Brazil is one of the most important countries as a producer and exporter of cattle and poultry. I... more Brazil is one of the most important countries as a producer and exporter of cattle and poultry. In 2009 cattle accounted for 30% of the export market and 41.4% for poultry meat. The Brazilian National Residues and Contaminants Control Plan (PNCRC) follows the guidelines set by the Codex Alimentarius Commission and checks compliance maximum residue limits (MRLs) to ensure the quality of these commodities. Kidney samples (n ¼ 2978) were analysed between January 2008 and December 2009. Fifteen antibiotics of the macrolide and aminoglycoside groups (clindamycin, eritromycin, lincomycin, tylmicosin, tylosin, amikacin, apramycin, dihydrostreptomycin, gentamycin, higromycin, kanamycin, neomycin, spectinomycin, streptomycin, tobramycin) were determined by a microbiological screening method (FAST) and confirmed/quantified using liquid chromatography (LC-MS/MS and UPLC-MS/MS). In 2008, 1459 samples were analysed by a screening test and liquid chromatography with only one sample (0.07%) exceeded Brazilian legislation limits (4MRL). In 2009, 1519 samples were analysed and none exceeding Brazilian legislation limits (4MRL). The slaughterhouses of 16 states were monitored during the year of 2008, and 18 states were monitored in 2009, being the major producing states most sampled by the PNCRC.
Calibration transfer is commonly used for spectra obtained in different spectrometers or other co... more Calibration transfer is commonly used for spectra obtained in different spectrometers or other conditions. This paper proposed the use of calibration transfer between spectra recorded for the same samples in different physical forms. A new method was developed for the direct determination of nevirapine in solid pharmaceutical formulations based on diffuse reflectance near infrared spectroscopy (NIRS) and partial least squares (PLS). This method was developed with 50 powder mixtures and then, successfully extended to the quantification in intact tablets by using calibration transfer with double window piecewise direct standardization (DWPDS). This chemometric strategy provided good results with a small number of tablet transfer samples, only seven, prepared out of the narrow range of active principle ingredients (API) content around the nominal value of the formulation (100%). The method was fully validated in the working range of 83.0-113.9% of nevirapine and the use of DWPDS allowed to significantly decreasing the root mean square error of prediction (RMSEP) from 4.8% (tablets predicted by a model built with only powder samples) to 2.6%. The range of relative errors decreased from À 5.1/8.7% to À 4.6/3.3%. Considering that the amount of raw materials demanded for preparing tablets is up to ten times higher than for powder mixtures, this type of application is of particular interest in pharmaceutical analysis. In the context of process analytical technology (PAT), the use of the same multivariate model in different steps of the production is very advantageous, saving time and labor.
This paper proposed a new screening method for the simultaneous detection of five common adultera... more This paper proposed a new screening method for the simultaneous detection of five common adulterants in raw cow milk by using attenuated total reflectance (ATR) mid infrared spectroscopy and multivariate supervised classification (partial least squares discrimination analysis -PLSDA). The method was able to detect the presence of the adulterants water, starch, sodium citrate, formaldehyde and sucrose in milk samples containing from one up to five of these analytes, in the range of 0.5-10% w/v. A multivariate qualitative validation was performed, estimating specific figures of merit, such as false positive and false negative rates, selectivity, specificity and efficiency rates, accordance and concordance. The proposed method does not need any sample pretreatment, requires a small amount of sample (30 lL), is fast and simple, being suitable for the control of raw milk in a dairy industry or for the quality inspection of commercialized milk.
This paper proposed a novel methodology for the quantification of an artificial dye, sunset yello... more This paper proposed a novel methodology for the quantification of an artificial dye, sunset yellow (SY), in soft beverages, using image analysis (RGB histograms) and partial least squares regression. The developed method presented many advantages if compared with alternative methodologies, such as HPLC and UV/ VIS spectrophotometry. It was faster, did not require sample pretreatment steps or any kind of solvents and reagents, and used a low cost equipment, a commercial flatbed scanner. This method was able to quantify SY in isotonic drinks and orange sodas, in the range of 7.8-39.7 mg L À1 , with relative prediction errors lower than 10%. A multivariate validation was also performed according to the Brazilian and international guidelines. Linearity, accuracy, sensitivity, bias, prediction uncertainty and a recently proposed tool, the b-expectation tolerance intervals, were estimated. The application of digital images in food analysis is very promising, opening the possibility for automation.
Densidade (PEBD) e embalagens a vácuo sobre a cor, a qualidade físico-química e microbiológica do... more Densidade (PEBD) e embalagens a vácuo sobre a cor, a qualidade físico-química e microbiológica do queijo Minas frescal. Foram avaliados 10 queijos provenientes de 5 produtores artesanais da cidade de Belo Horizonte, adquiridos 2 dias após a fabricação. Os queijos foram divididos em dois grupos, cada qual com 15 unidades (três pedaços de cinco queijos), e acondicionados em geladeira a temperatura de 6 ºC até o momento dos testes. As análises de pH, teor de umidade, teor de gordura, microbiológicas e o estudo da cor foram feitos nos dias 0, 10 e 20, tanto da parte interna, quanto da parte externa do produto. O uso de ferramentas quimiométricas, como o Image Principal Componente Analysis (PCA de imagens), permitiu evidenciar alterações de cor das amostras no período de observação e correlacioná-las com os dois tipos de embalagens utilizados e com os valores obtidos nas análises físico-químicas. Os resultados apontaram que as características das embalagens relacionadas à permeabilidade a gases e vapor d'água propiciaram alterações físico-químicas e microbiológicas nas amostras, resultando em diferentes tonalidades de amarelo perfeitamente evidenciadas pelo PCA, sendo que a embalagem a vácuo se demonstrou mais eficaz na conservação das propriedades avaliadas. A contaminação microbiológica das amostras ressaltou a importância das boas práticas de fabricação (BPF) na qualidade do queijo Minas frescal. PALAVRAS-CHAVE: PCA. Queijo Minas Frescal. Cor. Embalagem
Premi Õ Test, a microbial inhibition test for the screening of antimicrobial residues, was valida... more Premi Õ Test, a microbial inhibition test for the screening of antimicrobial residues, was validated according to the criteria established by Decision 2002/657/EC. Sensitivity, detection capability (CC), specificity, selectivity, robustness and applicability were evaluated. The methodology involves the technique of solvent extraction, which increases the detection capability of the test for a wider range of antibiotics. The following CC values in poultry muscle were found: penicillin G 12.5 mg kg À1 , total sulfonamides 75 mg kg À1 , erythromycin 75 mg kg À1 and lincomycin 50 mg kg À1 . The detection capability of chlortetracycline was equal to its maximum residue limit (100 mg kg À1 ) and the method did not detect gentamicin (1000 mg kg À1 ), for which no MRL is established in poultry muscle. Specificity evaluated in relation to different analytes and matrices did not detect any interferences in the tests results; whilst the robustness showed that the pH neutralisation point of the extract affects the analytical results and the kits' performance. Only the screening of tetracyclines requires the analysis of extracts without pH neutralisation. The results of the validation process showed that this method is acceptable for screening -lactam, sulfonamide and macrolide antimicrobial groups in the National Residues and Contaminants Control Programme (PNCRC), and that for this it is fit for purpose.
Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS] is... more Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS] is used to obtain fingerprints of aqueous-methanolic extracts of two types of olive oils, extra virgin (EV) and ordinary (OR), as well as of samples of EV olive oil adulterated by the addition of OR olive oil and other edible oils: corn (CO), sunflower (SF), soybean (SO) and canola (CA). The MS data is treated by the partial least squares discriminant analysis (PLS-DA) protocol aiming at discriminating the abovementioned classes formed by the genuine olive oils, EV (1) and OR , as well as the EV adulterated samples, i.e. EV/SO , EV/CO (4), EV/SF (5), EV/CA (6) and EV/OR . The PLS-DA model employed is built with 190 and 70 samples for the training and test sets, respectively. For all classes (1-7), EV and OR olive oils as well as the adulterated samples (in a proportion varying from 0.5 to 20.0% w/w) are properly classified. The developed methodology required no ions identification and demonstrated to be fast, as each measurement lasted about 3 min including the extraction step and MS analysis, and reliable, because high sensitivities (rate of true positives) and specificities (rate of true negatives) were achieved. Finally, it can be envisaged that this approach has potential to be applied in quality control of EV olive oils.
This paper proposed and validated robust diffuse reflectance near-infrared methods for the direct... more This paper proposed and validated robust diffuse reflectance near-infrared methods for the direct determination of fat and moisture in cow mozzarella cheeses using partial least squares regression. They were developed under the realistic conditions of routine analysis in a state laboratory of quality inspection control and were used for analyzing a great variety of mozzarella samples manufactured by different manufacturing procedures and originating from the whole state of Minas Gerais, Brazil (more than 100 different producers). A robust methodology was implemented, including the detection of outliers and the harmonization of the multivariate concepts with the traditional univariate guidelines. The models were constructed in the ranges from 38.7 to 58.0 % w/w on dry basis for fat and from 41.5 to 55.1 % w/w for moisture, providing root mean square errors of prediction of 2.1 and 0.9 %, respectively. Both methods were validated through the estimation of figures of merit, such as linearity, trueness, precision, analytical sensitivity, ruggedness, bias, and residual prediction deviation. Once the methods were adopted, their performances were monitored for approximately 1 year through control charts and were considered satisfactorily stable with prediction errors within the established limits. Beyond these specific methods, it was also pursued to present a complete methodology for multivariate analytical validation, an important aspect for the implementation of near-infrared spectroscopy methods in the routine of food quality inspection.
Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS] is... more Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS] is used to obtain fingerprints of aqueous-methanolic extracts of two types of olive oils, extra virgin (EV) and ordinary (OR), as well as of samples of EV olive oil adulterated by the addition of OR olive oil and other edible oils: corn (CO), sunflower (SF), soybean (SO) and canola (CA). The MS data is treated by the partial least squares discriminant analysis (PLS-DA) protocol aiming at discriminating the abovementioned classes formed by the genuine olive oils, EV (1) and OR , as well as the EV adulterated samples, i.e. EV/SO , EV/CO (4), EV/SF (5), EV/CA (6) and EV/OR . The PLS-DA model employed is built with 190 and 70 samples for the training and test sets, respectively. For all classes (1-7), EV and OR olive oils as well as the adulterated samples (in a proportion varying from 0.5 to 20.0% w/w) are properly classified. The developed methodology required no ions identification and demonstrated to be fast, as each measurement lasted about 3 min including the extraction step and MS analysis, and reliable, because high sensitivities (rate of true positives) and specificities (rate of true negatives) were achieved. Finally, it can be envisaged that this approach has potential to be applied in quality control of EV olive oils.
This paper proposed and validated robust diffuse reflectance near-infrared methods for the direct... more This paper proposed and validated robust diffuse reflectance near-infrared methods for the direct determination of fat and moisture in cow mozzarella cheeses using partial least squares regression. They were developed under the realistic conditions of routine analysis in a state laboratory of quality inspection control and were used for analyzing a great variety of mozzarella samples manufactured by different manufacturing procedures and originating from the whole state of Minas Gerais, Brazil (more than 100 different producers). A robust methodology was implemented, including the detection of outliers and the harmonization of the multivariate concepts with the traditional univariate guidelines. The models were constructed in the ranges from 38.7 to 58.0 % w/w on dry basis for fat and from 41.5 to 55.1 % w/w for moisture, providing root mean square errors of prediction of 2.1 and 0.9 %, respectively. Both methods were validated through the estimation of figures of merit, such as linearity, trueness, precision, analytical sensitivity, ruggedness, bias, and residual prediction deviation. Once the methods were adopted, their performances were monitored for approximately 1 year through control charts and were considered satisfactorily stable with prediction errors within the established limits. Beyond these specific methods, it was also pursued to present a complete methodology for multivariate analytical validation, an important aspect for the implementation of near-infrared spectroscopy methods in the routine of food quality inspection.
Recebido em 7/2/13; aceito em 29/4/13; publicado na web em 1/7/13 IMPLEMENTATION OF A ROBUST METH... more Recebido em 7/2/13; aceito em 29/4/13; publicado na web em 1/7/13 IMPLEMENTATION OF A ROBUST METHOD FOR QUALITY INSPECTION CONTROL OF ARTISANAL MINAS CHEESE. A MULTIVARIATE METROLOGICAL APPROACH. This study developed and validated a method for moisture determination in artisanal Minas cheese, using near-infrared spectroscopy and partial-least-squares. The model robustness was assured by broad sample diversity, real conditions of routine analysis, variable selection, outlier detection and analytical validation. The model was built from 28.5-55.5% w/w, with a root-mean-square-error-of-prediction of 1.6%. After its adoption, the method stability was confirmed over a period of two years through the development of a control chart. Besides this specific method, the present study sought to provide an example multivariate metrological methodology with potential for application in several areas, including new aspects, such as more stringent evaluation of the linearity of multivariate methods.
This paper proposed a novel methodology for the quantification of an artificial dye, sunset yello... more This paper proposed a novel methodology for the quantification of an artificial dye, sunset yellow (SY), in soft beverages, using image analysis (RGB histograms) and partial least squares regression. The developed method presented many advantages if compared with alternative methodologies, such as HPLC and UV/ VIS spectrophotometry. It was faster, did not require sample pretreatment steps or any kind of solvents and reagents, and used a low cost equipment, a commercial flatbed scanner. This method was able to quantify SY in isotonic drinks and orange sodas, in the range of 7.8-39.7 mg L À1 , with relative prediction errors lower than 10%. A multivariate validation was also performed according to the Brazilian and international guidelines. Linearity, accuracy, sensitivity, bias, prediction uncertainty and a recently proposed tool, the b-expectation tolerance intervals, were estimated. The application of digital images in food analysis is very promising, opening the possibility for automation.
This paper proposed a new screening method for the simultaneous detection of five common adultera... more This paper proposed a new screening method for the simultaneous detection of five common adulterants in raw cow milk by using attenuated total reflectance (ATR) mid infrared spectroscopy and multivariate supervised classification (partial least squares discrimination analysis -PLSDA). The method was able to detect the presence of the adulterants water, starch, sodium citrate, formaldehyde and sucrose in milk samples containing from one up to five of these analytes, in the range of 0.5-10% w/v. A multivariate qualitative validation was performed, estimating specific figures of merit, such as false positive and false negative rates, selectivity, specificity and efficiency rates, accordance and concordance. The proposed method does not need any sample pretreatment, requires a small amount of sample (30 lL), is fast and simple, being suitable for the control of raw milk in a dairy industry or for the quality inspection of commercialized milk.
Brazil is one of the most important countries as a producer and exporter of cattle and poultry. I... more Brazil is one of the most important countries as a producer and exporter of cattle and poultry. In 2009 cattle accounted for 30% of the export market and 41.4% for poultry meat. The Brazilian National Residues and Contaminants Control Plan (PNCRC) follows the guidelines set by the Codex Alimentarius Commission and checks compliance maximum residue limits (MRLs) to ensure the quality of these commodities. Kidney samples (n ¼ 2978) were analysed between January 2008 and December 2009. Fifteen antibiotics of the macrolide and aminoglycoside groups (clindamycin, eritromycin, lincomycin, tylmicosin, tylosin, amikacin, apramycin, dihydrostreptomycin, gentamycin, higromycin, kanamycin, neomycin, spectinomycin, streptomycin, tobramycin) were determined by a microbiological screening method (FAST) and confirmed/quantified using liquid chromatography (LC-MS/MS and UPLC-MS/MS). In 2008, 1459 samples were analysed by a screening test and liquid chromatography with only one sample (0.07%) exceeded Brazilian legislation limits (4MRL). In 2009, 1519 samples were analysed and none exceeding Brazilian legislation limits (4MRL). The slaughterhouses of 16 states were monitored during the year of 2008, and 18 states were monitored in 2009, being the major producing states most sampled by the PNCRC.
Calibration transfer is commonly used for spectra obtained in different spectrometers or other co... more Calibration transfer is commonly used for spectra obtained in different spectrometers or other conditions. This paper proposed the use of calibration transfer between spectra recorded for the same samples in different physical forms. A new method was developed for the direct determination of nevirapine in solid pharmaceutical formulations based on diffuse reflectance near infrared spectroscopy (NIRS) and partial least squares (PLS). This method was developed with 50 powder mixtures and then, successfully extended to the quantification in intact tablets by using calibration transfer with double window piecewise direct standardization (DWPDS). This chemometric strategy provided good results with a small number of tablet transfer samples, only seven, prepared out of the narrow range of active principle ingredients (API) content around the nominal value of the formulation (100%). The method was fully validated in the working range of 83.0-113.9% of nevirapine and the use of DWPDS allowed to significantly decreasing the root mean square error of prediction (RMSEP) from 4.8% (tablets predicted by a model built with only powder samples) to 2.6%. The range of relative errors decreased from À 5.1/8.7% to À 4.6/3.3%. Considering that the amount of raw materials demanded for preparing tablets is up to ten times higher than for powder mixtures, this type of application is of particular interest in pharmaceutical analysis. In the context of process analytical technology (PAT), the use of the same multivariate model in different steps of the production is very advantageous, saving time and labor.
This paper proposed a new screening method for the simultaneous detection of five common adultera... more This paper proposed a new screening method for the simultaneous detection of five common adulterants in raw cow milk by using attenuated total reflectance (ATR) mid infrared spectroscopy and multivariate supervised classification (partial least squares discrimination analysis -PLSDA). The method was able to detect the presence of the adulterants water, starch, sodium citrate, formaldehyde and sucrose in milk samples containing from one up to five of these analytes, in the range of 0.5-10% w/v. A multivariate qualitative validation was performed, estimating specific figures of merit, such as false positive and false negative rates, selectivity, specificity and efficiency rates, accordance and concordance. The proposed method does not need any sample pretreatment, requires a small amount of sample (30 lL), is fast and simple, being suitable for the control of raw milk in a dairy industry or for the quality inspection of commercialized milk.
This paper proposed a novel methodology for the quantification of an artificial dye, sunset yello... more This paper proposed a novel methodology for the quantification of an artificial dye, sunset yellow (SY), in soft beverages, using image analysis (RGB histograms) and partial least squares regression. The developed method presented many advantages if compared with alternative methodologies, such as HPLC and UV/ VIS spectrophotometry. It was faster, did not require sample pretreatment steps or any kind of solvents and reagents, and used a low cost equipment, a commercial flatbed scanner. This method was able to quantify SY in isotonic drinks and orange sodas, in the range of 7.8-39.7 mg L À1 , with relative prediction errors lower than 10%. A multivariate validation was also performed according to the Brazilian and international guidelines. Linearity, accuracy, sensitivity, bias, prediction uncertainty and a recently proposed tool, the b-expectation tolerance intervals, were estimated. The application of digital images in food analysis is very promising, opening the possibility for automation.
Densidade (PEBD) e embalagens a vácuo sobre a cor, a qualidade físico-química e microbiológica do... more Densidade (PEBD) e embalagens a vácuo sobre a cor, a qualidade físico-química e microbiológica do queijo Minas frescal. Foram avaliados 10 queijos provenientes de 5 produtores artesanais da cidade de Belo Horizonte, adquiridos 2 dias após a fabricação. Os queijos foram divididos em dois grupos, cada qual com 15 unidades (três pedaços de cinco queijos), e acondicionados em geladeira a temperatura de 6 ºC até o momento dos testes. As análises de pH, teor de umidade, teor de gordura, microbiológicas e o estudo da cor foram feitos nos dias 0, 10 e 20, tanto da parte interna, quanto da parte externa do produto. O uso de ferramentas quimiométricas, como o Image Principal Componente Analysis (PCA de imagens), permitiu evidenciar alterações de cor das amostras no período de observação e correlacioná-las com os dois tipos de embalagens utilizados e com os valores obtidos nas análises físico-químicas. Os resultados apontaram que as características das embalagens relacionadas à permeabilidade a gases e vapor d'água propiciaram alterações físico-químicas e microbiológicas nas amostras, resultando em diferentes tonalidades de amarelo perfeitamente evidenciadas pelo PCA, sendo que a embalagem a vácuo se demonstrou mais eficaz na conservação das propriedades avaliadas. A contaminação microbiológica das amostras ressaltou a importância das boas práticas de fabricação (BPF) na qualidade do queijo Minas frescal. PALAVRAS-CHAVE: PCA. Queijo Minas Frescal. Cor. Embalagem
Premi Õ Test, a microbial inhibition test for the screening of antimicrobial residues, was valida... more Premi Õ Test, a microbial inhibition test for the screening of antimicrobial residues, was validated according to the criteria established by Decision 2002/657/EC. Sensitivity, detection capability (CC), specificity, selectivity, robustness and applicability were evaluated. The methodology involves the technique of solvent extraction, which increases the detection capability of the test for a wider range of antibiotics. The following CC values in poultry muscle were found: penicillin G 12.5 mg kg À1 , total sulfonamides 75 mg kg À1 , erythromycin 75 mg kg À1 and lincomycin 50 mg kg À1 . The detection capability of chlortetracycline was equal to its maximum residue limit (100 mg kg À1 ) and the method did not detect gentamicin (1000 mg kg À1 ), for which no MRL is established in poultry muscle. Specificity evaluated in relation to different analytes and matrices did not detect any interferences in the tests results; whilst the robustness showed that the pH neutralisation point of the extract affects the analytical results and the kits' performance. Only the screening of tetracyclines requires the analysis of extracts without pH neutralisation. The results of the validation process showed that this method is acceptable for screening -lactam, sulfonamide and macrolide antimicrobial groups in the National Residues and Contaminants Control Programme (PNCRC), and that for this it is fit for purpose.
Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS] is... more Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS] is used to obtain fingerprints of aqueous-methanolic extracts of two types of olive oils, extra virgin (EV) and ordinary (OR), as well as of samples of EV olive oil adulterated by the addition of OR olive oil and other edible oils: corn (CO), sunflower (SF), soybean (SO) and canola (CA). The MS data is treated by the partial least squares discriminant analysis (PLS-DA) protocol aiming at discriminating the abovementioned classes formed by the genuine olive oils, EV (1) and OR , as well as the EV adulterated samples, i.e. EV/SO , EV/CO (4), EV/SF (5), EV/CA (6) and EV/OR . The PLS-DA model employed is built with 190 and 70 samples for the training and test sets, respectively. For all classes (1-7), EV and OR olive oils as well as the adulterated samples (in a proportion varying from 0.5 to 20.0% w/w) are properly classified. The developed methodology required no ions identification and demonstrated to be fast, as each measurement lasted about 3 min including the extraction step and MS analysis, and reliable, because high sensitivities (rate of true positives) and specificities (rate of true negatives) were achieved. Finally, it can be envisaged that this approach has potential to be applied in quality control of EV olive oils.
This paper proposed and validated robust diffuse reflectance near-infrared methods for the direct... more This paper proposed and validated robust diffuse reflectance near-infrared methods for the direct determination of fat and moisture in cow mozzarella cheeses using partial least squares regression. They were developed under the realistic conditions of routine analysis in a state laboratory of quality inspection control and were used for analyzing a great variety of mozzarella samples manufactured by different manufacturing procedures and originating from the whole state of Minas Gerais, Brazil (more than 100 different producers). A robust methodology was implemented, including the detection of outliers and the harmonization of the multivariate concepts with the traditional univariate guidelines. The models were constructed in the ranges from 38.7 to 58.0 % w/w on dry basis for fat and from 41.5 to 55.1 % w/w for moisture, providing root mean square errors of prediction of 2.1 and 0.9 %, respectively. Both methods were validated through the estimation of figures of merit, such as linearity, trueness, precision, analytical sensitivity, ruggedness, bias, and residual prediction deviation. Once the methods were adopted, their performances were monitored for approximately 1 year through control charts and were considered satisfactorily stable with prediction errors within the established limits. Beyond these specific methods, it was also pursued to present a complete methodology for multivariate analytical validation, an important aspect for the implementation of near-infrared spectroscopy methods in the routine of food quality inspection.
Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS] is... more Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS] is used to obtain fingerprints of aqueous-methanolic extracts of two types of olive oils, extra virgin (EV) and ordinary (OR), as well as of samples of EV olive oil adulterated by the addition of OR olive oil and other edible oils: corn (CO), sunflower (SF), soybean (SO) and canola (CA). The MS data is treated by the partial least squares discriminant analysis (PLS-DA) protocol aiming at discriminating the abovementioned classes formed by the genuine olive oils, EV (1) and OR , as well as the EV adulterated samples, i.e. EV/SO , EV/CO (4), EV/SF (5), EV/CA (6) and EV/OR . The PLS-DA model employed is built with 190 and 70 samples for the training and test sets, respectively. For all classes (1-7), EV and OR olive oils as well as the adulterated samples (in a proportion varying from 0.5 to 20.0% w/w) are properly classified. The developed methodology required no ions identification and demonstrated to be fast, as each measurement lasted about 3 min including the extraction step and MS analysis, and reliable, because high sensitivities (rate of true positives) and specificities (rate of true negatives) were achieved. Finally, it can be envisaged that this approach has potential to be applied in quality control of EV olive oils.
This paper proposed and validated robust diffuse reflectance near-infrared methods for the direct... more This paper proposed and validated robust diffuse reflectance near-infrared methods for the direct determination of fat and moisture in cow mozzarella cheeses using partial least squares regression. They were developed under the realistic conditions of routine analysis in a state laboratory of quality inspection control and were used for analyzing a great variety of mozzarella samples manufactured by different manufacturing procedures and originating from the whole state of Minas Gerais, Brazil (more than 100 different producers). A robust methodology was implemented, including the detection of outliers and the harmonization of the multivariate concepts with the traditional univariate guidelines. The models were constructed in the ranges from 38.7 to 58.0 % w/w on dry basis for fat and from 41.5 to 55.1 % w/w for moisture, providing root mean square errors of prediction of 2.1 and 0.9 %, respectively. Both methods were validated through the estimation of figures of merit, such as linearity, trueness, precision, analytical sensitivity, ruggedness, bias, and residual prediction deviation. Once the methods were adopted, their performances were monitored for approximately 1 year through control charts and were considered satisfactorily stable with prediction errors within the established limits. Beyond these specific methods, it was also pursued to present a complete methodology for multivariate analytical validation, an important aspect for the implementation of near-infrared spectroscopy methods in the routine of food quality inspection.
Recebido em 7/2/13; aceito em 29/4/13; publicado na web em 1/7/13 IMPLEMENTATION OF A ROBUST METH... more Recebido em 7/2/13; aceito em 29/4/13; publicado na web em 1/7/13 IMPLEMENTATION OF A ROBUST METHOD FOR QUALITY INSPECTION CONTROL OF ARTISANAL MINAS CHEESE. A MULTIVARIATE METROLOGICAL APPROACH. This study developed and validated a method for moisture determination in artisanal Minas cheese, using near-infrared spectroscopy and partial-least-squares. The model robustness was assured by broad sample diversity, real conditions of routine analysis, variable selection, outlier detection and analytical validation. The model was built from 28.5-55.5% w/w, with a root-mean-square-error-of-prediction of 1.6%. After its adoption, the method stability was confirmed over a period of two years through the development of a control chart. Besides this specific method, the present study sought to provide an example multivariate metrological methodology with potential for application in several areas, including new aspects, such as more stringent evaluation of the linearity of multivariate methods.
This paper proposed a novel methodology for the quantification of an artificial dye, sunset yello... more This paper proposed a novel methodology for the quantification of an artificial dye, sunset yellow (SY), in soft beverages, using image analysis (RGB histograms) and partial least squares regression. The developed method presented many advantages if compared with alternative methodologies, such as HPLC and UV/ VIS spectrophotometry. It was faster, did not require sample pretreatment steps or any kind of solvents and reagents, and used a low cost equipment, a commercial flatbed scanner. This method was able to quantify SY in isotonic drinks and orange sodas, in the range of 7.8-39.7 mg L À1 , with relative prediction errors lower than 10%. A multivariate validation was also performed according to the Brazilian and international guidelines. Linearity, accuracy, sensitivity, bias, prediction uncertainty and a recently proposed tool, the b-expectation tolerance intervals, were estimated. The application of digital images in food analysis is very promising, opening the possibility for automation.
This paper proposed a new screening method for the simultaneous detection of five common adultera... more This paper proposed a new screening method for the simultaneous detection of five common adulterants in raw cow milk by using attenuated total reflectance (ATR) mid infrared spectroscopy and multivariate supervised classification (partial least squares discrimination analysis -PLSDA). The method was able to detect the presence of the adulterants water, starch, sodium citrate, formaldehyde and sucrose in milk samples containing from one up to five of these analytes, in the range of 0.5-10% w/v. A multivariate qualitative validation was performed, estimating specific figures of merit, such as false positive and false negative rates, selectivity, specificity and efficiency rates, accordance and concordance. The proposed method does not need any sample pretreatment, requires a small amount of sample (30 lL), is fast and simple, being suitable for the control of raw milk in a dairy industry or for the quality inspection of commercialized milk.
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