PCA-RBFNNs) for predicting freshness in tilapia fillets stored at different temperatures by integrating an electronic nose and electronic tongue. Total volatile basic nitrogen (TVB-N), total aerobic counts (TAC), and K value increased at 0, 4, 7, and 10 °C, while sensory scores decreased significantly. The electronic nose and tongue acquired the volatiles and dissolved chemical compounds in the stored samples. Gas chromatography-mass spectrometry (GC-MS) verified the changes in gas species and contents in fillets stored for different periods of time at different temperatures. PCA-RBFNNs based on data fusion were developed and presented good performance for prediction of TVB-N, TAC, K value, and sensory score in tilapia fillets. The established PCA-RBFNNs based on feature variables of the electronic nose and tongue is a promising method to predict changes in the freshness of fillets stored from 0 to 10 °C in the cold chain.     

加热温度对花鲈鱼肉挥发性成分的影响

以花鲈鱼为研究对象,通过电子鼻和固相微萃取-气相色谱-质谱对不同温度条件下花鲈鱼肉挥发性风味成分进行鉴定,分析经过不同温度处理的花鲈鱼肉挥发性物质的种类和相对含量发生的变化,探索出花鲈鱼肉挥发性成分与加热温度的关系。结果表明:电子鼻可以较好地区分出不同温度条件下的花鲈鱼肉。主成分分析显示不同温度条件下的花鲈鱼肉气味成分有明显的差异,45℃和60℃的花鲈鱼肉的气味成分差异最小。通过气相色谱-质谱检测分析,在35、45、60、80℃和95℃的花鲈鱼肉中分别确定出25、40、52、56种和59种挥发性成分;花鲈鱼肉中所含挥发性成分的种类随着检测温度的升高而增多,醛类、酮类、醇类、烃类和芳香族类化合物的相对含量随着温度的升高发生明显变化;对花鲈鱼肉的风味形成有重要贡献的挥发性物质为己醛、壬醛、庚醛、癸醛、十一醛、2-辛烯醛、2,4-癸二烯醛、庚醇、1-辛烯-3-醇、二甲苯等化合物。     

Quality Changes of Shrimp (Pandalus borealis) Stored under Different Cooling Conditions

The influence of different cooling techniques and storage temperatures (‐1.5 °C or 1.5 °C) to prolong the shelf life of shrimp was evaluated by sensory analysis, physical methods, chemical analysis, and microbial analysis. Storage in liquid ice was more effective than flake ice or brine mixed with flake ice in delaying spoilage of the shrimp by slowing down microbial growth and formation of total volatile basic nitrogen (TVB‐N) and trimethylamine (TMA). Total viable counts (TVC) showed that bacteria grew most quickly in shrimp stored in flake ice and in brine mixed with flake ice, followed by those in liquid ice at 1.5 °C and ‐1.5 °C, respectively. Lowest counts were observed in shrimp stored in liquid ice at ‐1.5 °C where the lag phase of growth was apparently extended at the beginning of storage. Principal component analysis (PCA) showed a good correlation between quality indicators related to microbial growth, TVC, pH, TVB‐N, TMA, responses of an electronic nose and sensory evaluation.     

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。     

Mass spectrometry-based electric nose system for assessing rice quality during storage at different temperatures

A mass spectrometry-based electronic nose (MS e-nose) was used to measure changes in rice quality during storage at different storage conditions. Rice was stored for 4 months at four different temperatures (0 °C, 20 °C, 30 °C, and 40 °C) and tested for fat acidity, sensory characteristics, and flavor pattern analysis using the MS e-nose. When the rice was stored for long durations at higher temperatures, fat acidity increased and sensory quality was low. Flavor volatile profiles of the rice determined by MS e-nose revealed a tendency for the results to separate into three groups (months 1 + 2, 3, and 4). Volatile profile changes in rice during storage depended on the storage time, regardless of storage temperature. It is likely that the fat acidity and sensory evaluation results, which were related, could be distinguished by their volatile-producing metabolic activities. Accordingly, MS e-nose system was successfully used to screen and qualitatively evaluate stored rice.     

Storage studies on a sous vide spaghetti and meat sauce product

Shelf-life studies were done on a minimally processed sous vide spaghetti and meat sauce product subjected to a heat processing at 65°C and 75°C equivalent to a 5D and 13D reduction of Streptococcus faecium and subsequently stored at refrigeration (5°C) or under mild temperature abuse storage conditions (15°C). Products stored at 5°C had a shelf-life of ≥35 days irrespective of the processing treatment. However, for products stored at 15°C, packages were visibly swollen due to additional carbon dioxide production after 14 to 21 days, depending on the severity of the heat processing treatment, and the product had a distinct fruity odor when opened. Initial spoilage micro-organisms consisted predominantly of Bacillus species. However, after 7-12 days at 15°C, the spoilage pattern changed, with lactic acid bacteria accounting for almost all of the spoilage micro-organisms. As lactic acid bacteria increased in numbers, there was a concomitant increase in carbon dioxide and lactic acid production and a drop in pH of the product. This study has shown that physical, chemical and microbiological changes can be useful indicators to demonstrate temperature abuse of a minimally processed pasta product.     

Changes in some quality factors of frozen ginger as affected by the freezing storage conditions

The effects of types of ginger root, the freezing storage temperature and time on quality factors associated with color, off‐odor and acceptability of frozen ginger were evaluated to establish the freezing storage conditions of ginger roots. Whole and ground ginger was packed in Nylon/polyethylene (PE) bags and stored at ?5, ?20 and ?40 °C. The quality of the ginger was determined at the following times and storage temperatures: the ginger stored at ?5 °C, ?20 °C, and ?40 °C was sampled at 30‐day intervals for 4 months, at 90‐day intervals for 12 months, and at 120‐day intervals for 16 months, respectively. The content of free sugars, free amino acids (FAAs), unsaturated fatty acids (FUFAs) and volatile compounds noticeably decreased during the storage period, while the total color difference (ΔE) increased, and the temperature effect was significant. The changes in these compounds were generally less in the whole ginger samples. The overall preference of ginger roots stored at ?5, ?20 and ?40 °C was significantly different after 2–3, 9 and 16 months of storage, respectively. The increase of ΔE with decreases of free sugars, FAAs and sensory color indicated the discoloration of frozen ginger was due to the browning reaction. The sensory off‐odor scores were closely associated with the decrease of FUFAs, suggesting that the oxidation of FUFAs caused the development of off‐odor in the frozen ginger. Multiple regression analysis between the overall preference scores and other determined quality factors indicated that FAAs, FUFAs and volatile compounds significantly affected the overall preference scores of ground ginger samples stored at ?5 °C or ?20 °C. The sensory off‐odor and overall preference scores showed that whole ginger could be stored for 2 or 9 months at ?5 or ?20 °C, respectively, maintaining a good overall quality. Copyright © 2006 Society of Chemical Industry     

Evaluation of Shelf Life of Superchilled Cod (Gadus morhua) Fillets and the Influence of Temperature Fluctuations During Storage on Microbial and Chemical Quality Indicators

Quality changes of aerobically packed cod fillets stored under superchilling and abusive temperature conditions were characterized by the growth of specific spoilage organisms (SSO) and the production of microbial metabolites measured by an electronic nose along with traditional sensory and chemical analysis (total volatile basic nitrogen [TVB‐N], pH). A new process based on quick contact freezing and cold air blasting was used to achieve superchilling of fillets before chilled (0.5 °C) or superchilled (‐1.5 °C) storage. Photobacterium phosphoreum dominated under temperature abusive conditions coinciding with high levels of TVB‐N and increased electronic nose responses indicating increased levels of alcohols and aldehydes at sensory rejection. Dominating growth of Pseudomonas spp. in 1 batch was associated with the origin, the catching method, and the cooling conditions during processing. The superchilling process followed by superchilled storage (‐1.5 °C) extended the sensory shelf life of the fillets for at least 3 d compared with traditional process, resulting in a total shelf life of 15 d. High content of TVB‐N was observed in superchilled fillets at sensory rejection. P. phosphoreum counts were lower under superchilling conditions (6.0 to 6.8 log colony‐forming units [CFU]/g), compared with the traditionally processed chilled fillets (7.2 log CFU/g). However, H₂S‐producing bacteria appeared to grow steadily under superchilling conditions reaching counts as high as 7.6 log CFU/g at sensory rejection.     

基于电子鼻技术对冷藏后南果梨货架期间气味的变化分析

为研究南果梨冷藏后在货架期间气味的变化,采用电子鼻技术检测直接冷藏和经1-甲基环丙烯(1-MCP)处理后冷藏的南果梨在常温(20℃)货架期间挥发性物质的变化,分析直接冷藏和1-MCP处理再冷藏的南果梨挥发性物质的变化规律,并探讨电子鼻应用于检测南果梨挥发性物质的可能性。采用主成分分析法(PCA)、传感器贡献率分析(LA)、线性判别式分析法(LDA)进行分析,并建立特征雷达图。结果表明：电子鼻对南果梨的挥发性物质比较灵敏,可以利用电子鼻无损检测南果梨的挥发性物质的变化;经1-MCP处理的南果梨果实冷藏后在常温货架期间可以与未经处理的果实同样释放出南果梨特有的挥发性物质,但挥发性物质构成的变化速率有所减缓。     

高压静电场协同低温保鲜对莴笋贮藏品质影响及新鲜度的电子鼻无损检测研究

目的 研究高压静电场(high-voltage electrostatic field, HVEF)协同低温保鲜对莴笋贮藏品质的影响以及电子鼻对莴笋新鲜度的无损检测。方法 本研究以新鲜莴笋茎为研究对象,4℃协同HVEF冷藏保鲜为实验组,4℃常规冷藏保鲜为对照组,测定其贮藏期间感官评分、呼吸速率、硬度、失重率、色差、叶绿素含量和磁共振成像(magneticresonanceimaging,MRI),同时利用电子鼻结合主成分分析(principalcomponent analysis,PCA)和线性判别分析(lineardiscriminantanalysis,LDA)研究贮藏过程中不同新鲜度莴笋的挥发性气味变化。结果 HVEF组莴笋贮藏期可达35d。贮藏期间莴笋呼吸速率得到抑制,硬度、色泽、叶绿素、水分等品质得到较好的保持, PCA和LDA对不同新鲜度莴笋均有良好的区分效果。结论 HVEF协同低温保鲜能够减缓莴笋品质劣化,延长贮藏期;电子鼻结合PCA和LDA可对不同新鲜度莴笋进行区分,对莴笋贮藏过程中的无损检测具有重要意义。     

不同贮藏期冷却滩羊肉煮制后挥发性气味物质的变化

为研究不同贮藏期冷却滩羊肉煮制后挥发性气味物质的变化,采用固相微萃取-气相色谱-质谱结合电子鼻技术对0～4℃不同贮藏期(0、2、4、6、8、10 d)冷却滩羊肉煮制后产生的挥发性气味物质进行测定,并从宏观角度对挥发性气味物质的气味强度进行分析.最终共检测到38种挥发性气味物质,包括醛类19种、醇类11种、酮类4种、酸类...     

不同高温烹饪方式加工过程中滩羊肉风味化合物的差异比较

探讨滩羊肉高温烹饪（炒制、煎制、炸制）加工过程中挥发性风味化合物形成、变化及差异。在整体气味感知上,利用电子鼻可以区分生肉与炒制、煎制、炸制样品之间的不同气味。采用顶空固相微萃取-气相色谱-质谱（gas chromatography-mass spectrometry,GC-MS）对挥发性化合物进行定性分析,通过偏最小二乘判别分析（partial least squares-discrimination analysis,PLS-DA）法,辨别3?种加工方式不同加工阶段可挥发性成分组成。结果表明：在整体气味感知上,采用电子鼻可以区分3?种加工方式各个加工阶段,在炒制煸炒脂肪出油阶段、煎制1?min阶段、炸制3?min阶段响应值最强。GC-MS鉴定滩羊高温烹饪肉制品挥发性化合物273?种,其中炒制174?种,炸制158?种,煎制134?种。煎制、炸制前期就产生了大量的挥发性风味物质,而炒制是在加工后期才产生大量的挥发性风味物质。PLS-DA评分散点图将原料肉、3?种加工方式的滩羊肉制品挥发性化合物区分开,且有各自清晰的气味特征。醛类是3?种滩羊肉制品主要的挥发性化合物,己醛的浓度含量最高。炒制煸炒脂肪出油阶段增加了滩羊肉的可挥发性风味化合物种类及相对含量,对风味的整体贡献最高,尤其是酸类、酯类、杂环类化合物的贡献。     

Optimization of a HS-SPME-GC-MS Procedure for Beer Volatile Profiling Using Response Surface Methodology: Application to Follow Aroma Stability of Beers Under Different Storage Conditions

The optimization of the main experimental variables, such as extraction temperature, volume of sample and the extraction time of an HS-SPME/GC-MS procedure, for profiling beer volatile analysis was evaluated using response surface methodology. A central composite circumscribed design was employed to study the effect of the experimental variables on the extraction of 28 representative volatile compounds of beer flavour profile. The parameters of the models were estimated by multiple linear regressions. The strongest influence in the volatile extraction yield was the volume of the sample (V) and the extraction temperature (T), with a positive and a negative effect, respectively. The performance characteristics of the optimised method were also determined, showing adequate linear ranges, repeatability, detection and quantification limits. The optimised methodology was applied to the same beer sample stored during 5?months at three different temperature conditions (4, 20 and 40?°C). Sampling was performed monthly, and the results showed that the concentration of most volatile compounds decreased during beer storage, although the rate of decrease was clearly higher at room temperature (20?°C) compared with refrigeration conditions (4?°C). Accelerated ageing conditions (40?°C) showed the most different volatile profile. Sensory analysis also revealed large differences in the overall quality of the samples, showing that even at room temperature the aroma profile of beer is greatly modified during its shelf life.