Effect of added α-ketoglutaric acid,pyruvic acid or pyridoxal phosphate on proteolyis and quality of Cheddar cheese

Cheddar cheese curds were supplemented with 1, 5 or 20 g of α-ketoglutarate or pyruvic acid or 1.2 g pyridoxal-5¹-phosphate/kg cheese curd. The higher levels of keto-acids (5 or 20 g/kg curd) caused undesirable changes in the physico-chemical properties of resultant cheese. All levels of α-ketoglutarate reduced the pH of the cheese and promoted syneresis during pressing, while pyruvic acid increased the pH of the cheese. The numbers of starter and non-starter lactic acid bacteria were not affected by the addition of keto-acids or pyridoxal-5¹-phosphate. α-Ketoglutarate or pyruvic acid, at 1 g/kg, or pyridoxal-5¹-phosphatase, at 1.2 g/kg cheese curd, did not influence primary proteolysis in the cheese. The highest and lowest concentrations of total and individual free amino acids were found in the cheeses treated with pyruvic acid or α-ketoglutarate, respectively. The concentrations of most amino acids were lower in the cheeses treated with pyridoxal-5¹-phosphate than in the control. The results of this study suggest that α-ketoglutarate and pyridoxal-5¹-phosphate enhanced the degradation of most amino acids in Cheddar cheese while pyruvic acid promoted the formation of amino acids. The cheeses treated with α-ketoglutarate were more mature than the control cheese of the same age while pyruvic acid-treated cheese had a better flavour than the control.     

Probiotic Cheddar Cheese: Influence of Ripening Temperatures on Proteolysis and Sensory Characteristics of Cheddar Cheeses

ABSTRACT:  Bifidobacterium longum 1941, B. animalis subsp. lactis LAFTI^® B94, Lactobacillus casei 279, Lb. casei LAFTI L26, Lb. acidophilus 4962, or Lb. acidophilus LAFTI L10 were used as an adjunct in the production of Cheddar cheeses, which were ripened at 4 and 8 °C for 24 wk. Effects of ripening temperatures and probiotic adjuncts on proteolysis and sensory evaluation of the cheeses were examined. Higher ripening temperature increased the level of proteolysis in the cheeses. Product of proteolysis and organic acids released during ripening were shown to be important for the flavor of Cheddar cheeses. There were positive and significant correlations between the levels of soluble nitrogen, lactic, acetic, and butyric acids, percentage hydrolysis of α_s1-CN and β-CN to the scores of cheddary flavor ( P < 0.05). Scores for sour-acid and vinegary flavors were higher in cheeses with the addition of Bifidobacterium sp. or Lb. casei 279 ripened at 8 °C. The scores were positively and significantly correlated to the level of lactic, acetic, and free amino acids in the cheeses ( P < 0.05). The results show that both 4 and 8 °C have potential for use in the ripening of probiotic Cheddar cheeses.     

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.     

Evolution of Free Amino Acids during the Ripening of Cheddar Cheese Containing Added Lactobacilli Strains

Cheddar cheese was produced with different lactobacilli strains added to accelerate ripening. The concentration of proteolytic products was determined as free amino acids in the water-soluble fraction at two, four, seven and nine months of aging and at two different maturation temperatures (6°C, 15°C). All amino acids increased during ripening and were higher in the Lactobacillus- added cheeses than in the control cheese, and higher in cheeses ripened at 15°C than at 6°C. Glutamic acid, leucine, phenylalanine, valine and lysine were generally in higher proportion in all cheeses. The cheeses with added L. casei-casei L2A were classified as having a “strong Cheddar cheese” flavor after only seven months of ripening at 6°C.     

Objective assessment of cheddar cheese quality

Chemical and physical analyses of cheese are required to objectively assess cheese ripening. Statistical Multivariate Analysis of HPLC and free amino acid data for each of 60 Cheddar cheeses, varying in age and quality, were used to objectively classify the cheeses according to maturity, flavour quality (defective or not) and texture. Additional information was obtained from compositional analysis and gel electrophoresis. The total concentration of free amio acids was more effective than HPLC analysis for discriminating between mild, mature and extra-mature Cheddar cheeses whereas HPLC discriminated more effectively between defective and non-defective.     

Comparison of different bacterial culture systems for the production of reduced-fat Cheddar cheese

Six different culture systems, two controls (A and B) containing mesophilic starter lactococci and four experimental systems (C, D, E and F) containing mesophilic lactococci plus adjunct cultures (all of which contained Lactobacillus helveticus ), were compared for their effects on the quality of reduced-fat Cheddar cheese (175 g/kg fat). Adjunct cultures (i.e. C, D and F) resulted in cheeses having significantly higher concentrations of low molecular mass peptides (i.e. < 0.5 kDa) and free amino acids than the control cheeses. The adjunct cultures D and F resulted in cheeses that received higher flavour scores and were more acceptable than the control cheeses at 90 and 180 days.     

Characterization of aromatic properties of old-style cheese starters

Old-style cheese starters were evaluated to determine their ability to produce cheese aroma compounds. Detailed analyses of the aroma-producing potential of 13 old-style starter cultures were undertaken. The proteolytic profile of the starters was established by an accelerated ripening study using a model cheese slurry and compared with those of a commercial aromatic starter and commercial Cheddar cheeses. To evaluate the aromatic potential of the starter cultures, quantification of free amino acids liberated and volatile compounds after 15 d of ripening at 30°C as well as sensory analysis were carried out. Results showed that proteolysis patterns of all 13 starter cultures in the curd model were comparable to those of commercial Cheddar cheeses. All tested cultures demonstrated the ability to produce high amounts of amino acids recognized as precursors of aroma compounds. Several differences were observed between the starters and commercial Cheddar cheeses regarding some amino acids such as glutamate, leucine, phenylalanine, proline, and ornithine, reflecting the various enzymatic systems present in the starters. Starters Bt (control) and ULAAC-E exhibited various significant differences regarding their free amino acid profiles, as confirmed by sensory analysis. In addition, identification of volatile compounds confirmed the presence of several key molecules related to aroma, such as 3-methylbutanal and diacetyl. Besides the aroma-producing aspect, 2 starters (ULAAC-A and ULAAC-H) seem to possess an important ability to generate large amounts of γ-aminobutyric acid, which contributed up to 15% of the total amino acids present in the model curd after 15 d ripening. γ-Aminobutyric acid is an amine well-known for its antihypertensive and calming effects.     

Analysis of cheese for histamine, tyramine, tryptamine, histidine, tyrosine, and tryptophane

A method is described for determining the content of selected biologically active amines (histamine, tyramine, tryptamine) and amino acids (histidine, tyrosine, tryptophane) in cheeses by high performance liquid chromatography. The amines and amino acids were quantified by employing a counter ion-containing mobile phase and by comparing peak areas of high performance liquid chromatography charts for sample cheeses versus standard cheeses containing known amounts of added amines based on dual injections of samples and standards. Recovery of amines and amino acids varied from 87.5 to 111%. Histamine, which has been associated with food poisoning in concentrations of 185 mg/100 g in Swiss cheese and 180 to 500 mg/100 g in fish, was found in concentrations above 500 mg/100 g in Swiss cheese. The high performance liquid chromatography analytical method should be useful for screening to detect cheese samples containing toxic amounts of histamine and for research studies designed to determine the cause and effect relationships for histamine production in cheese.     

Texture, proteolysis and viable lactic acid bacteria in commercial cheddar cheeses treated with high pressure

High pressure processing was investigated for controlling Cheddar cheese ripening. One-month-or 4-month-old Cheddar cheeses were subjected to pressures ranging from 200 to 800 MPa for 5 min at 25 C. The number of viable Lactococcus lactis (starter) and Lactobacillus (nonstarter) cells decreased as pressure increased. Subsequent storage of the control and pressure-treated cheeses at 10 degrees C caused viable cell counts to change in some cases. Free amino acid content was monitored as an indicator of proteolysis. Cheeses treated with pressures > or = 400 MPa evolved free amino acids at significantly lower rates than the control. No acceleration in free amino acid development was observed at lower pressures. Pressure treatment did not accelerate the rate of textural breakdown compared with the non-pressure treated control. On the contrary, pressure treatment at 800 MPa reduced the time-dependent texture changes. Results indicate that high pressure may be useful in arresting Cheddar cheese ripening.     

Accelerated Cheddar Cheese Ripening by Added Microbial Enzymes

Good quality medium sharp Cheddar cheeses with 3-mo curing at 10 C were produced when the following enzyme combinations and concentrations were used: fungal protease 31000 (Miles), .005% + fungal lipase-MY (Meito) .00005 to .0002%; and fungal protease P-53 (Rohm & Haas), .0035% + fungal lipase-MY (Meito), .00005 to .0002%.Cheddar cheeses treated with microbial enzymes developed higher soluble protein and free volatile fatty acids and displayed better flavor and greater acceptability than control cheeses. Added microbial proteases contributed to the breakdown of casein, especially β-casein. Also, αs₁-I casein and free amino acids were high in cheeses treated with protease. Increased rate of proteolysis in enzyme-treated cheese had a direct relation to accelerated ripening.     

Study of taste-active compounds in the water-soluble extract of mature Cheddar cheese

The chemical composition of the water-soluble extracts of mature Cheddar cheese were identified, with the emphasis on understanding the interplay of compounds contributing to the savoury taste in Cheddar. The ultra-filtered water-soluble extracts of two mature Cheddar cheeses were fractionated by gel permeation chromatography (GPC). By sensory evaluation, two taste-active GPC fractions were identified from each cheese. On the basis of chemical profiling of these fractions, aqueous model tastant mixtures were prepared and sensory omission tests carried out. Glutamic acid, organic acids and mineral salts were the main tastants, whereas the other amino acids had a limited impact on taste. The characteristic umami taste was explained by a synergistic effect of glutamic acid and salts. Matching umami taste intensities were obtained from different concentrations of glutamic acid and salts. Unmasking of a bitter or sweet taste from mixtures of sub-threshold concentrations of amino acids without glutamic acids was also observed.     

Effect of curd washing on cheese proteolysis,texture, volatile compounds,and sensory grading in full fat Cheddar cheese

Curd was washed to varying degrees during Cheddar cheese manufacture, by partial replacement of whey with water at the early stages of cooking, to give target levels of lactose plus lactic acid in cheese moisture of 5.3 (control), 4.5, 4.3 and 3.9% (w/w). The cheeses were matured at 8 °C for 270 days. While curd washing had little effect on composition or the mean levels of proteolysis (as measured by pH 4.6 soluble nitrogen and levels of free amino acids), it led to cheeses that were, overall, firmer and less brittle. Curd washing resulted in cheeses having lower levels of some volatile compounds, and being less acid, more buttery, sweeter, saltier and creamier than non-washed cheeses that had more 'sweaty', pungent and farmyard-like sensory notes. The results suggest that curd washing during Cheddar manufacture may be used as a means of creating variants with distinctive flavour profiles.     

Effect of microencapsulated ferrous sulfate particle size on Cheddar cheese composition and quality

Iron-fortified Cheddar cheese was manufactured with large microencapsulated ferrous sulfate (LMFS; 700–1,000 µm in diameter) or small microencapsulated ferrous sulfate (SMFS; 220–422 µm in diameter). Cheeses were aged 90 d. Compositional, chemical, and sensory characteristics were compared with control cheeses, which had no ferrous sulfate added. Compositional analysis included fat, protein, ash, moisture, as well as divalent cations iron, calcium, magnesium, and zinc. Thiobarbituric acid reactive species assay was conducted to determine lipid oxidation. A consumer panel consisting of 101 participants evaluated the cheeses for flavor, texture, appearance, and overall acceptability using a 9-point hedonic scale. Results showed 66.0% iron recovery for LMFS and 91.0% iron recovery for SMFS. Iron content was significantly increased from 0.030 mg of Fe/g in control cheeses to 0.134 mg of Fe/g of cheese for LMFS and 0.174 mg of Fe/g of cheese for SMFS. Fat, protein, ash, moisture, magnesium, zinc, and calcium contents were not significantly different when comparing iron-fortified cheeses with the control. Iron fortification did not increase lipid oxidation; however, iron fortification negatively affected Cheddar cheese sensory attributes, particularly the LMFS fortified cheese. Microencapsulation of ferrous sulfate failed to mask iron's distinct taste, color, and odor. Overall, SMFS showed better results compared with LMFS for iron retention and sensory evaluation in Cheddar cheese. Results of this study show that size of the microencapsulated particle is important in the retention of the iron in the cheese and its sensory attributes. This study provides new information on the importance of particle size with microencapsulated nutrients.     

Effect of proteolysis and calcium equilibrium on functional properties of natural cheddar cheese during ripening and the resultant processed cheese

The changes in proteolysis, calcium (Ca) equilibrium, and functional properties of natural Cheddar cheeses during ripening and the resultant processed cheeses were investigated. For natural Cheddar cheeses, the majority of the changes in pH 4.6 soluble nitrogen as a percentage of total nitrogen (pH 4.6 SN/TN) and the soluble Ca content occurred in the first 90 d of ripening, and subsequently, the changes were slight. During ripening, functional properties of natural Cheddar cheeses changed, that is, hardness decreased, meltability was improved, storage modulus at 70 °C (G'T=70) decreased, and the maximum tan delta (TDmax) increased. Both pH 4.6 SN/TN and the soluble Ca were correlated with changes in functional properties of natural Cheddar cheeses during ripening. Kendall's partial correlation analysis indicated that pH 4.6 SN/TN was more significantly correlated with changes in hardness and TDmax. For processed cheeses manufactured from natural Cheddar cheeses with different ripening times, the soluble Ca content did not show significant difference, and the trends of changes in hardness, meltability, G'T=70, and TDmax were similar to those of natural Cheddar cheeses. Kendall's partial correlation analysis suggested that only pH 4.6 SN/TN was significantly correlated with the changes in functional properties of processed cheeses.     

Viscoelastic Properties of Cheddar Cheese: Effect of Calcium and Phosphorus,Residual Lactose,Salt-to-Moisture Ratio and Ripening Time

The viscoelastic properties of eight different types of Cheddar cheeses prepared with two levels of calcium (Ca) and Phosphorus (P) content, two levels of residual lactose content and two levels of salt to moisture ratio (S/M) ratio were studied in a STRESSTECH viscoanalyzer. The elastic (G′) and viscous (G″) modulus were measured at 0, 1, 2, 4, 6, and 8 months of ripening during heating the cheese samples from 30 to 70°C. Low levels of Ca and P content (0.53 g Ca and 0.39 g P /100 g cheese) in the Cheddar cheese resulted up to 20.9% and 15.9% lower elastic and viscous modulus respectively, compared to Cheddar cheese prepared with high levels of Ca and P content (0.67 g Ca and 0.53 g P/100g cheese) during ripening up to 8 months. Low levels of residual lactose (0.78 g/100g) in the Cheddar cheese resulted in 39.1 and 78.1% lower elastic and viscous modulus, respectively, compared to Cheddar cheese with high levels of residual lactose (1.4 g/100g) during ripening up to 8 months. In the same way, low levels of S/M ratio (4.8) in the Cheddar cheese resulted in 40.7 and 40.5% lower elastic and viscous modulus, respectively, compared to high levels of S/M ratio (6.4) during ripening up to 8 months. Upon heating from 30 to 70°C, the elastic and viscous modulus of the eight different types of Cheddar cheeses reduced up to 91.7 and 95.1%, respectively, during ripening. Cheddar cheese recorded maximum elastic modulus at the end of 8 months of ripening, and maximum viscous modulus at the end of 4 months of ripening.     

Influence of ripening temperature on the volatiles profile and flavour of Cheddar cheese made from raw or pasteurised milk

Cheddar cheeses were made from raw (R1, R8) or pasteurised (P1, P8) milk and ripened at 1°C (P1, R1) or 8°C (P8, R8). Volatile compounds were extracted from 6 month-old cheeses and analysed, identified and quantified by gas chromatography-mass-spectrometry. A detailed sensory analysis of the cheeses was performed after 4 and 6 months of ripening. The R8 cheeses had the highest and P1 the lowest concentrations of most of the volatile compounds quantified (fatty acids, ketones, aldehydes, esters, alcohols, lactones and methional). The R8 and P8 cheeses contained higher levels of most of the volatiles than R1 and P1 cheeses. Ripening temperature and type of milk influenced most of the flavour and aroma attributes. Principal component analysis (PCA) of aroma and flavour attributes showed that P1 and R1 had similar aroma and flavour profiles, while R8 had the highest aroma and flavour intensities, highest acid aroma and sour flavour. The age of cheeses influenced the perception of creamy/milky and pungent aromas. PCA of the texture attributes separated cheeses on the basis of ripening temperature. The R8 and P8 cheeses received significantly higher scores for perceived maturity than P1 and R1 cheeses. The P1 and R1 cheeses had similar values for perceived maturity. In a related study, it was found that concentrations of amino acids and fatty acids were similar in R1 and P1 during most of the ripening period, and R1 and P1 cheeses had low numbers of non-starter lactic acid bacteria (NSLAB). The panel found that ripening temperature, type of milk and age of cheeses did not influence the acceptability of cheese. It is concluded that NSLAB contribute to the formation of volatile compounds and affect the aroma and flavour profiles and the perceived maturity of Cheddar cheese.