The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Anne Thierry - One of the best experts on this subject based on the ideXlab platform.
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Identification of a secreted lipolytic esterase in Propionibacterium freudenreichii
2011Co-Authors: Julien Dherbecourt, Hélène Falentin, Julien Jardin, Frédérique Barloy-hubler, Anne ThierryAbstract:Lipolysis plays an important role in the formation of Cheese Flavor. In Emmental Cheese, the main part of lipolysis has been associated with the presence of Propionibacterium freudenreichii, a species used as a ripening culture. Our aim was to identify the most probable lipolytic esterase(s) involved in Cheese lipolysis by P. freudenreichii. Since Cheese lipolysis mainly occurs during P. freudenreichii growth, we hypothesized that P. freudenreichii possesses secreted lipolytic esterase(s). For 12 putative esterase genes previously identified from the genome of P. freudenreichii CIRM1, the level of expression was quantified by real-time reverse transcriptase (RT)-PCR, and the subcellular localization of esterases was predicted in silico. The esterase activity in extracellular and intracellular extracts of P. freudenreichii was characterized by zymography, and the extracellular esterases were identified by mass spectrometry. Finally, the best candidate was overexpressed in the same strain. All of the 12 genes encoding putative esterases were expressed. Esterase PF#279 was predicted to be secreted in the medium, PF#774 to be surface exposed, and the 10 remaining putative esterases to be intracellular. Zymography revealed that esterase activities in culture supernatant differed from the ones detected in intracellular extracts. PF#279 was identified as the sole esterase present in culture supernatant. Transformed P. freudenreichii CIRM1 clones overexpressing PF#279 showed 5 to 8 times more lipolytic activity on milk fat than the wild-type strain. Combining in silico, biochemical, and genetic approaches, we showed that PF#279 is the sole secreted esterase in P. freudenreichii and is active on milk fat. Therefore, it is likely a key component in Cheese lipolysis by P. freudenreichii.
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Identification of a secreted lipolytic esterase in Propionibacterium freudenreichii, a ripening process bacterium involved in emmental Cheese lipolysis.
Applied and Environmental Microbiology, 2010Co-Authors: Julien Dherbecourt, Julien Jardin, Frédérique Barloy-hubler, M.-b. Maillard, F. Baglinière, Anne ThierryAbstract:Lipolysis plays an important role in the formation of Cheese Flavor. In Emmental Cheese, the main part of lipolysis has been associated with the presence of Propionibacterium freudenreichii, a species used as a ripening culture. Our aim was to identify the most probable lipolytic esterase(s) involved in Cheese lipolysis by P. freudenreichii. Since Cheese lipolysis mainly occurs during P. freudenreichii growth, we hypothesized that P. freudenreichii possesses secreted lipolytic esterase(s). For 12 putative esterase genes previously identified from the genome of P. freudenreichii CIRM1, the level of expression was quantified by real-time reverse transcriptase (RT)-PCR, and the subcellular localization of esterases was predicted in silico. The esterase activity in extracellular and intracellular extracts of P. freudenreichii was characterized by zymography, and the extracellular esterases were identified by mass spectrometry. Finally, the best candidate was overexpressed in the same strain. All of the 12 genes encoding putative esterases were expressed. Esterase PF#279 was predicted to be secreted in the medium, PF#774 to be surface exposed, and the 10 remaining putative esterases to be intracellular. Zymography revealed that esterase activities in culture supernatant differed from the ones detected in intracellular extracts. PF#279 was identified as the sole esterase present in culture supernatant. Transformed P. freudenreichii CIRM1 clones overexpressing PF#279 showed 5 to 8 times more lipolytic activity on milk fat than the wild-type strain. Combining in silico, biochemical, and genetic approaches, we showed that PF#279 is the sole secreted esterase in P. freudenreichii and is active on milk fat. Therefore, it is likely a key component in Cheese lipolysis by P. freudenreichii.
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the addition of propionibacterium freudenreichii to raclette Cheese induces biochemical changes and enhances Flavor development
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Anne Thierry, Mariebernadette Maillard, Pascal Bonnarme, Edmond RousselAbstract:Two mixtures of Propionibacterium freudenreichii commercial strains were tested as adjunct cultures in pasteurized milk Raclette Cheese to investigate the ability of propionibacteria (PAB) to enhance Flavor development. Cheese Flavor was assessed by a trained sensory panel, and levels of free amino acids, free fatty acids, and volatile compounds were determined. The PAB level showed a 1.4 log increase within the ripening period (12 weeks at 11 degrees C). Eye formation, which was not desired, was not observed in PAB Cheeses. PAB fermented lactate to acetate and propionate and produced fatty acids by lipolysis, branched chain volatile compounds derived from isoleucine and leucine catabolism and some esters. One of the experimental Cheeses received the highest scores for odor and Flavor intensity and was characterized by higher frequencies of detection for some minor notes ("propionic"and "whey" odor, "sweet" taste). PAB can therefore be considered as potential adjunct cultures to enhance or modify Cheese Flavor development.
Mary Anne Drake - One of the best experts on this subject based on the ideXlab platform.
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Sensory and chemical properties of Gouda Cheese
Journal of Dairy Science, 2017Co-Authors: Y Jo, A Ameerally, D.m. Benoist, Mary Anne DrakeAbstract:Gouda Cheese is a washed-curd Cheese that is traditionally produced from bovine milk and brined before ripening for 1 to 20 mo. In response to domestic and international demand, US production of Gouda Cheese has more than doubled in recent years. An understanding of the chemical and sensory properties of Gouda Cheese can help manufacturers create desirable products. The objective of this study was to determine the chemical and sensory properties of Gouda Cheeses. Commercial Gouda Cheeses (n = 36; 3 mo to 5 yr; domestic and international) were obtained in duplicate lots. Volatile compounds were extracted by solid-phase microextraction and analyzed by gas chromatography–olfactometry and gas chromatography–mass spectrometry. Composition analyses included pH, proximate analysis, salt content, organic acid analysis by HPLC, and color. Flavor and texture properties were determined by descriptive sensory analysis. Focus groups were conducted to document US consumer perception followed by consumer acceptance testing (n = 149) with selected Cheeses. Ninety aroma-active compounds in Gouda Cheeses were detected by solid-phase microextraction/gas chromatography–olfactometry. Key aroma-active volatile compounds included diacetyl, 2- and 3-methylbutanal, 2-methylpropanal, methional, ethyl butyrate, acetic acid, butyric acid, homofuraneol, δ-decalactone, and 2-isobutyl-3-methoxypyrazine. Aged Cheeses had higher organic acid concentrations, higher fat and salt contents, and lower moisture content than younger Cheeses. Younger Cheeses were characterized by milky, whey, sour aromatic, and diacetyl Flavors, whereas aged Cheeses were characterized by fruity, caramel, malty/nutty, and brothy Flavors. International Cheeses were differentiated by the presence of low intensities of cowy/barny and grassy Flavors. Younger Cheeses were characterized by higher intensities of smoothness and mouth coating, whereas aged Cheeses were characterized by higher intensities of fracture and firmness. American consumers used Gouda Cheese in numerous applications and stated that packaging appeal, quality, and age were more important than country of origin or nutrition when purchasing Gouda Cheeses. Young and medium US Cheeses ≤6 mo were most liked by US consumers. Three distinct consumer segments were identified with distinct preferences for Cheese Flavor and texture. Findings from this study establish key differences in Gouda Cheese regarding age and origin and identify US consumer desires for this Cheese category.
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Effect of sodium, potassium, magnesium, and calcium salt cations on pH, proteolysis, organic acids, and microbial populations during storage of full-fat Cheddar Cheese.
Journal of dairy science, 2014Co-Authors: Donald J. Mcmahon, Balasubramanian Ganesan, Mary Anne Drake, M R Arnold, J Steele, N. Ana Y. Farkye, Craig J. Oberg, Lynn V. Moyes, Jeffery R BroadbentAbstract:Sodium reduction in Cheese can assist in reducing overall dietary Na intake, yet saltiness is an important aspect of Cheese Flavor. Our objective was to evaluate the effect of partial substitution of Na with K on survival of lactic acid bacteria (LAB) and nonstarter LAB (NSLAB), pH, organic acid production, and extent of proteolysis as water-soluble nitrogen (WSN) and protein profiles using urea-PAGE, in Cheddar Cheese during 9mo of storage. Seven Cheddar Cheeses with molar salt contents equivalent to 1.7% salt but with different ratios of Na, K, Ca, and Mg cations were manufactured as well as a low-salt Cheese with 0.7% salt. The 1.7% salt Cheeses had a mean composition of 352g of moisture/kg, 259g of protein/kg and 50% fat-on-dry-basis, and 17.5g of salt/kg (measured as Cl(-)). After salting, a faster initial decrease in Cheese pH occurred with low salt or K substitution and it remained lower throughout storage. No difference in intact casein levels or percentage WSN levels between the various Cheeses was observed, with the percentage WSN increasing from 5% at d 1 to 25% at 9mo. A greater decrease in intact αs1-casein than β-casein was detected, and the ratio of αs1-casein (f121-199) to αs1-casein could be used as an index of ripening. Typical changes in bacteria microflora occurred during storage, with lactococci decreasing gradually and NSLAB increasing. Lowering the Na content, even with K replacement, extended the crossover time when NSLAB became dominant. The crossover time was 4.5mo for the control Cheese and was delayed to 5.2, 6.0, 6.1, and 6.2mo for Cheeses with 10, 25, 50, and 75% K substitution. Including 10% Mg or Ca, along with 40% K, further increased crossover time, whereas the longest crossover time (7.3mo) was for low-salt Cheese. By 9mo, NSLAB levels in all Cheeses had increased from initial levels of ≤10(2) to approximately 10(6)cfu/g. Lactococci remained at 10(6) cfu/g in the low-salt Cheese even after 9mo of storage. The propionic acid concentration in the Cheese increased when NSLAB numbers were high. Few other trends in organic acid concentration were observed as a function of Na content.
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EVALUATION OF KEY Flavor COMPOUNDS IN REDUCED- AND FULL-FAT CHEDDAR CheeseS USING SENSORY STUDIES ON MODEL SYSTEMS: KEY Flavor COMPOUNDS IN CHEDDAR Cheese
Journal of Sensory Studies, 2011Co-Authors: M.k. Kim, S L Drake, Mary Anne DrakeAbstract:Recent Flavor chemistry studies have identified Flavor compounds at different concentrations in full- and low-fat Cheddar Cheeses. The specific Flavor contributions of these compounds in full- and low-fat Cheese matrices have not been established. The purpose of this study was to evaluate the sensory response of Cheddar Flavor compounds in model full-fat and 75% reduced-fat Cheeses. Odor activity values (OAVs) for each compound in full- and reduced-fat Cheeses were calculated. Each compound was then added to model Cheeses created from 3-week-old full- and reduced-fat Cheddar Cheeses. A trained sensory panel (n = 8) evaluated the sensory properties of the Cheese models. The final combination of compounds was incorporated into reduced-fat Cheese models, and consumers (n = 85) evaluated perceived-aged Cheddar Cheese aroma. Based on OAVs and perception of the individual compounds in Cheese models, 12 key Flavor compounds were identified. Target ideal concentrations of specific Cheese Flavor compounds in 75% reduced-fat Cheese were determined. According to consumers, the perceived aged Cheddar Cheese aroma intensity of reduced-fat model Cheese with these added compounds was not different (P > 0.05) from the perceived Cheddar Cheese aroma intensity of commercial aged full-fat Cheddar Cheeses. PRACTICAL APPLICATION The market for reduced-fat Cheddar Cheese is increasing as consumers become more health conscious. The structure and biochemistry of reduced-fat Cheddar Cheeses are altered, and Flavor and texture remain a challenge. This study established the role of 23 volatile compounds using descriptive analysis of Cheese model systems. The impact of key compound concentration differences and how these differences affect sensory perception of Cheese Flavor in full- and 75% reduced-fat Cheddar Cheeses were determined. These results provide guidance for mimicking aged Cheddar Cheese Flavor in reduced-fat Cheese.
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Consumer preferences for mild cheddar Cheese Flavors.
Journal of food science, 2008Co-Authors: S L Drake, P D Gerard, Mary Anne DrakeAbstract:Flavor is an important factor in consumer selection of Cheeses. Mild Cheddar Cheese is the classification used to describe Cheddar Cheese that is not aged extensively and has a "mild" Flavor. However, there is no legal definition or age limit for Cheddar Cheese to be labeled mild, medium, or sharp, nor are the Flavor profiles or Flavor expectations of these Cheeses specifically defined. The objectives of this study were to document the distinct Flavor profiles among commercially labeled mild Cheddar Cheeses, and to characterize if consumer preferences existed for specific mild Cheddar Cheese Flavors or Flavor profiles. Flavor descriptive sensory profiles of a representative array of commercial Cheddar Cheeses labeled as mild (n= 22) were determined using a trained sensory panel and an established Cheese Flavor sensory language. Nine representative Cheddar Cheeses were selected for consumer testing. Consumers (n= 215) assessed the Cheeses for overall liking and other consumer liking attributes. Internal preference mapping, cluster analysis, and discriminant analysis were conducted. Mild Cheddar Cheeses were diverse in Flavor with many displaying Flavors typically associated with more age. Four distinct consumer clusters were identified. The key drivers of liking for mild Cheddar Cheese were: color, cooked/milky, whey and brothy Flavors, and sour taste. Consumers have distinct Flavor and color preferences for mild Cheddar Cheese. These results can help manufacturers understand consumer preferences for mild Cheddar Cheese.
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Microbiological, Chemical, and Sensory Characteristics of Swiss Cheese Manufactured with Adjunct Lactobacillus Strains Using a Low Cooking Temperature
Journal of Dairy Science, 2008Co-Authors: N.a. Kocaoglu-vurma, Mary Anne Drake, W.j. Harper, P.d. CourtneyAbstract:The effect of nonstarter Lactobacillus adjunct cultures on the microbial, chemical, and sensory characteristics of Swiss Cheese manufactured using the "kosher make procedure" was investigated. The kosher make procedure, which uses a lower cooking temperature than traditional Swiss Cheese making, is used by many American Cheese manufacturers to allow for kosher-certified whey. Cheeses were manufactured using a commercial starter culture combination and 1 of 3 non-starter Lactobacillus strains previously isolated from Swiss Cheeses, Lactobacillus casei A26, L. casei B21, and Lactobacillus rhamnosus H2, as an adjunct. Control Cheeses lacked the adjunct culture. Cheeses were analyzed during ripening for microbial and chemical composition. Adjunct strain L. casei A26, which utilized citrate most readily in laboratory medium, dominated the Lactobacillus population within 30 d, faster than the other adjunct cultures. There were no significant differences in Propionibacterium counts, Streptococcus thermophilus counts, protein, fat, moisture, salt, and pH among the Cheeses. Free amino acid concentration ranged from 5 to 7 mmol/100 g of Cheese at 90 d of ripening and was adjunct strain dependent. Lactic, acetic, and propionic acid concentrations were not significantly different among the Cheeses after a 90-d ripening period; however differences in propionic acid concentrations were apparent at 60 d, with the Cheeses made with L. casei adjuncts containing less propionic acid. Citric acid was depleted by the end of warm room ripening in Cheeses manufactured with adjunct L. casei strains, but not with adjunct L. rhamnosus. Cheeses made with L. casei A26 were most similar to the control Cheeses in diacetyl and butyric/isobutyric acid abundance as evaluated by electronic nose during the first 3 mo of ripening. The 4 Cheese types differed in their descriptive sensory profiles at 8 mo of age, indicating an adjunct strain-dependent effect on particular Flavor attributes. Adjunct Lactobacillus spp. affected the Flavor profile and concentration of some Flavor compounds in Swiss Cheeses produced with the kosher make procedure. Use of adjunct Lactobacillus cultures provides Swiss Cheese makers using a low cooking temperature with a means to control the dominant Lactobacillus strain during ripening, reduce citrate concentration, and modify Cheese Flavor.
Luis E Rodriguezsaona - One of the best experts on this subject based on the ideXlab platform.
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application of infrared microspectroscopy and multivariate analysis for monitoring the effect of adjunct cultures during swiss Cheese ripening
Journal of Dairy Science, 2009Co-Authors: G Chen, W.j. Harper, Nurdan A Kocaogluvurma, Luis E RodriguezsaonaAbstract:Abstract Improved Cheese Flavor has been attributed to the addition of adjunct cultures, which provide certain key enzymes for proteolysis and affect the dynamics of starter and nonstarter cultures. Infrared microspectroscopy provides unique fingerprint-like spectra for Cheese samples and allows for rapid monitoring of Cheese composition during ripening. The objective was to use infrared microspectroscopy and multivariate analysis to evaluate the effect of adjunct cultures on Swiss Cheeses during ripening. Swiss Cheeses, manufactured using a commercial starter culture combination and 1 of 3 adjunct Lactobacillus spp., were evaluated at d 1, 6, 30, 60, and 90 of ripening. Cheese samples (approximately 20 g) were powdered with liquid nitrogen and homogenized using water and organic solvents, and the water-soluble components were separated. A 3-μL aliquot of the extract was applied onto a reflective microscope slide, vacuum-dried, and analyzed by infrared microspectroscopy. The infrared spectra (900 to 1,800 cm −1 ) produced specific absorption profiles that allowed for discrimination among different Cheese samples. Cheeses manufactured with adjunct cultures showed more uniform and consistent spectral profiles, leading to the formation of tight clusters by pattern-recognition analysis (soft independent modeling of class analogy) as compared with Cheeses with no adjuncts, which exhibited more spectral variability among replicated samples. In addition, the soft independent modeling of class analogy discriminating power indicated that Cheeses were differentiated predominantly based on the band at 1,122 cm −1 , which was associated with S–O vibrations. The greatest changes in the chemical profile of each Cheese occurred between d 6 and 30 of warm-room ripening. The band at 1,412 cm −1 , which was associated with acidic AA, had the greatest contribution to differentiation, indicating substantial changes in levels of proteolysis during warm-room ripening in addition to propionic acid, acetic acid, and eye formation. A high-throughput infrared microspectroscopy technique was developed that can further the understanding of biochemical changes occurring during the ripening process and provide insight into the role of adjunct nonstarter lactic acid bacteria on the complex process of Flavor development in Cheeses.
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cheddar Cheese classification based on Flavor quality using a novel extraction method and fourier transform infrared spectroscopy
Journal of Dairy Science, 2009Co-Authors: A Subramanian, W.j. Harper, Luis E RodriguezsaonaAbstract:Abstract Analysis of Cheddar Cheese Flavor using trained sensory and grading panels is expensive and time consuming. A rapid and simple solvent extraction procedure in combination with Fourier transform infrared spectroscopy was developed for classifying Cheddar Cheese based on Flavor quality. Fifteen Cheddar Cheese samples from 2 commercial production plants were ground into powders using liquid nitrogen. The water-soluble compounds from the Cheese powder, without interfering compounds such as fat and protein, were extracted using water, chloroform, and ethanol. Aliquots (10μL) of the extract were placed on a zinc selenide crystal, vacuum dried, and scanned in the mid-infrared region (4,000 to 700cm −1 ). The infrared spectra were analyzed by soft independent modeling of class analogy (SIMCA) for pattern recognition. Sensory Flavor quality of these Cheeses was determined by trained quality assurance personnel in the production facilities. The SIMCA models provided 3-dimensional classification plots in which all the 15 Cheese samples formed well-separated clusters. The orientation of the clusters in 3-dimensional space correlated well with their Cheese Flavor characteristics (fermented, unclean, low Flavor, sour, good Cheddar, and so on). The discrimination of the samples in the SIMCA plot was mainly due to organic acids, fatty acids and their esters, and amino acids (1,450 to 1,350 and 1,200 to 990cm −1 ), which are known to contribute significantly to Cheese Flavor. The total analysis time, including the sample preparation time, was less than 20min per sample. This technique can be a rapid, inexpensive, and simple tool to the Cheese industry for predicting the Flavor quality of Cheese.
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application of fourier transform infrared spectroscopy for monitoring short chain free fatty acids in swiss Cheese
Journal of Dairy Science, 2007Co-Authors: W.j. Harper, Luis E Rodriguezsaona, Nurcan Koca, V B AlvarezAbstract:Short-chain free fatty acids (FFA) are important sources of Cheese Flavor and have been reported to be indicators for assessing quality. The objective of this research was to develop a simple and rapid screening tool for monitoring the short-chain FFA contents in Swiss Cheese by using Fourier transform infrared spectroscopy (FTIR). Forty-four Swiss Cheese samples were evaluated by using a MIRacle three-reflection diamond attenuated total reflectance (ATR) accessory. Two different sampling techniques were used for FTIR/ATR measurement: direct measurement of Swiss Cheese slices (approximately 0.5 g) and measurement of a water-soluble fraction of Cheese. The amounts of FFA (propionic, acetic, and butyric acids) in the water-soluble fraction of samples were analyzed by gas chromatography-flame ion-ization detection as a reference method. Calibration models for both direct measurement and the water-soluble fraction of Cheese were developed based on a cross-validated (leave-one-out approach) partial least squares regression by using the regions of 3,000 to 2,800, 1,775 to 1,680, and 1,500 to 900 cm(-1) for short-chain FFA in Cheese. Promising performance statistics were obtained for the calibration models of both direct measurement and the water-soluble fraction, with improved performance statistics obtained from the water-soluble extract, particularly for propionic acid. Partial least squares models generated from FTIR/ATR spectra by direct measurement of Cheeses gave standard errors of cross-validation of 9.7 mg/100 g of Cheese for propionic acid, 9.3 mg/100 g of Cheese for acetic acid, and 5.5 mg/100 g of Cheese for butyric acid, and correlation coefficients >0.9. Standard error of cross-validation values for the water-soluble fraction were 4.4 mg/100 g of Cheese for propionic acid, 9.2 mg/100 g of Cheese for acetic acid, and 5.2 mg/100 g of Cheese for butyric acid with correlation coefficients of 0.98, 0.95, and 0.92, respectively. Infrared spectroscopy and chemometrics accurately and precisely predicted the short-chain FFA content in Swiss Cheeses and in the water-soluble fraction of the Cheese.
W.j. Harper - One of the best experts on this subject based on the ideXlab platform.
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application of infrared microspectroscopy and multivariate analysis for monitoring the effect of adjunct cultures during swiss Cheese ripening
Journal of Dairy Science, 2009Co-Authors: G Chen, W.j. Harper, Nurdan A Kocaogluvurma, Luis E RodriguezsaonaAbstract:Abstract Improved Cheese Flavor has been attributed to the addition of adjunct cultures, which provide certain key enzymes for proteolysis and affect the dynamics of starter and nonstarter cultures. Infrared microspectroscopy provides unique fingerprint-like spectra for Cheese samples and allows for rapid monitoring of Cheese composition during ripening. The objective was to use infrared microspectroscopy and multivariate analysis to evaluate the effect of adjunct cultures on Swiss Cheeses during ripening. Swiss Cheeses, manufactured using a commercial starter culture combination and 1 of 3 adjunct Lactobacillus spp., were evaluated at d 1, 6, 30, 60, and 90 of ripening. Cheese samples (approximately 20 g) were powdered with liquid nitrogen and homogenized using water and organic solvents, and the water-soluble components were separated. A 3-μL aliquot of the extract was applied onto a reflective microscope slide, vacuum-dried, and analyzed by infrared microspectroscopy. The infrared spectra (900 to 1,800 cm −1 ) produced specific absorption profiles that allowed for discrimination among different Cheese samples. Cheeses manufactured with adjunct cultures showed more uniform and consistent spectral profiles, leading to the formation of tight clusters by pattern-recognition analysis (soft independent modeling of class analogy) as compared with Cheeses with no adjuncts, which exhibited more spectral variability among replicated samples. In addition, the soft independent modeling of class analogy discriminating power indicated that Cheeses were differentiated predominantly based on the band at 1,122 cm −1 , which was associated with S–O vibrations. The greatest changes in the chemical profile of each Cheese occurred between d 6 and 30 of warm-room ripening. The band at 1,412 cm −1 , which was associated with acidic AA, had the greatest contribution to differentiation, indicating substantial changes in levels of proteolysis during warm-room ripening in addition to propionic acid, acetic acid, and eye formation. A high-throughput infrared microspectroscopy technique was developed that can further the understanding of biochemical changes occurring during the ripening process and provide insight into the role of adjunct nonstarter lactic acid bacteria on the complex process of Flavor development in Cheeses.
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Rapid prediction of composition and Flavor quality of cheddar Cheese using ATR-FTIR spectroscopy
Journal of Food Science, 2009Co-Authors: A Subramanian, W.j. Harper, Luis E. Rodriguez-saonaAbstract:ABSTRACT: Multiple methods are required for analysis of Cheese Flavor quality and composition. Chromatography and sensory analyses are accurate but laborious, expensive, and time consuming. A rapid and simple instrumental method based on Fourier transform infrared (FTIR) spectroscopy was developed for simultaneous analysis of Cheddar Cheese composition and Flavor quality. Twelve different Cheddar Cheese samples ripened for 67 d were obtained from a commercial Cheese manufacturer along with their moisture, pH, salt, fat content, and sensory Flavor quality data. Water-soluble components were extracted from the Cheese, dried on zinc selenide FTIR crystal and scanned (4000 to 700 cm−1). Infrared spectra of the samples were correlated with their composition and Flavor quality data to develop multivariate statistical regression and classification models. The models were validated using an independent set of ten 67-d-old test samples. The infrared spectra of the samples were well defined, highly consistent within each sample and distinct from other samples. The regression models showed excellent fit (r > 0.92) and could accurately determine moisture, pH, salt, and fat contents as well as the Flavor quality rating in less than 20 min. Furthermore, Cheeses could also be classified based on their Flavor quality (slight acid, whey taint, good cheddar, and so on). The discrimination of the samples was due to organic acids, amino acids, and short chain fatty acids (1800 to 900 cm−1), which are known to contribute significantly to Cheese Flavor. The results show that this technique can be a rapid, inexpensive, and simple tool for predicting composition and Flavor quality of Cheese.
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cheddar Cheese classification based on Flavor quality using a novel extraction method and fourier transform infrared spectroscopy
Journal of Dairy Science, 2009Co-Authors: A Subramanian, W.j. Harper, Luis E RodriguezsaonaAbstract:Abstract Analysis of Cheddar Cheese Flavor using trained sensory and grading panels is expensive and time consuming. A rapid and simple solvent extraction procedure in combination with Fourier transform infrared spectroscopy was developed for classifying Cheddar Cheese based on Flavor quality. Fifteen Cheddar Cheese samples from 2 commercial production plants were ground into powders using liquid nitrogen. The water-soluble compounds from the Cheese powder, without interfering compounds such as fat and protein, were extracted using water, chloroform, and ethanol. Aliquots (10μL) of the extract were placed on a zinc selenide crystal, vacuum dried, and scanned in the mid-infrared region (4,000 to 700cm −1 ). The infrared spectra were analyzed by soft independent modeling of class analogy (SIMCA) for pattern recognition. Sensory Flavor quality of these Cheeses was determined by trained quality assurance personnel in the production facilities. The SIMCA models provided 3-dimensional classification plots in which all the 15 Cheese samples formed well-separated clusters. The orientation of the clusters in 3-dimensional space correlated well with their Cheese Flavor characteristics (fermented, unclean, low Flavor, sour, good Cheddar, and so on). The discrimination of the samples in the SIMCA plot was mainly due to organic acids, fatty acids and their esters, and amino acids (1,450 to 1,350 and 1,200 to 990cm −1 ), which are known to contribute significantly to Cheese Flavor. The total analysis time, including the sample preparation time, was less than 20min per sample. This technique can be a rapid, inexpensive, and simple tool to the Cheese industry for predicting the Flavor quality of Cheese.
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Microbiological, Chemical, and Sensory Characteristics of Swiss Cheese Manufactured with Adjunct Lactobacillus Strains Using a Low Cooking Temperature
Journal of Dairy Science, 2008Co-Authors: N.a. Kocaoglu-vurma, Mary Anne Drake, W.j. Harper, P.d. CourtneyAbstract:The effect of nonstarter Lactobacillus adjunct cultures on the microbial, chemical, and sensory characteristics of Swiss Cheese manufactured using the "kosher make procedure" was investigated. The kosher make procedure, which uses a lower cooking temperature than traditional Swiss Cheese making, is used by many American Cheese manufacturers to allow for kosher-certified whey. Cheeses were manufactured using a commercial starter culture combination and 1 of 3 non-starter Lactobacillus strains previously isolated from Swiss Cheeses, Lactobacillus casei A26, L. casei B21, and Lactobacillus rhamnosus H2, as an adjunct. Control Cheeses lacked the adjunct culture. Cheeses were analyzed during ripening for microbial and chemical composition. Adjunct strain L. casei A26, which utilized citrate most readily in laboratory medium, dominated the Lactobacillus population within 30 d, faster than the other adjunct cultures. There were no significant differences in Propionibacterium counts, Streptococcus thermophilus counts, protein, fat, moisture, salt, and pH among the Cheeses. Free amino acid concentration ranged from 5 to 7 mmol/100 g of Cheese at 90 d of ripening and was adjunct strain dependent. Lactic, acetic, and propionic acid concentrations were not significantly different among the Cheeses after a 90-d ripening period; however differences in propionic acid concentrations were apparent at 60 d, with the Cheeses made with L. casei adjuncts containing less propionic acid. Citric acid was depleted by the end of warm room ripening in Cheeses manufactured with adjunct L. casei strains, but not with adjunct L. rhamnosus. Cheeses made with L. casei A26 were most similar to the control Cheeses in diacetyl and butyric/isobutyric acid abundance as evaluated by electronic nose during the first 3 mo of ripening. The 4 Cheese types differed in their descriptive sensory profiles at 8 mo of age, indicating an adjunct strain-dependent effect on particular Flavor attributes. Adjunct Lactobacillus spp. affected the Flavor profile and concentration of some Flavor compounds in Swiss Cheeses produced with the kosher make procedure. Use of adjunct Lactobacillus cultures provides Swiss Cheese makers using a low cooking temperature with a means to control the dominant Lactobacillus strain during ripening, reduce citrate concentration, and modify Cheese Flavor.
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application of fourier transform infrared spectroscopy for monitoring short chain free fatty acids in swiss Cheese
Journal of Dairy Science, 2007Co-Authors: W.j. Harper, Luis E Rodriguezsaona, Nurcan Koca, V B AlvarezAbstract:Short-chain free fatty acids (FFA) are important sources of Cheese Flavor and have been reported to be indicators for assessing quality. The objective of this research was to develop a simple and rapid screening tool for monitoring the short-chain FFA contents in Swiss Cheese by using Fourier transform infrared spectroscopy (FTIR). Forty-four Swiss Cheese samples were evaluated by using a MIRacle three-reflection diamond attenuated total reflectance (ATR) accessory. Two different sampling techniques were used for FTIR/ATR measurement: direct measurement of Swiss Cheese slices (approximately 0.5 g) and measurement of a water-soluble fraction of Cheese. The amounts of FFA (propionic, acetic, and butyric acids) in the water-soluble fraction of samples were analyzed by gas chromatography-flame ion-ization detection as a reference method. Calibration models for both direct measurement and the water-soluble fraction of Cheese were developed based on a cross-validated (leave-one-out approach) partial least squares regression by using the regions of 3,000 to 2,800, 1,775 to 1,680, and 1,500 to 900 cm(-1) for short-chain FFA in Cheese. Promising performance statistics were obtained for the calibration models of both direct measurement and the water-soluble fraction, with improved performance statistics obtained from the water-soluble extract, particularly for propionic acid. Partial least squares models generated from FTIR/ATR spectra by direct measurement of Cheeses gave standard errors of cross-validation of 9.7 mg/100 g of Cheese for propionic acid, 9.3 mg/100 g of Cheese for acetic acid, and 5.5 mg/100 g of Cheese for butyric acid, and correlation coefficients >0.9. Standard error of cross-validation values for the water-soluble fraction were 4.4 mg/100 g of Cheese for propionic acid, 9.2 mg/100 g of Cheese for acetic acid, and 5.2 mg/100 g of Cheese for butyric acid with correlation coefficients of 0.98, 0.95, and 0.92, respectively. Infrared spectroscopy and chemometrics accurately and precisely predicted the short-chain FFA content in Swiss Cheeses and in the water-soluble fraction of the Cheese.
Mireille Yvon - One of the best experts on this subject based on the ideXlab platform.
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The d-2-Hydroxyacid Dehydrogenase Incorrectly Annotated PanE Is the Sole Reduction System for Branched-Chain 2-Keto Acids in Lactococcus lactis
Journal of Bacteriology, 2008Co-Authors: Emilie Chambellon, Liesbeth Rijnen, Frédérique Lorquet, Christophe Gitton, Johan E. T. Van Hylckama Vlieg, Jeroen Wouters, Mireille YvonAbstract:Hydroxyacid dehydrogenases of lactic acid bacteria, which catalyze the stereospecific reduction of branched-chain 2-keto acids to 2-hydroxyacids, are of interest in a variety of fields, including Cheese Flavor formation via amino acid catabolism. In this study, we used both targeted and random mutagenesis to identify the genes responsible for the reduction of 2-keto acids derived from amino acids in Lactococcus lactis. The gene panE, whose inactivation suppressed hydroxyisocaproate dehydrogenase activity, was cloned and overexpressed in Escherichia coli, and the recombinant His-tagged fusion protein was purified and characterized. The gene annotated panE was the sole gene responsible for the reduction of the 2-keto acids derived from leucine, isoleucine, and valine, while ldh, encoding l-lactate dehydrogenase, was responsible for the reduction of the 2-keto acids derived from phenylalanine and methionine. The kinetic parameters of the His-tagged PanE showed the highest catalytic efficiencies with 2-ketoisocaproate, 2-ketomethylvalerate, 2-ketoisovalerate, and benzoylformate (Vmax/Km ratios of 6,640, 4,180, 3,300, and 2,050 U/mg/mM, respectively), with NADH as the exclusive coenzyme. For the reverse reaction, the enzyme accepted d-2-hydroxyacids but not l-2-hydroxyacids. Although PanE showed the highest degrees of identity to putative NADP-dependent 2-ketopantoate reductases (KPRs), it did not exhibit KPR activity. Sequence homology analysis revealed that, together with the d-mandelate dehydrogenase of Enterococcus faecium and probably other putative KPRs, PanE belongs to a new family of d-2-hydroxyacid dehydrogenases which is unrelated to the well-described d-2-hydroxyisocaproate dehydrogenase family. Its probable physiological role is to regenerate the NAD+ necessary to catabolize branched-chain amino acids, leading to the production of ATP and aroma compounds.
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ability of thermophilic lactic acid bacteria to produce aroma compounds from amino acids
Applied and Environmental Microbiology, 2004Co-Authors: Sandra Helinck, Dominique Le Bars, Daniel Moreau, Mireille YvonAbstract:Amino acid catabolism by the microflora is a major process for the formation of a large number of key aroma compounds in Swiss-type Cheeses such as gruyere and emmental (7, 14, 17). However, the amino acid catabolic pathways in the different bacteria present in these Cheeses are not well known. This knowledge could lead to the development of cultures with optimized aromatic properties. Amino acid catabolism by Lactococcus lactis and mesophilic lactobacilli has been extensively studied recently (2, 8, 11, 19, 26; S. Gummalla and J. R. Broadbent, Abstract, J. Dairy Sci. 79(Suppl. 1):101, 1996). In these lactic acid bacteria (LAB), amino acid catabolism is mainly initiated by a transamination reaction, which requires the presence of an α-keto acid as the amino group acceptor. The production of an α-keto acid acceptor by LAB often limits amino acid catabolism, but strains exhibiting glutamate dehydrogenase (GDH) activity are capable of producing α-ketoglutarate (α-KG) from glutamate (Glu) and therefore are capable of degrading amino acids in a reaction medium containing Glu (20). The key aroma compounds identified in Swiss-type Cheese result mainly from the catabolism of branched-chain amino acids (3-methylbutanal, isobutyric acid, isovaleric acid, and their derived esters), methionine (methional, methanethiol, and dimethyl trisulfide), and phenylalanine (phenylacetic acid and phenylacetaldehyde). Most of these compounds are considered beneficial to the Cheese Flavor. Isobutyric acid and isovaleric acid participate in the sweaty and strong Cheese notes, respectively, while 3-methylbutanal has a malty aroma. All the compounds derived from methionine have sulfur notes that are appreciated in Cheese. Finally, phenylacetic acid and phenylacetaldehyde have a floral or fruity note. However, a few of them, such as methional and compounds derived from tryptophan such as indole, have been identified as being responsible for off Flavors when they are present in too high amounts (13, 17). The microflora of Swiss-type Cheese consists mainly of propionibacteria and thermophilic LAB, especially Lactobacillus helveticus, Lactobacillus delbrueckii subsp. lactis, and Streptococcus thermophilus. Recently, Thierry et al. have shown that propionibacteria are capable of producing isovaleric acid from leucine in vitro (21) and are mainly responsible for its production in Swiss Cheese (22). However, propionibacteria do not seem to be capable of producing aldehydes from amino acids, while these compounds are very important for Swiss Cheese aroma. Among the thermophilic LAB, only amino acid conversion by L. helveticus was partially studied. In vitro studies have shown that L. helveticus can produce acetaldehyde from threonine (10), volatile sulfur compounds from methionine (5, 18), and, in the presence of α-KG, benzaldehyde from phenylalanine (12). Under simulated Cheese-ripening conditions, L. helveticus cells mainly produces carboxylic acids and hydroxyacids from phenylalanine and tyrosine (9). Investigations of amino acid catabolism by S. thermophilus and L. delbrueckii subsp. lactis have been limited. Cystathionine-β-lyase activity, which is involved in the production of volatile sulfur compounds from methionine in Lactococcus lactis (6), has been detected in only one strain of L. delbrueckii subsp. lactis of five strains tested (3). The aim of the present study was to compare the in vitro abilities of L. delbrueckii subsp. lactis, L. helveticus, and S. thermophilus to produce aroma compounds from three amino acids, leucine, methionine, and phenylalanine, and to elucidate the catabolic pathways used by these bacteria. Here we report the results obtained with one laboratory strain of each species, but otherwise we used two other industrial strains for each species to determine if the amino acid catabolism was strain dependent.
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cooperation between lactococcus lactis and nonstarter lactobacilli in the formation of Cheese aroma from amino acids
Applied and Environmental Microbiology, 2003Co-Authors: Agnieszka Kieronczyk, Siv Skeie, Thor Langsrud, Mireille YvonAbstract:In Gouda and Cheddar type Cheeses the amino acid conversion to aroma compounds, which is a major process for aroma formation, is essentially due to lactic acid bacteria (LAB). In order to evaluate the respective role of starter and nonstarter LAB and their interactions in Cheese Flavor formation, we compared the catabolism of phenylalanine, leucine, and methionine by single strains and strain mixtures of Lactococcus lactis subsp. cremoris NCDO763 and three mesophilic lactobacilli. Amino acid catabolism was studied in vitro at pH 5.5, by using radiolabeled amino acids as tracers. In the presence of α-ketoglutarate, which is essential for amino acid transamination, the lactobacillus strains degraded less amino acids than L. lactis subsp. cremoris NCDO763, and produced mainly nonaromatic metabolites. L. lactis subsp. cremoris NCDO763 produced mainly the carboxylic acids, which are important compounds for Cheese aroma. However, in the reaction mixture containing glutamate, only two lactobacillus strains degraded amino acids significantly. This was due to their glutamate dehydrogenase (GDH) activity, which produced α-ketoglutarate from glutamate. The combination of each of the GDH-positive lactobacilli with L. lactis subsp. cremoris NCDO763 had a beneficial effect on the aroma formation. Lactobacilli initiated the conversion of amino acids by transforming them mainly to keto and hydroxy acids, which subsequently were converted to carboxylic acids by the Lactococcus strain. Therefore, we think that such cooperation between starter L. lactis and GDH-positive lactobacilli can stimulate Flavor development in Cheese.
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characterization and role of the branched chain aminotransferase bcat isolated from lactococcus lactis subsp cremoris ncdo 763
Applied and Environmental Microbiology, 2000Co-Authors: Mireille Yvon, Emilie Chambellon, Alexander Bolotin, Florence RoudotalgaronAbstract:In Lactococcus lactis, which is widely used as a starter in the Cheese industry, the first step of aromatic and branched-chain amino acid degradation is a transamination which is catalyzed by two major aminotransferases. We have previously purified and characterized biochemically and genetically the aromatic aminotransferase, AraT. In the present study, we purified and studied the second enzyme, the branched-chain aminotransferase, BcaT. We cloned and sequenced the corresponding gene and used a mutant, along with the luciferase gene as the reporter, to study the role of the enzyme in amino acid metabolism and to reveal the regulation of gene transcription. BcaT catalyzes transamination of the three branched-chain amino acids and methionine and belongs to class IV of the pyridoxal 5′-phosphate-dependent aminotransferases. In contrast to most of the previously described bacterial BcaTs, which are hexameric, this enzyme is homodimeric. It is responsible for 90% of the total isoleucine and valine aminotransferase activity of the cell and for 50 and 40% of the activity towards leucine and methionine, respectively. The original role of BcaT was probably biosynthetic since expression of its gene was repressed by free amino acids and especially by isoleucine. However, in dairy strains, which are auxotrophic for branched-chain amino acids, BcaT functions only as a catabolic enzyme that initiates the conversion of major aroma precursors. Since this enzyme is still active under Cheese-ripening conditions, it certainly plays a major role in Cheese Flavor development.
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an aminotransferase from lactococcus lactis initiates conversion of amino acids to Cheese Flavor compounds
Applied and Environmental Microbiology, 1997Co-Authors: Mireille Yvon, Liesbeth Rijnen, S Thirouin, D Fromentier, J C GriponAbstract:The enzymatic degradation of amino acids in Cheese is believed to generate aroma compounds and therefore to be involved in the complex process of Cheese Flavor development. In lactococci, transamination is the first step in the degradation of aromatic and branched-chain amino acids which are precursors of aroma compounds. Here, the major aromatic amino acid aminotransferase of a Lactococcus lactis subsp. cremoris strain was purified and characterized. The enzyme transaminates the aromatic amino acids, leucine, and methionine. It uses the ketoacids corresponding to these amino acids and alpha-ketoglutarate as amino group acceptors. In contrast to most bacterial aromatic aminotransferases, it does not act on aspartate and does not use oxaloacetate as second substrate. It is essential for the transformation of aromatic amino acids to Flavor compounds. It is a pyridoxal 5'-phosphate-dependent enzyme and is composed of two identical subunits of 43.5 kDa. The activity of the enzyme is optimal between pH 6.5 and 8 and between 35 and 45 degrees C, but it is still active under Cheese-ripening conditions.