Synchronous front-face fluorescence spectroscopy as a promising tool for the rapid determination of spoilage bacteria on chicken breast fillet

In this work the potential of synchronous front-face fluorescence spectroscopy along chemometric methods was investigated for the determination of microbial load on chicken breast fillets stored aerobically at 5 °C during 0, 1, 2, 3, 5 and 8 days, and 15 °C for 0, 0.5, 1, 2, 3 and 5 days. Total viable count (TVC), Pseudomonas, Enterobacteriaceae and Brochothrix thermosphacta were determined on chicken breast fillets at each step of the 2 kinetics using culture dependent methods. Initial TVC was 3.4 log cfu/cm² and TVC reached 8.4 log cfu/cm² and 8.3 log cfu/cm² following 8 days at 5 °C and 2 days at 15 °C, respectively. In parallel, synchronous fluorescence spectra were recorded in an excitation wavelength range of 250-500 nm using offsets of 20, 40, 60,…, 180 nm between excitation and emission monochromators. PARAFAC (parallel factor) analysis allowed to capture the changes occurring in the synchronous fluorescence spectral data. The best PARAFAC models showed 3 and 2 components for kinetics recorded at 5 and 15 °C, respectively. PLSDA (partial least square discriminant analysis) was carried out to test the reallocation of the spectra of the individual samples within the six groups corresponding to the six investigated storage times and the results showed that 100% of good classifications were obtained using 4 PLS factors. Finally, N-PLS regression was used to predict the microbial counts for TVC, Pseudomonas, Enterobacteriaceae and B. thermosphacta from the spectral data. Good average recoveries of 100 to 102%, excellent correlations (R² = 0.99) and very small root mean squares errors (between 0.1 and 0.2 log cfu/cm²) of prediction were obtained from the spectral data sets recorded on samples stored at 5 °C and 15 °C for TVC, Pseudomonas, Enterobacteriaceae and B. thermosphacta.     

Analysis of visible reflectance spectra of stored, cooked and diseased chicken meats

Visible spectra of cold stored, cooked, and diseased chicken meats were collected. Changes in ratios of R₁=A_{485 nm}/A_{560 nm} and R₂=A_{635 nm}/A_{560 nm,} which are related to absorbances of the bands at 485 (metmyoglobin), 560 (oxymyoglobin), and 635 nm (sulfmyoglobin), were observed to be useful for studying the variation of meat color under the conditions of cold storage and cooking process. Such a strategy was also applied to classify fresh-raw wholesome and unwholesome meats into respective classes, and the result was compared with that produced from a chemometric model. The strategy might be used as a simple methodology for monitoring the color variation of meats where the development of the chemometric model is either impractical or not desirable.     

Evidence for a role of biosurfactants produced by Pseudomonas fluorescens in the spoilage of fresh aerobically stored chicken meat

Fresh chicken meat is a fat-rich environment and we therefore hypothesised that production of biosurfactants to increase bioavailability of fats may represent one way in which spoilage bacteria might enhance the availability of nutrients. Numbers of Pseudomonas were determined on a total of 20 fresh and 20 spoiled chicken thighs with skin. A total of 400 randomly isolated Pseudomonas colonies from fresh (200) and spoiled (200) chicken were screened for the presence of biosurfactant production. Biosurfactant producing strains represented 5% and 72% of the Pseudomonas spp. isolates from fresh (mean count 2.3 log₁₀ cfu g⁻¹) and spoiled (mean count 7.4 log₁₀ cfu g⁻¹) chicken skin, respectively. Partially-purified biosurfactants derived from a subgroup of four Pseudomonasfluorescens strains obtained through the screening process were subsequently used to investigate the role that the addition of these compounds plays in the spoilage of aerobically stored chicken. Emulsification potential of the four selected biosurfactants was measured against a range of hydrocarbons and oils. All four biosurfactants displayed a greater ability to emulsify rendered chicken fat than hydrocarbons (paraffin liquid, toluene and hexane) and oils (canola, olive, sunflower and vegetable). Storage trials (4 °C) of chicken meat treated with the four selected biosurfactants revealed a significantly greater (P < 0.05) total aerobic count in biosurfactant treated samples, as compared to untreated samples on each day (0, 1, 2, 3) of storage. For biosurfactant treated samples the greatest increase in total aerobic count (1.3-1.7 log₁₀ cfu g⁻¹) occurred following one day of incubation. These results indicate that biosurfactants produced by Pseudomonas spp. may play an important role in the spoilage of aerobically stored chicken meat by making nutrients more freely available and providing strains producing them with a competitive advantage.     

At-line prediction of fatty acid profile in chicken breast using near infrared reflectance spectroscopy

Near infrared reflectance (NIR) spectroscopy was evaluated as at-line technique to predict FA profile of chicken breast directly at the slaughterhouse. Intact breasts of 214 chickens were scanned by applying a fiber optic probe to the Pectoralis superficialis muscle. Meat samples were analyzed by gas chromatography as the reference method for the determination of FA composition. Calibration equations were developed considering NIR wavelengths between 1100 and 1830 nm, and modified partial least square (MPLS) was chosen as the chemometrics method to perform the calibrations. Different mathematical pre-treatments were tested and the best calibration equation for each FA was retained. Near infrared reflectance spectroscopy did not result in satisfactory predictions of FA. The best predictions were observed for oleic acid (C18:1n-9), monounsaturated FA (MUFA), and polyunsaturated FA (PUFA), and for a few minor FA. Results suggest that for chicken breast muscle, a lean meat, it was not possible to predict FA using NIR spectroscopy as an at-line technique in the abattoir.     

Contribution of Fourier transform infrared (FTIR) spectroscopy data on the quantitative determination of minced pork meat spoilage

The aim of this work was to investigate the feasibility of Fourier transform infrared (FTIR) spectroscopy to quantify biochemical changes occurring in fresh minced pork meat in the attempt to monitor spoilage. For this reason, partial least squares (PLS) models were constructed to correlate spectral data from FTIR with minced pork meat spoilage during aerobic storage of meat samples at different storage temperatures (0, 5, 10, and 15 °C). Spectral data were collected from the surface of meat samples in parallel with microbiological analysis to enumerate the population of total viable counts, Pseudomonas spp., Brochothrix thermosphacta, lactic acid bacteria and Enterobacteriaceae. Qualitative interpretation of spectral data was based on sensory evaluation, using a three point hedonic scale, discriminating meat samples in three quality classes, namely fresh, semi-fresh and spoiled. The purpose of the developed models was to classify minced pork samples in the respective quality class, and also to correlate the population dynamics of the microbial association with FTIR spectra. The obtained results demonstrated good performance in classifying meat samples in one of the three pre-defined sensory classes. The overall correct classification rate for the three sensory classes was 94.0% and 88.1% during model calibration and validation, respectively. Furthermore, PLS regression models were also employed to provide quantitative estimations of microbial counts during meat storage. The performance was based on graphical plots and statistical indices (bias factor, accuracy factor, standard error of calibration, standard error of prediction, and correlation coefficient). The values of the bias factor were close to unity for all microbial groups indicating no systematic bias of the models. Moreover, the calculated values of the accuracy factor showed that the average deviation between predictions and observations was 7.5% and 7.9% for total viable counts and Pseudomonas spp. and 10.7% and 11.3% for lactic acid bacteria and B. thermosphacta. Finally, correlations above 0.80 between observed and estimated counts were observed for both training and test data sets.     

Rapid monitoring of the spoilage of minced beef stored under conventionally and active packaging conditions using Fourier transform infrared spectroscopy in tandem with chemometrics

Fourier transform infrared (FTIR) spectroscopy was exploited to measure biochemical changes within fresh minced beef in an attempt to rapidly monitor beef spoilage. Minced beef packaged either aerobically, under modified atmosphere and using an active packaging were held from freshness to spoilage at 0, 5, 10, and 15 °C. Frequent FTIR measurements were collected directly from the sample surface using attenuated total reflectance, in parallel the total viable counts of bacteria, the sensory quality and the pH were also determined.     

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.     

鸡腿肌冻干粉蛋氨酸近红外光谱定量预测模型的建立与优化

本文从光谱预处理方法、建模特征光谱筛选、异常样本剔除、建模样本选择四个方面建立和优化鸡腿肌冻干粉蛋氨酸近红外定量预测模型,旨在进一步提高模型的预测精度和模型稳健性。以263个鸡腿肌冻干粉NIRS和蛋氨酸含量为研究对象,分别使用7种不同光谱预处理方法、4种特征光谱筛选方法、2种MCCV异常样本剔除方法,SPXY和常规选择2种建模样本选择方法,应用偏最二小乘法(PLS)、内部交互验证和外部验证建立和优化腿肌冻干粉蛋氨酸近红外定量预测模型。结果表明：在本研究中,最优鸡腿肌冻干粉蛋氨酸NIRS定量预测模型为在1000-2502nm谱段,使用原始光谱,在SNV+gapsegment(1#,15,7)光谱的基础上使用MCCV方法删除54个样本后,采用SPXY方法选取156个校正样本,39个外部验证样本所建模型,其为0.93、SE_CV为0.0609、为0.83、RPD_P为2.42。研究表明,模型预测值与化学检测值有很高的相关度,对腿肌冻干粉蛋氨酸NIRS模型预测精度和稳健性影响最大因素是异常样本剔除方法和建模样本选取方法。     

基于傅里叶变换红外光谱法的红花药材质量分析

目的 建立傅里叶变换红外光谱法分析评价红花药材质量的分析方法。方法 采用傅立叶变换红外光谱法(Fourier transform infrared spectrometry, FTIR)对采集自新疆不同产地的20批红花药材进行测量, 建立指纹图谱; 运用聚类分析与主成分分析等统计学及化学模式识别技术, 对不同来源的红花药材进行红外光谱数据比较分析。结果 筛选出12个波数段, 形成了红花药材FTIR红外光谱指纹图谱共有模式; 精密度、稳定性和重复性实验结果表明, 共有峰波数的相对标准偏差(relative standard deviation, RSD)分别为0.00%~0.1%、0.00%~4.56%、0.32%~7.5%, 符合指纹图谱的要求; 20批样品相似度均大于95%, 大致可以分为3大类, 区域间差异较为明显。结论 本研究建立的方法简单、易行、快速, 不污染、样品耗量低, 为不同来源红花药材的鉴定、内在质量评价与质量控制提供了依据、奠定了基础。     

Application of Fourier transform infrared spectroscopy to legume seed flour analysis

The secondary structure of legume (Phaseolus vulgaris L. and Lens culinaris L.) proteins was investigated by studying the amide I infrared absorption band in whole seed flours, before and after dry heating and autoclaving thermal treatments. The analysis procedure, set up on 7S and different model proteins, shows that the content of β-sheet structures in lentil is higher than in common bean (47% vs. 32%). The dry heating does not appreciably affect secondary structures in lentil, while it causes a reduction of β-sheets (to 13%), an increase of aggregates, and the appearance of random coil structures in common bean. The autoclaving treatment produces high amounts of aggregates in both legumes. However, in lentil, random coil structures are lower than in common bean and some β-sheet structures are still detectable. These results indicate that multimeric heat-induced complexes of legume proteins have a high stability because of the high content in β-sheet structures, in particular in lentil, which may adversely affect protein utilization.     

Combined effect of oregano essential oil and modified atmosphere packaging on shelf-life extension of fresh chicken breast meat, stored at 4 degrees C

The combined effect of oregano essential oil (0.1% and 1% w/w) and modified atmosphere packaging (MAP) (30% CO2/70% N2 and 70% CO2/30% N2) on shelf-life extension of fresh chicken meat stored at 4 degrees C was investigated. The parameters that were monitored were: microbiological (TVC, Pseudomonas spp., lactic acid bacteria (LAB), yeasts, Brochothrix thermosphacta and Enterobacteriaceae), physico-chemical (pH, TBA, color) and sensory (odor and taste) attributes. Microbial populations were reduced by 1-5 log cfu/g for a given sampling day, with the more pronounced effect being achieved by the combination of MAP and oregano essential oil. TBA values for all treatments remained lower than 1 mg malondialdehyde (MDA) kg(-1) throughout the 25-day storage period. pH values varied between 6.4 (day 0) and 5.9 (day 25). The values of the color parameters L*, a* and b* were not considerably affected by oregano oil or by MAP. Finally, sensory analysis showed that oregano oil at a concentration of 1% imparted a very strong taste to the product for which reason these lots of samples were not scored. On the basis of sensory evaluation a shelf-life extension of breast chicken meat by ca. 3-4 days for samples containing 0.1% oregano oil, 2-3 days for samples under MAP and 5-6 days for samples under MAP containing 0.1% of oregano oil was attained. Thus oregano oil and MAP exhibited an additive preservation effect.     

The use of visible and near infrared reflectance spectroscopy to predict beef M. longissimus thoracis et lumborum quality attributes

Visible and near infrared reflectance spectroscopy was used to predict pH at 24 h (pH24) post-mortem, sarcomere length (SL), cooking loss (CL), Warner–Bratzler Shear Force (WBSF) and colour parameters (L^∗, a^∗, b^∗) in beef cattle samples. Samples from M. longissimus thoracis et lumborum from 30 bulls were aged at 4 °C for 1, 3, 7 and 14 days and analysed for pH, SL, CL, WBSF and colour. NIRS calibrations for pH24, luminosity at 0 (L^∗t0) and 60 min (L^∗t60) showed good predictability (R² = 0.97, 0.85 and 0.82; SECV = 0.10, 1.16, 1.36, respectively), whereas those related to the rest of the parameters were poorer.     

Effect of ripening with Penicillium roqueforti on texture,microstructure, water distribution and volatiles of chicken breast meat

In this study, the influence of ripening with Penicillium roqueforti on texture, microstructure, protein structure, water mobility and volatile flavour compounds of chicken breast meat was investigated. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) images showed that the granule formed and chicken myofibril fractured after ripening. Reduction in α-helix and increases in β-sheet structure content accompanied by decrease in hardness and springiness and increase in gumminess were found in ripened chicken breast meat. Low field nuclear magnetic resonance (LF-NMR) revealed that increasing intra-myofibrillar water and decreasing extra-myofibrillar water resulted in the higher water-holding capacity after ripening with P. roqueforti. In addition, chicken breast meat ripened with P. roqueforti contained more volatile flavour compounds, in particular aldehydes.     

Effect of rosemary on lipid oxidation in pressure-processed,minced chicken breast during refrigerated storage and subsequent heat treatment

The protective effect of rosemary (Rosmarinus officinalis L.) against lipid oxidation and tocopherol degradation in minced, pressure-processed chicken breast with 0.5% salt added was investigated during chill storage for 9 days and/or subsequent heat treatment by measurement of head-space hexanal and pentanal together with thiobarbituric acid reactive substances (TBARS) and α- and γ-tocopherol. High-pressure processing at 600 MPa for 10 min led to a significant increase in secondary lipid oxidation products in minced chicken breast without rosemary, when compared to chicken breast with rosemary added. During subsequent chill storage, the level of secondary lipid oxidation products decreased slightly. For samples heated after pressure treatment and chill storage to mimic cooking, levels of secondary lipid oxidation products were higher than for the uncooked samples and rosemary was very efficient in preventing the oxidative process also during cooking, while the length of the chill storage period prior to cooking had little effect. Higher levels of α- and γ-tocopherol were found in all samples with rosemary compared to samples without rosemary, indicating that rosemary also protects tocopherols against degradation in pressurized chicken breast during chill storage and/or subsequent heat treatment.     

Classification of Pecorino cheeses produced in Italy according to their ripening time and manufacturing technique using Fourier transform infrared spectroscopy

Fourier-transform infrared spectroscopy, followed by linear discriminant analysis of the spectral data, was used to classify Italian Pecorino cheeses according to their ripening time and manufacturing technique. The Fourier transform infrared spectra of the cheeses were divided into 18 regions and the normalized absorbance peak areas within these regions were used as predictors. Linear discriminant analysis models were constructed to classify Pecorino cheeses according to different ripening stages (hard and semi-hard) or according to their manufacturing technique (fossa and nonfossa cheeses). An excellent resolution was achieved according to both ripening time and manufacturing technique. Also, a final linear discriminant analysis model considering the 3 categories (hard nonfossa, hard fossa, and semi-hard nonfossa) was constructed. A good resolution among the 3 categories was obtained.     

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...