Natural Cheeses Research Articles

Evaluation of X-ray fluorescence spectroscopy as a method for the rapid and direct determination of sodium in cheese

Cheese manufacturers indirectly determine Na in cheese by analysis of Cl using the Volhard method, assuming that all Cl came from NaCl. This method overestimates the actual Na content in cheeses when Na replacers (e.g., KCl) are used. A direct and rapid method for Na detection is needed. X-ray fluorescence spectroscopy (XRF), a mineral analysis technique used in the mining industry, was investigated as an alternative method of Na detection in cheese. An XRF method for the detection of Na in cheese was developed and compared with inductively coupled plasma optical emission spectroscopy (ICP-OES; the reference method for Na in cheese) and Cl analyzer. Sodium quantification was performed by multi-point calibration with cheese standards spiked with NaCl ranging from 0 to 4% Na (wt/wt). The Na concentration of each of the cheese standards (discs: 30mm×7mm) was quantified by the 3 methods. A single laboratory method validation was performed; linearity, precision, limit of detection, and limit of quantification were determined. An additional calibration graph was created using cheese standards made from natural or process cheeses manufactured with different ratios of Na:K. Both Na and K calibration curves were linear for the cheese standards. Sodium was quantified in a variety of commercial cheese samples. The Na data obtained by XRF were in agreement with those from ICP-OES and Cl analyzer for most commercial natural cheeses. The XRF method did not accurately determine Na concentration for several process cheese samples, compared with ICP-OES, likely due to the use of unknown types of Na-based emulsifying salts (ES). When a calibration curve was created for process cheese with the specific types of ES used for this cheese, Na content was successfully predicted in the samples. For natural cheeses, the limit of detection and limit of quantification for Na that can be determined with an acceptable level of repeatability, precision, and trueness was 82 and 246mg/100g of cheese, respectively. Calibration graphs should be created with standards that reflect the concentration range, ratio, and salt type present in the cheeses. This XRF method can be successfully used for the rapid and direct measurement of Na content in a wide variety of natural cheeses. Commercial process cheese manufacturers use proprietary blends of ES. We did find that the XRF technique worked for process cheese when the calibration graphs were created with the specific types of ES actually used.

Improved Pretreatment Method for Determination of Nisins A and Z and Monitoring in Cheese Using Liquid Chromatrography-Tandem Mass Spectrometry

The peptide nisin produced by Lactococcus lactis subsp. lactis is known to be one of the natural preservatives that are used in various foods including cheese products. This study optimized and validated a liquid chromatography-tandem mass spectrometry method for determining nisin A and nisin Z in cheese. Processed and natural cheeses were used for method validation. In addition, this study investigated the content of nisin A and nisin Z in 140 cheese samples comprised of imported and domestic cheese. The nisin A and nisin Z contents of 140 cheese samples were determined. An extraction solution consisting of 0.1 M acetate buffer containing 1 M NaCl (pH 2.0) and methanol (NaCl/MeOH, 1:1 v/v) was the optimal solution for nisin extraction from cheese. The limits of quantification of nisin A and nisin Z were approximately 10.2 and 12.6 μg/kg, respectively. For processed cheese and natural cheese, the recoveries were 80.1–107.3 % for nisin A and 74.4–113.9 % for nisin Z and low coefficients of variation. In monitoring study, nisins A and Z were detected in only three soft processed cheese out of 140 samples. The proposed analysis procedure can be used as an efficient tool for determination of nisin A and nisin Z in cheese using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Understanding the role of natural cheese calcium and phosphorous content, residual lactose and salt‐in‐moisture content on block‐type processed cheese functional properties: Cheese hardness and flowability/meltability

Four treatments of natural Cheddar cheese with two levels (high and low) of calcium (Ca) and phosphorus (P), and two levels (high and low) of residual lactose were manufactured. Each treatment was subsequently split prior to the salting step of cheese manufacturing processed and salted at two levels (high and low) for a total of eight treatments. The eight treatments included: high Ca and P, high lactose, high salt‐in‐moisture (S/M) content (HHH); high Ca and P, high lactose, low S/M (HHL); high Ca and P, low lactose, high S/M (HLH); high Ca and P, low lactose, low S/M (HLL); low Ca and P, high lactose, high S/M (LHH); low Ca and P, high lactose, low S/M (LHL); low Ca and P, low lactose, high S/M (LLH); and low Ca and P, low lactose, low S/M (LLL). After 2 months of ripening, each treatment of natural Cheddar cheese was used to manufacture processed cheese using a twin‐screw Blentech processed cheese cooker. All of the processed cheese food formulations were balanced for moisture, fat and salt. Texture and melt‐flow characteristics of the processed cheese were evaluated with different techniques, including texture profile analysis (TPA) for hardness and melt profile analysis. There was a considerable increase in cheese hardness for the processed cheeses prepared from high Ca and P content, and high S/M natural cheeses compared with low Ca and P content and low S/M natural cheeses. Moreover, definite decrease in flow rate and extent of flow was observed for processed cheeses manufactured from high Ca and P content, and high S/M natural cheeses than that of low Ca and P content and low S/M natural cheeses. No considerable trend was observed in hardness and melt‐flow characteristics for the processed cheeses manufactured from high and low residual lactose content natural Cheddar cheeses. This study strongly demonstrates that the characteristics of natural cheese (calcium and phosphorus content, lactose content and salt‐in‐moisture content) used in processed cheese manufacture have a significant impact on processed cheese functionality.

Current Trends in Nonfat Dairy Production

This article is dedicated to the development of new nonfat dairy products and methods of improving the quality of low-calorie foods. Advantages and drawbacks of the consumer properties of nonfat dairy products are shown. Some carbohydrate and protein fat imitators are characterized. The advantages of protein fat imitators are shown that are able not only to increase the protein content but also to add a creamy flavor to nonfat products. Possible options of using whey protein microparticulates as fat imitators in the production of nonfat dairy products are considered. The research findings are given on the use of whey protein microparticulates in the production of dairy products with higher protein contents: curd products, sweetened condensed milk, and natural cheeses: thermal- acid, soft acid-rennet, and brined.

Kinetic Behavior of Escherichia coli on Various Cheeses under Constant and Dynamic Temperature.

In this study, we developed kinetic models to predict the growth of pathogenic Escherichia coli on cheeses during storage at constant and changing temperatures. A five-strain mixture of pathogenic E. coli was inoculated onto natural cheeses (Brie and Camembert) and processed cheeses (sliced Mozzarella and sliced Cheddar) at 3 to 4 log CFU/g. The inoculated cheeses were stored at 4, 10, 15, 25, and 30°C for 1 to 320 h, with a different storage time being used for each temperature. Total bacteria and E. coli cells were enumerated on tryptic soy agar and MacConkey sorbitol agar, respectively. E. coli growth data were fitted to the Baranyi model to calculate the maximum specific growth rate (μmax; log CFU/g/h), lag phase duration (LPD; h), lower asymptote (log CFU/g), and upper asymptote (log CFU/g). The kinetic parameters were then analyzed as a function of storage temperature, using the square root model, polynomial equation, and linear equation. A dynamic model was also developed for varying temperature. The model performance was evaluated against observed data, and the root mean square error (RMSE) was calculated. At 4°C, E. coli cell growth was not observed on any cheese. However, E. coli growth was observed at 10°C to 30°C with a μmax of 0.01 to 1.03 log CFU/g/h, depending on the cheese. The μmax values increased as temperature increased, while LPD values decreased, and μmax and LPD values were different among the four types of cheese. The developed models showed adequate performance (RMSE = 0.176–0.337), indicating that these models should be useful for describing the growth kinetics of E. coli on various cheeses.

Growth kinetics of Staphylococcus aureus on Brie and Camembert cheeses.

In this study, we developed mathematical models to describe the growth kinetics of Staphylococcus aureus on natural cheeses. A five-strain mixture of Staph. aureus was inoculated onto 15g of Brie and Camembert cheeses at 4log CFU/g. The samples were then stored at 4, 10, 15, 25, and 30°C for 2-60d, with a different storage time being used for each temperature. Total bacterial and Staph. aureus cells were enumerated on tryptic soy agar and mannitol salt agar, respectively. The Baranyi model was fitted to the growth data of Staph. aureus to calculate kinetic parameters such as the maximum growth rate in log CFU units (r max; log CFU/g/h) and the lag phase duration (λ; h). The effects of temperature on the square root of r max and on the natural logarithm of λ were modelled in the second stage (secondary model). Independent experimental data (observed data) were compared with prediction and the respective root mean square error compared with the RMSE of the fit on the original data, as a measure of model performance. The total growth of bacteria was observed at 10, 15, 25, and 30°C on both cheeses. The r max values increased with storage temperature (P<0·05), but a significant effect of storage temperature on λ values was only observed between 4 and 15°C (P<0·05). The square root model and linear equation were found to be appropriate for description of the effect of storage temperature on growth kinetics (R 2=0·894-0·983). Our results indicate that the models developed in this study should be useful for describing the growth kinetics of Staph. aureus on Brie and Camembert cheeses.

Classification and Functional Properties of Processed Cheese

Processed cheese is manufactured by mixing natural cheeses with emulsifying salts and other ingredients and heating under agitation to produce a homogeneous product. Processed cheese, processed cheese food, and processed cheese spread are classified in the US standards for processed cheese. The functional properties of processed cheese, such as firmness and meltability, are regarded as a quality indicator assessing overall cheese quality and consumer preference. Various analytical methods have been developed to determine the functional properties of processed cheese. In this review, the classification and functional properties of processed cheeses are described and analytical tools for evaluating the functional properties of processed cheese are discussed.

Physical Properties of an Imitation Cheese as Affected by Emulsifying Salts and Citric Acid

Effects of emulsifying salts and citric acid on meltability and textural properties of a starch-based imitation cheese were investigated. Imitation cheeses were produced according to the same basic formula with varying concentrations of emulsifying salts and citric acid. While increasing the concentration of emulsifying salts increased hardness, citric acid at high concentration was found to prevent melting of the imitation cheese. Two of the imitation cheese samples with the highest and lowest concentrations of emulsifying salts and citric acid were stored at 4C for 3 months and changes in their meltability and textural properties were determined. Hardness of the sample prepared with the highest amounts of emulsifying salts and citric acid increased after 30 days of storage as a result of retrogradation of starch. Cohesiveness of both samples declined during storage. Practical Applications Imitation cheeses manufactured by using starch for replacement of protein are being investigated and produced for reducing cost of cheese manufacture and also for special consumer groups like phenylketonuria patients. This type of cheese is produced according to the method of manufacture of processed cheeses. However, obtaining a meltability value similar to those of processed or natural cheeses is a major challenge in its manufacture especially when the amount of starch is high. In addition, there is a lack of information in the literature for storage stability of this type of imitation cheese. This study addresses these two issues for improvement of this kind of imitation cheese.

Monitoring the ripening process of Cheddar cheese based on hydrophilic component profiling using gas chromatography-mass spectrometry

We proposed an application methodology that combines metabolic profiling with multiple appropriate multivariate analyses and verified it on the industrial scale of the ripening process of Cheddar cheese to make practical use of hydrophilic low-molecular-weight compound profiling using gas chromatography-mass spectrometry to design optimal conditions and quality monitoring of the cheese ripening process. Principal components analysis provided an overview of the effect of sodium chloride content and kind of lactic acid bacteria starter on the metabolic profile in the ripening process of Cheddar cheese and orthogonal partial least squares-discriminant analysis unveiled the difference in characteristic metabolites. When the sodium chloride contents were different (1.6 and 0.2%) but the same lactic acid bacteria starter was used, the 2 cheeses were classified by orthogonal partial least squares-discriminant analysis from their metabolic profiles, but were not given perfect discrimination. Not much difference existed in the metabolic profile between the 2 cheeses. Compounds including lactose, galactose, lactic acid, 4-aminobutyric acid, and phosphate were identified as contents that differed between the 2 cheeses. On the other hand, in the case of the same salt content of 1.6%, but different kinds of lactic acid bacteria starter, an excellent distinctive discrimination model was obtained, which showed that the difference of lactic acid bacteria starter caused an obvious difference in metabolic profiles. Compounds including lactic acid, lactose, urea, 4-aminobutyric acid, galactose, phosphate, proline, isoleucine, glycine, alanine, lysine, leucine, valine, and pyroglutamic acid were identified as contents that differed between the 2 cheeses. Then, a good sensory prediction model for “rich flavor,” which was defined as “thick and rich, including umami taste and soy sauce-like flavor,” was constructed based on the metabolic profile during ripening using partial least squares regression analysis. The amino acids proline, leucine, valine, isoleucine, pyroglutamic acid, alanine, glutamic acid, glycine, lysine, tyrosine, serine, phenylalanine, methionine, aspartic acid, and ornithine were extracted as ripening process markers. The present study is not limited to Cheddar cheese and can be applied to various maturation-type natural cheeses. This study provides the technical platform for designing optimal conditions and quality monitoring of the cheese ripening process.

Distribution of antimicrobial‐resistant lactic acid bacteria in natural cheese in Japan

To determine and compare the extent of contamination caused by antimicrobial-resistant lactic acid bacteria (LAB) in imported and domestic natural cheeses on the Japanese market, LAB were isolated using deMan, Rogosa and Sharpe (MRS) agar and MRS agar supplemented with six antimicrobials. From 38 imported and 24 Japanese cheeses, 409 LAB isolates were obtained and their antimicrobial resistance was tested. The percentage of LAB resistant to dihydrostreptomycin, erythromycin, and/or oxytetracycline isolated from imported cheeses (42.1%) was significantly higher than that of LAB resistant to dihydrostreptomycin or oxytetracycline from cheeses produced in Japan (16.7%; P=0.04). Antimicrobial resistance genes were detected in Enterococcus faecalis (tetL, tetM, and ermB; tetL and ermB; tetM) E. faecium (tetM), Lactococcus lactis (tetS), Lactobacillus (Lb.), casei/paracasei (tetM or tetW), and Lb. rhamnosus (ermB) isolated from seven imported cheeses. Moreover, these E. faecalis isolates were able to transfer antimicrobial resistance gene(s). Although antimicrobial resistance genes were not detected in any LAB isolates from Japanese cheeses, Lb. casei/paracasei and Lb. coryniformis isolates from a Japanese farm-made cheese were resistant to oxytetracycline (minimal inhibitory concentration [MIC], 32 µg/mL). Leuconostoc isolates from three Japanese farm-made cheeses were also resistant to dihydrostreptomycin (MIC, 32 to >512 µg/mL). In conclusion, the present study demonstrated contamination with antimicrobial-resistant LAB in imported and Japanese farm-made cheeses on the Japanese market, but not in Japanese commercial cheeses.

Preparation and Quality Evaluation of Processed Cheese Made from Different Cheeses and Paneer

Processed cheese (PC), a modified form of natural cheese was prepared mixing with different proportions of Cheese and Paneer; Yak cheese and Kanchan cheese (70:30), Yak and Kanchan (30:70), Kanchan and Mozzarella (75:25), Yak, Kanchan, Mozzarella and Paneer (30:45:15:10) and Kanchan and Paneer (85:15) with PC made in DDC, Nepal as a control. Five experimental products were subjected for sensory and physico-chemical analysis. The physico-chemical parameters of processed cheeses were significantly (p&lt;0.05) varied among each other products due to different combination of natural cheeses. The PC made from Yak and Kanchan cheese (30:70) was found to be superior (p&lt;0.05) in terms overall sensory attributes. From the results of physico-chemicals and sensory analysis it was concluded that PC made from Yak and Kanchan (30:70) was the best formulation among all. J. Food Sci. Technol. Nepal, Vol. 6 (84-87), 2010 DOI: http://dx.doi.org/10.3126/jfstn.v6i0.8266

Microbial Assessment and Prevalence of Foodborne Pathogens in Natural Cheeses in Japan

The production and consumption of domestic natural cheese in Japan is increasing year by year. More than ninety percent of domestic natural cheese is produced in Hokkaido region of Japan, while information on its quality and safety related to foodborne pathogens is limited. To assess the microbiological safety of domestic natural cheese, a total of 126 natural cheese samples produced in Hokkaido were collected from December, 2012, to July, 2013. In addition to standard plate count (SPC) and coliform counts, the prevalence study of three pathogens (Listeria monocytogenes, pathogenic Escherichia coli, and Salmonella spp.) was performed on each sample. Real-time PCR and matrix-assisted laser desorption-ionization time-of-flight mass spectrometer methods were employed for identification of presumptive pathogens. Coliform was detected in 25 samples (19.8%) with a minimum of 25 cfu/g and a maximum of more than 3.0 × 106 cfu/g. Salmonella spp. and L. monocytogenes were not isolated from any of the samples. Only one sample (0.80%) showed positive PCR amplification for ipaH gene suggesting possible contamination of enteroinvasive E. coli or Shigella in this product. Overall results indicate that natural cheeses produced in Hokkaido region were satisfactory microbiological quality according to existing international standards.

Metabolic fingerprinting of hard and semi-hard natural cheeses using gas chromatography with flame ionization detector for practical sensory prediction modeling

Metabolic fingerprinting using gas chromatography with flame ionization detector (GC/FID) was used to generate a practical metabolomics-based tool for quality evaluation of natural cheese. Hydrophilic low molecular weight components, relating to sensory characteristics, including amino acids, fatty acids, amines, organic acids, and saccharides, were extracted and derivatized prior to the analysis. Data on 12 cheeses, six Cheddar cheeses and six Gouda cheeses, were analyzed by multivariate analysis. Prediction models for two sensory attributes relating to maturation, "Rich flavor" and "Sour flavor", were constructed with 4199 data points from GC/FID, and excellent predictability was validated. Chromatograms from GC/FID and gas chromatography/time-of-flight-mass spectrometry (GC/TOF-MS) were comparable when the same column was used. Although GC/FID alone cannot identify peaks, the mutually complementary relationship between GC/FID and GC/MS does allow peak identification. Compounds contributing significantly to the sensory predictive models included lactose, succinic acid, L-lactic acid, and aspartic acid for "Rich flavor", and lactose, L-lactic acid, and succinic acid for "Sour flavor". Since similar model precision was obtained using GC/FID and GC/TOF-MS, metabolic fingerprinting using GC/FID, which is a relatively inexpensive instrument compared with GC/MS, is easy to maintain and operate, and is a valid alternative when metabolomics (especially using GC/MS) is to be used in a practical setting as a novel quality evaluation tool for manufacturing processes or final products.

The Toxic Aldehyde, 4‐Hydroxy‐2‐trans‐nonenal (HNE) Formation in Natural and Imitation Mozzarella Cheeses: Heat Treatment Effects

AbstractThe formation of 4‐hydroxy‐2‐trans‐nonenal (HNE), a toxic aldehyde formation, was investigated in heat treated imitation Mozzarella cheeses which are made with vegetable oils and in natural Mozzarella cheeses which contain dairy fats. The cheeses were heat treated at 204 °C for 30 and 60 min, and at 232 °C for 15 and 30 min. The HNE formations were much higher in imitation cheeses than in natural cheeses due to both heat treatments. Average HNE concentrations in imitation cheeses, after 30 min of heat treatment at 204 °C, were 110.3 ng HNE/g cheese and it increased to 877.1 ng HNE/g cheese when the temperature was raised to 232 °C. In natural cheeses, the average HNE concentration was much lower only 13.4 ng HNE/g cheese after 204 °C heat treatment for 30 min and it increased only to 182.8 ng HNE/g cheese using 232 °C. Since imitation cheeses are made with vegetable oils which contain much higher levels of linoleic acid, a precursor for HNE, than dairy fat, it is not surprising that heat‐induced lipid peroxidation results in increased HNE formation in imitations cheeses compared to dairy fat containing cheeses, which are low in linoleic acid.

Flavor Comparison of Natural Cheeses Manufactured in Different Countries

The objective of this study was to determine the main flavor components of different natural aged cheese types from various countries and determine whether a unique sensory characteristic exists within specific countries for European cheeses. The flavor of 152 cheeses from Estonia, France, Italy, Germany, Holland, Austria, England, Greece, Ireland, Spain, Switzerland, Sweden, Belgium, and Denmark were described during 4 independent studies. The sensory data from these studies were combined. The cheeses were sorted according to milk type and texture, and flavor characteristics of these groups were described. The main flavor characteristics of the cheeses tested were salty, sweet, sour, astringent, biting, pungent, sharp, nutty, musty/earthy, dairy fat, buttery, and dairy sweet. The cluster analysis divided the cheeses into 4 clusters: clusters 1 and 2 were sour, dairy sour, salty, astringent, biting, and varied in buttery (cluster 1) and sharp notes (cluster 2). Cluster 1 and 2 were mainly composed of French cheeses, while clusters 3 and 4 represented cheeses from various countries. Cluster 3 and 4 were sweet, with cooked milk and nutty characteristics and varied from buttery (cluster 3) to sharp notes (cluster 4). Cheeses from some countries, for example, France and Estonia, generally exhibited common sensory characteristics within the specific country, but cheeses from some other countries, such as Italy, varied widely, and seemed to have no common sensory theme. Most regional cheese standards are not specific about flavor profiles and these results suggest it may be possible to start a further characterization of cheeses in some countries.

축산물가공품에서 건조필름법과 TEMPO®TVC 검사법의 총세균수 비교분석

본 연구에서는 축산물가공품에서 건조필름법과 <TEX>$TEMPO^{(R)}$</TEX> TVC의 총세균수 측정에 대한 유효성을 평가하였다. 이를 위하여 국내 유통 중인 축산물가공품 257건과 대장균과 황색포도상구균을 인위적으로 접종시킨 축산물가공품 87건에서 대하여 총세균수를 측정하였다. 실험결과는 <TEX>$log_{10}$</TEX> 값으로 전환 후 CCFRA Guideline 29에 의하여 두 검사법간의 일치율을 분석하였고, Pearson의 검정법을 이용하여 상관분석을 실시하였다. 식육가공품 중 햄류, 건조저장육, 분쇄가공육제품 및 식육추출가공품에서 두검사법간 93%이상의 일치율이 확인된 반면 소시지류에서는 89.1%의 일치율을 보였다. 이에 반하여 우유류, 치즈류, 아이스크림류, 조제유류에서는 92% 이상의 일치율을 보였고, 알가열성형제품은 100%의 일치율을 보였다. 또한 소시지류(상관계수 <TEX>$r$</TEX> = 0.77)와 치즈류(상관계수 <TEX>$r$</TEX> = 0.89)를 제외한 축산물가공품 모든 유형에서 건조필름법과 <TEX>$TEMPO^{(R)}$</TEX> TVC 검사법간의 상관계수(<TEX>$r$</TEX>)가 0.9 이상으로 (<TEX>$P$</TEX> < 0.001) 높은 양의 상관관계를 나타내었다. 결론적으로 본 연구에서 <TEX>$TEMPO^{(R)}$</TEX> TVC는 검출한계가 있는 일부 축산물가공품을 제외하고 총세균수 검사에 있어서 효과적인 것으로 나타났다. We compared between an automated most-probable-number technique <TEX>$TEMPO^{(R)}$</TEX>TVC and traditional plating methods <TEX>$Petrifilm^{TM}$</TEX> for estimating populations of total aerobic bacteria in various livestock products. 257 samples randomly selected in local retail stores and 87 samples inoculated with <TEX>$E.$</TEX> <TEX>$coli$</TEX> ATCC 25922, <TEX>$Staphylococcus$</TEX> <TEX>$aureus$</TEX> ATCC 12868 were tested in this study. The degree of agreement was estimated according to the CCFRA (Campden and Chorleywood Food Research Association Group) Guideline 29 and the agreement indicates the difference of two kinds methods is lower than 1 log base 10(<TEX>$log_{10}$</TEX>). The samples of hams, jerky products, ground meat products, milks, ice creams, infant formulas, and egg heat formed products were showed above 95% in the agreement of methods. In contrast, proportion of agreement on meat extract products, cheeses and sausages were 93.1%, 92.1%, 89.1%, respectively. One press ham and five sausages containing spice and seasoning, two pork cutlets containing spice and bread crumbs, two meat extract product and two natural cheeses and one processing cheese with a high fat content, and one ice cream containing chocolate of all samples showed the discrepancy. Our result suggest that <TEX>$TEMPO^{(R)}$</TEX>TVC system is efficient to analyses total aerobic bacteria to compare manual method in time-consuming and laborious process except livestock products having limit of detection.

Metabolomics-based component profiling of hard and semi-hard natural cheeses with gas chromatography/time-of-flight-mass spectrometry, and its application to sensory predictive modeling

Gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS) was used to analyze hydrophilic low molecular weight components, including amino acids, fatty acids, amines, organic acids, and saccharides, in cheese, and the sensometric application for practical metabolomic studies in the food industry is described. Derivatization of target analytes was conducted prior to the GC/TOF-MS analysis. Data on 13 cheeses, six Cheddar cheeses, six Gouda cheeses and one Parmigiano-Reggiano cheese, were analyzed by multivariate analysis. The uniqueness of the Parmigiano-Reggiano cheese metabolome was revealed. Principal component analysis (PCA) showed no grouping of the Cheddar cheeses and Gouda cheeses according to production method or country of origin. The PCA loading plot confirms that many amino acids contribute positively to PC1, suggesting that PC1 is closely related to degradation of proteins, and that lactic acid contributed positively to PC2, whereas glycerol contributed negatively to PC2, suggesting that factors regarding degradation of carbohydrates and fats were expressed in PC2. Partial least squares (PLS) regression models were constructed to predict the relationship between the metabolite profile and two sensory attributes, "Rich flavor" and "Sour flavor", which were related to maturation. The compounds that play an important role in constructing each sensory prediction model were identified as 12 amino acids and lactose for "Rich flavor", and 4-aminobutyric acid, ornithine, succinic acid, lactic acid, proline and lactose for "Sour flavor". The present study revealed that metabolomics-based component profiling, focusing on hydrophilic low molecular weight components, was able to predict the sensory characteristics related to ripening.

Detection of milk powder and caseinates in Halloumi cheese

Halloumi cheese is traditionally manufactured from fresh milk. Nevertheless, dried dairy ingredients are sometimes illegally added to increase cheese yield. Lysinoalanine and furosine are newly formed molecules generated by heating and drying milk protein components. The levels of these molecular markers in the finished Halloumi have been investigated to verify their suitability to reveal the addition of skim milk powder and calcium caseinate to cheese milk. Because of the severe heating conditions applied in curd cooking, genuine Halloumi cheeses (n=35), representative of the Cyprus production, were characterized by levels of lysinoalanine (mean value=8.1 mg/100g of protein) and furosine (mean value=123 mg/100g of protein) unusual for natural cheeses. Despite the variability of the values, a good correlation between the 2 parameters (R=0.975) has been found in all cheeses, considering both the fresh and mature cheeses as well as those obtained from curd submitted to a prolonged cooking following a traditional practice adopted by a very small number of manufacturers. Experimental cheeses made by adding as low as 5% of skim milk powder, or calcium caseinate, or both, to cheese milk fell outside the prediction limits at ±2 standard deviation of the above-reported correlation regardless of curd cooking conditions or ripening length. This correlation may be adopted as a reliable index of Halloumi cheese genuineness.

DEVELOPMENT OF A FLAVOR LEXICON FOR PROCESSED AND IMITATION CHEESES

ABSTRACT In the U.S.A., the production of processed cheese (PC) totaled 1,014 million kg in 2005. These products are made using natural cheese (NC), but imitation products are also available. Functionality and meltability are primary characteristics of these products, but flavor also plays a role. Studies have not focused on the flavor of these products. This study was conducted to identify and define the sensory properties of PC and imitation cheese (Imi). Three dairy experts evaluated 55 PC and Imi for initial language development. Following language development and refinement, 26 PC and Imi were selected and evaluated in triplicate by an experienced sensory panel (n = 8). Data were evaluated by analysis of variance with Fisher's least significant difference for means separation and by principal component analysis. Eighteen aromatics and five basic tastes were documented in the products. PC products, which are made from NC, were characterized by sweet aromatic, cooked/milky, caramelized/toasted cheese, diacetyl, whey, milkfat and brothy flavors. Imis that had casein/caseinates were distinguished by minty flavors and Imis with other protein sources were differentiated by cardboard and oxidized/fatty flavors. This study demonstrated an array of flavor profiles among PC and between PC and Imi. This flavor lexicon can help the industry to better define and differentiate PC and Imi and ultimately to help better understand consumer flavor preferences for these products. PRACTICAL APPLICATIONS Processed cheese (PC) makes up a large market segment with processed cheese foods, spreads, and cold pack products and imitation products. These products are distinct from natural cheeses. This study established a defined descriptive flavor language for these products that can help cheese manufacturers understand the flavor profiles of different PC- and imitation cheese-type products.

Effect of Natural Cheese Characteristics on Process Cheese Properties

Natural cheese is the major ingredient utilized to manufacture process cheese. The objective of the present study was to evaluate the effect of natural cheese characteristics on the chemical and functional properties of process cheese. Three replicates of 8 natural (Cheddar) cheeses with 2 levels of calcium and phosphorus, residual lactose, and salt-to-moisture ratio (S/M) were manufactured. After 2 mo of ripening, each of the 8 natural cheeses was converted to 8 process cheese foods that were balanced for their composition, including moisture, fat, salt, and total protein. In addition to the standard compositional analysis (moisture, fat, salt, and total protein), the chemical properties (pH, total Ca, total P, and intact casein) and the functional properties [texture profile analysis (TPA), modified Schreiber melt test, dynamic stress rheometry, and rapid visco analysis] of the process cheese foods were determined. Natural cheese Ca and P, as well as S/M, significantly increased total Ca and P, pH, and intact casein in the process cheese food. Natural cheese Ca and P and S/M also significantly affected the final functional properties of the process cheese food. With the increase in natural cheese Ca and P and S/M, there was a significant increase in the TPA-hardness and the viscous properties of process cheese food, whereas the meltability of the process cheese food significantly decreased. Consequently, natural cheese characteristics such as Ca and P and S/M have a significant influence on the chemical and the final functional properties of process cheese.