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1.
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2.
Mozzarella cheese obtained from buffalo (Bubalus bubalis) milk is a typical Italian product certificated by means of the European Protected Designation of Origin (PDO). Mozzarella cheese can also be obtained from bovine milk or bovine/buffalo milk mixtures, but in this case, it cannot be sold as PDO product, and its label must report the actual ingredients. However, bovine milk in PDO products was frequently detected in the past, suggesting fraudulent addition or accidental contamination. Several methods based on end-point polymerase chain reaction (PCR) have been profitably applied in a large number of tests to detect the presence of undeclared ingredients, also in dairy products. In the present study we report a real-time PCR method able to quantify bovine milk addition to pure buffalo cheese products. We validated a normalized procedure based on two targets: bovine mitochondrial cytochrome b (cyt b) to detect and quantify the bovine DNA and nuclear growth hormone (GH) gene used as a universal reference marker. With the use of this real-time PCR assay, 64 commercial mozzarella di bufala cheese samples purchased at local supermarkets, dairy shops, or directly from cheese manufacturers were analyzed. The results obtained demonstrate that most of the commercial samples were contaminated with bovine milk. Therefore, this assay could be conveniently employed to carry out routine and accurate controls aimed not only to discourage any fraudulent behavior but also to reduce risks for consumer health.  相似文献   

3.
基于近红外光谱的脐橙产地溯源研究   总被引：2，自引：1，他引：1  
为研究近红外光谱分析技术鉴别脐橙产地的可行性,该文采用江西、重庆和湖南3个产地脐橙样品1140～1170nm波段的近红外光谱经一阶导数(9点平滑)预处理,分别建立了簇类独立软模式法脐橙产地鉴别模型。在5%显著水平下,模型对3个产地训练集样品的识别率均为100%,拒绝率分别为85.7%、83.3%、100%;对验证集样品的识别率均为100%,拒绝率分别为100%、89.5%、100%,表明簇类独立软模式法模型基本能够判别脐橙产地。将江西、重庆和湖南3个产地的脐橙样品分别赋值0、1、?1,在全波段范围内建立原始光谱脐橙产地的偏最小二乘判别模型,其预测值与真实值的决定系数为0.973,校正标准差为0.110,预测标准差为0.159,模型对训练集和验证集样品的识别率达到100%。因此,应用近红外光谱分析技术可准确、快速地追溯脐橙产地来源。  相似文献   

4.
Optimum conditions of solid phase microextraction (SPME) analysis of the headspace volatile compounds of Parmesan cheese in airtightly sealed 100-mL bottles were developed. The coefficient of variation of SPME analysis on the headspace volatile compounds of Parmesan cheese was 2%. The reproducibility of SPME was improved by a combination of sampling at -10 degrees C, controlling the sample temperature, and uniform magnetic stirring of samples during equilibrium and isolation steps. The sensitivity of SPME increased by 125% in total peak areas by a combination of 40 min of sonication and 25% (w/v) sodium phosphate solution, compared with that of samples containing deionized water only (P < 0.05). The addition of salt solution or sonication treatment in samples increased the headspace volatile compounds of cheese quantitatively without producing any new volatile compounds.  相似文献   

5.
Headspace solid-phase microextraction (HS-SPME) -gas chromatography using flame ionization detection and multivariate analysis were applied to the study of the specificity of protected designation of origin (PDO) virgin olive oils produced in a southern French region (Alpes-Maritimes) based on their volatile compounds. A total of 35 PDO olive oils from Nice, 6 commercial oils, and 12 other French PDO olive oils were analyzed. Recorded data were subjected to principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). The method developed here was able to perfectly distinguish different qualities of olive oils. Representative samples from each class obtained by chemometric treatment were analyzed by HS-SPME and GC-MS. PCA and SIMCA of chromatographic data were related to sensory analysis and led to a better understanding of the chemical features and observed sensory effects of olive oils.  相似文献   

6.
The content of benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon, was determined by HPLC-FL in "mozzarella di bufala campana" cheese, a stretched cooked cheese, either experimentally smoked according to traditional procedures, using straw, cardboard, and wood shavings or aromatized with smoke flavoring. The BaP residues, researched also in cheese samples sold at retail, were detected in the rind, in the core, and in the slice (outer and inner parts). In the cheeses experimentally smoked with straw and cardboard the BaP levels, ranging from 0.38 to 2.12 microg kg(-1) and from 0.46 to 2.40 microg kg(-1), respectively, were statistically higher than those of the cheeses smoked with wood shavings and aromatized with liquid smoke (from 0.19 to 0.80 microg kg(-1) and from 0.18 to 0.50 microg kg(-1), respectively). However the cheeses treated with liquid smoke flavor showed a BaP content exceeding the level allowed by the European Union. In the samples sold at retail, smoked with straw, values were lower than those obtained from samples smoked experimentally with the same combustible. This is probably due to different smoking technologies among the several provinces of the Protected Designation of Origin (PDO) area. PDO is a term used to characterize foodstuffs produced and prepared in a given geographical region by the means of a recognized process. A standardization of the traditional smoking procedures and an improvement of liquid smoke purification treatments are recommended for mozzarella cheese.  相似文献   

7.
Light-induced volatile compounds in goat cheese were studied by a combination of solid phase microextraction (SPME)-gas chromatography (GC)-mass spectrometry (MS), headspace oxygen depletion, and sensory evaluation. Samples stored under fluorescent light for 2 days at 30 degrees C had 90% more volatile compounds and 4 times more headspace oxygen depletion than samples stored in the dark at 30 degrees C. The volatiles 1-heptanol, heptanal, nonanal, and 2-decenal were formed and increased only in the light-stored samples, which may be formed from singlet oxygen oxidation of unsaturated fatty acids. Sensory evaluation showed that samples stored under light had significantly more off-flavor than samples stored in the dark at 30 degrees C (P < 0.05), and 1-heptanol, heptanal, nonanal, and 2-decenal increased the goat cheese off-flavor significantly (P < 0.05).  相似文献   

8.
Visible (vis) and near-infrared (NIR) spectroscopy combined with multivariate analysis was used to classify the geographical origin of commercial Tempranillo wines from Australia and Spain. Wines (n = 63) were scanned in the vis and NIR regions (400-2500 nm) in a monochromator instrument in transmission. Principal component analysis (PCA), discriminant partial least-squares discriminant analysis (PLS-DA) and linear discriminant analysis (LDA) based on PCA scores were used to classify Tempranillo wines according to their geographical origin. Full cross-validation (leave-one-out) was used as validation method when PCA and LDA classification models were developed. PLS-DA models correctly classified 100% and 84.7% of the Australian and Spanish Tempranillo wine samples, respectively. LDA calibration models correctly classified 72% of the Australian wines and 85% of the Spanish wines. These results demonstrate the potential use of vis and NIR spectroscopy, combined with chemometrics as a rapid method to classify Tempranillo wines accordingly to their geographical origin.  相似文献   

9.
An instrumental method for the evaluation of olive oil quality was developed. Twenty-one relevant aroma active compounds were quantified in 95 olive oil samples of different quality by headspace solid phase microextraction (HS-SPME) and dynamic headspace coupled to GC-MS. On the basis of these stable isotope dilution assay results, statistical evaluation by partial least-squares discriminant analysis (PLS-DA) was performed. Important variables were the odor activity values of ethyl isobutanoate, ethyl 2-methylbutanoate, 3-methylbutanol, butyric acid, E,E-2,4-decadienal, hexanoic acid, guaiacol, 2-phenylethanol, and the sum of the odor activity values of Z-3-hexenal, E-2-hexenal, Z-3-hexenyl acetate, and Z-3-hexenol. Classification performed with these variables predicted 88% of the olive oils' quality correctly. Additionally, the aroma compounds, which are characteristic for some off-flavors, were dissolved in refined plant oil. Sensory evaluation of these models demonstrated that the off-flavors rancid, fusty, and vinegary could be successfully simulated by a limited number of odorants.  相似文献   

10.
The characterization of amaranth seeds (Amaranthus spp.) was developed for Amaranthus hypochondriacus, Amaranthus cruentus, and Amaranthus dubius. The elemental concentrations were determined by inductively coupled plasma optic atomic spectroscopy. Pattern recognition methods were used for the characterization of seed samples: nonsupervised methods included principal components analysis and cluster analysis; supervised methods were linear discriminant analysis and partial least squares discriminant analysis (PLS-DA). Informed are the concentrations of the following elements: Ag, Al, Ba, Ca, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Mo, Na, Ni, P, S, Sr, V, Zn, and Zr. The lowest mineral content was found in A. hypochondriacus, and the highest one was found in A. dubius. For the classification, selected variables for all multivariate methods were Ba, Cr, Li, Mn, Ni, S, and Sr. Nonsupervised methods allowed us to distinguish between the three species of amaranth; however, PLS-DA supervised methods showed the best prediction ability.  相似文献   

11.
A headspace solid-phase microextraction (HS-SPME) and gas chromatography-selective ion monitoring/mass spectrometry (GC-SIM/MS) method was optimized for analysis of 22 volatile compounds in orujo spirit samples from the Geographic Denomination "Orujo de Galicia/Augardente de Galicia". HS-SPME experimental conditions, such as fiber coating, extraction temperature, extraction and pre-equilibrium time, sample volume, and the presence of salt, were studied to improve the extraction process. The best results were obtained using a 65 microm Carbowax-divinylbenzene fiber during a headspace extraction at 40 degrees C with constant magnetic stirring for 15 min and after a 5 min period of pre-equilibrium time. The sample volume was 6 mL of orujo containing 25% of NaCl, placed in 12 mL glass vials equipped with a screw cap and PTFE/silicone septum. Desorption was performed directly in the gas chromatograph injector port for 5 min at 250 degrees C using the splitless mode. The proposed method is sensible (with detection limits between 0.0045 and 0.2399 mg/L), precise (with coefficients of variation in the range 0.99-8.18%), and linear over more than 1 order of magnitude. The developed method presented recoveries comprised between 76.0 and 112.4%. The applicability of the new method was demonstrated by determining the considered 22 volatile compounds in nine orujo commercial samples with quality and origin brands.  相似文献   

12.
The influences of fluorescent light exposure and packaging atmosphere on the headspace volatiles and color of Cheddar cheese shreds were evaluated using gas chromatography-mass spectrometry and spectrocolorimetry, respectively. Cheddar cheeses were packaged under atmospheres of 100% carbon dioxide or 100% nitrogen and stored at 4 degrees C under fluorescent light for 6 weeks. Cheeses stored under carbon dioxide contained higher concentrations of aldehydes and fatty acids and lower concentrations of alcohols and esters than cheeses stored under nitrogen. Carbon dioxide atmospheres potentiated light-induced oxidation in shredded Cheddar cheeses, as evidenced by aldehyde and fatty acid headspace volatiles measured following storage. Color bleaching occurred only in cheeses packaged under carbon dioxide and exposed to light. The shift in color is proposed to be due to an interaction between carbon dioxide and high-intensity light, leading to the oxidation of the pigment molecule, bixin. The results have significant implications for procedures used to handle and store pigmented cheeses to ensure desirable flavor and consumer acceptability.  相似文献   

13.
Gas chromatography-olfactometry (GC-O) and proton transfer reaction-mass spectrometry (PTR-MS) techniques were used to deduce the profile of odor-active and volatile compounds of three grana cheeses: Grana Padano (GP), Parmigiano Reggiano (PR), and Grana Trentino (GT). Samples for GC-O analysis were prepared by dynamic headspace extraction, while a direct analysis of the headspace formed over cheese was performed by PTR-MS. The major contributors to the odor profile were ethyl butanoate, 2-heptanone, and ethyl hexanoate, with fruity notes. A high concentration of mass 45, tentatively identified as acetaldehyde, was found by PTR-MS analysis. Low odor threshold compounds, e.g., methional and 1-octen-3-one, which contributed to the odor profile but were not detected by FID, were detected by PTR-MS. Principal component analysis on both GC-O and PTR-MS data separated the three cheese samples well and showed specific compounds related to each sample.  相似文献   

14.
利用近红外高光谱图像技术快速鉴别西瓜种子品种   总被引：12，自引：8，他引：4  
为了研究采用近红外高光谱图像技术对西瓜种子品种快速无损鉴别的可行性,该文采用近红外高光谱图像技术,通过提取西瓜种子的光谱反射率,结合Savitzky-Golay (SG)平滑算法,经验模态分解算法（empirical mode decomposition,EMD）和小波分析（wavelet transform,WT）对提取出的光谱数据进行去除噪声处理,采用连续投影算法（successive projections algorithm,SPA）和遗传-偏最小二乘法（genetic algorithm-partial least squares, GA-PLS）进行特征波长选择。基于全波段光谱建立了偏最小二乘判别分析（partial least squares-discriminant analysis,PLS-DA）,基于特征波长建立了反向传播神经网络（back-propagation neural network,BP NN)判别模型和极限学习机（extreme learning machine,ELM）判别模型。试验结果表明,基于特征波长的BPNN模型和ELM模型的结果优于基于全部波长的PLS-DA模型,基于SG预处理光谱提取的特征波长建立的ELM模型取得最优的判别效果,建模集和预测集的判别正确率均为100%。结果表明应用近红外高光谱成像技术对西瓜种子品种鉴别是可行的,为西瓜种子的品种快速鉴别提供了一种新方法。  相似文献   

15.
In the present work, a rapid and simple NMR method to discriminate Asiago d'Allevo cheese samples from different production chains is described. A fast and reproducible extraction of the organic fraction was employed. By applying chemometric analysis to NMR data, it is possible to differentiate PDO Asiago cheese produced in alpine farms from that produced in lowland and mountain industrialized factories. PCA of both (1)H and (13)C NMR spectra showed a good separation of alpine farm products from the other ones, whereas the lowland and mountain industrialized cheeses are undistinguishable. The samples were differentiated on the basis of a higher content of unsaturated fatty acids, principally oleic, linoleic, linolenic, and conjugated linoleic acids for the alpine farm cheeses and a higher content of saturated fatty acids for the industrialized products. Conjugated linoleic acid and 1-pentene are also discriminating components.  相似文献   

16.
Production of volatile compounds by seven Pseudomonas strains belonging to six different species, Ps. brenneri, Ps. graminis, Ps. libanensis, Ps. lundensis, Ps. putida, and Ps. rhodesiae, was investigated, with the aim of elucidating their possible contribution to the volatile profile of cheese. Laboratory-scale cheeses were made from pasteurized milk of low bacterial counts separately inoculated with approximately 10(5) colony-forming units/mL of each Pseudomonas strain and ripened for 12 days at 10 degrees C. A total of 122 volatile compounds were identified in cheeses by GC-MS of the dynamic headspace. The abundance of 62 compounds, belonging to eight chemical groups (aldehydes, ketones, acids, esters, alcohols, hydrocarbons, benzene compounds, and sulfur compounds) increased during ripening for at least one of the strains. Most groups of volatile compounds were more abundant in the outer part of cheeses than in the inner part, in agreement with the aerobic metabolism of the genus Pseudomonas and coinciding with the higher counts in the outer part. Production of volatile compounds in cheese by Pseudomonas was shown to be species-dependent.  相似文献   

17.
Clementine is a citrus fruit that has found a peculiar habitat in specific areas of Calabria, a region located in southern Italy. Due to its peculiar characteristics it was recently awarded with protected geographical indications (PGI) from the European Union. In this work, stepwise linear discriminant analysis (S-LDA), soft independent modeling of class analogy (SIMCA), and partial least-squares discriminant analysis (PLS-DA) were used to build chemometric models able to protect PGI Clementine from others of different origin. Accordingly, the concentration of 24-26 elements was determined in peel and juice samples, respectively, obtained from Calabrian PGI clementine and from fruits cultivated in Algeria, Tunisia, and Spain. A cross-validation procedure has shown very satisfactory values of prediction ability for both S-LDA (96.6% for juice samples and 100% for peel samples) and SIMCA (100% for both peel and juice samples). PLS-DA models also yielded satisfactory results.  相似文献   

18.
This work focused on developing a method to determine the volatile compounds that contribute to individual masses observed by PTR-MS in the headspace of a food product (e.g., cheese crackers). The process of interfacing a PTR-MS with a GC-MS (electron impact) through an existing sniffing port is outlined, and the problems faced in doing so are discussed. For the interface developed, linearity for both detectors working online for a wide range of concentrations of a selected compound (hexanal) was good (R(2) = 0.88). There was also a good correlation between the responses for both instruments (confidence interval for the slope between 0.56 and 1.18) over a range in concentrations despite the different ionization processes taking place. The application of our system (PTR-MS/GC-MS interface) to a real food system (cheese crackers) in which volatiles were isolated via purge and trap allowed the assignments of most of the PTR-MS masses to major volatile compounds in the samples. However, in this interface it is important to consider some limitations related to GC resolution, compound identification by EI-MS, PTR-MS sensitivity (and overloading), PTR-MS inlet requirements (ca. 20 mL/min), ion chemistry in the PTR-MS, and potentially changing sample composition over time, altering the contribution of a given compound to a specific ion. These issues are discussed.  相似文献   

19.
Aroma compounds of 48 Sherry brandies have been identified and quantified by the stir bar sorptive extraction method coupled to gas chromatography-mass spectrometry (SBSE-GC/MS). Analysis of variance and multivariate analysis techniques have been used to classify these brandy samples according to the commercial category (Solera brandy, Solera Reserva brandy, and Solera Gran Reserva brandy). From an univariate point of view (analysis of variance), several of the volatile compounds considered showed significant differences. Principal component analysis, using the global data matrix, showed that only the Solera brandy samples, with the shortest aging in wood, were well-differentiated from the others. Partial least-squares discriminant analysis (PLS-DA) results provided evidence of the ability of the content of volatile compounds to discriminate among the different commercial categories. Linear discriminate analysis allowed for a 93% differentiation according to the commercial category and, thus, the length of its aging process in wood. The results obtained show that it would be possible to ensure the commercial category of a Sherry brandy using its content of volatile compounds.  相似文献   

20.
Fifty volatile compounds of surface smear-ripened cheese were detected and identified using headspace solid-phase microextraction (HS-SPME) and vacuum distillation coupled to gas chromatography-mass spectrometry. Changes in the headspace of aroma compounds were monitored over the whole packaging period (47 days) using the HS-SPME method. Initially, the concentration of methanethiol increased before reaching a plateau. This evolution could be linked to the growth of Brevibacterium linens. During the shelf life of cheese, levels of acetic acid and 3-methylbutanoic acid remained constant, whereas butane-2,3-dione, 3-hydroxybutan-2-one, and hydroxypropan-2-one levels gradually declined and acetone and 3-methylbutanol levels dropped sharply to a plateau. Changes in odor could be related to changes of the rind, which behaved as a barrier, strongly influencing the distribution of volatile compounds in the headspace. Using a gas chromatography-olfactometry technique without separation, it was shown that the SPME extract was representative of the cheese odor.  相似文献   

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