Variation in organic acids content during ripening of pickled white cheese

Nine organic acids (formic, pyruvic, lactic, acetic, orotic, citric, uric, propionic, and butyric) were analyzed during ripening of pickled White cheese for 12 mo by high-performance liquid chromatography with a reverse phase C18 (120x 5-mm) column and UV detector. The level oftotal organic acids showed an increase along the ripening period, but its composition varied during the process. Initially, lactic acid accounted for 95% of the total, after 9 and 12 mo of ripening, butyric acid constituted 20 and 27% of the total, respectively. Each organic acid presented a characteristic pattern of change during ripening. Discriminant analysis classified cheeses according to their age. Stepwise regression analysis allowed estimation of the ripening time of samples according to their organic acid levels.     

Freezing low moisture Mozzarella cheese: changes in organic acid content

Vacuum-packaged low moisture Mozzarella cheese samples were ripened both by the traditional method at 4°C and after subjecting the samples to a freeze (−20°C)–thaw (4°C) cycle before ageing. Nine organic acids (formic, pyruvic, orotic, uric, lactic, acetic, citric, propionic and butyric) were analyzed each week by high performance liquid chromatography. There was no significant effect of the freeze–thaw cycle on the variations in organic acids content. They were only affected by ripening time. Each organic acid presented a characteristic pattern of change during ripening. Discriminant analysis classified cheeses according to their age.     

Effect of a commercial adjunct culture on organic acid contents of low-fat Feta-type cheese

The effect of a commercial adjunct culture (CR-213, containing Lactococcus lactis subsp. cremoris and Lactococcus lactis susp. lactis and added at the level of 0.6 g kg⁻¹ or 0.9 g kg⁻¹ cheese milk) on the organic acid (OA) content of low-fat Feta-type cheese was studied. Full-fat (∼220 g kg⁻¹) and a low-fat (∼70 g kg⁻¹) cheeses were used as controls. The main OA of all cheeses throughout ripening were lactic, citric and acetic acids. The effect of ripening time was significant (P < 0.05) for all OA but treatments did not affect acetic, succinic and uric acids. Cheeses with lower fat content were found to contain significantly (P < 0.05) more lactic and citric but less butyric acid than the full-fat control. The addition of the adjunct culture had a positive effect on butyric acid, propionic acid and acetoin content. The use of the adjunct culture could enhance the production of OA in low-fat Feta-type cheeses with eventual positive effect on their sensory properties.     

Effects of frozen and refrigerated storage on organic acid profiles of goat milk plain soft and Monterey Jack cheeses

The effects of 6 mo of freezing and refrigeration on organic acid profiles of 2 types of goat milk cheese [plain soft (PS) and Monterey Jack (MJ)] were studied in comparison with those of a nonfrozen control (NFC). Three lots of commercial PS cheeses were purchased, and 3 lots of MJ cheeses were manufactured at the University dairy plant. Each lot of the 2 types of cheeses was subdivided into 4 equal portions, and one subsample of each cheese was immediately stored at 4°C as the NFC for 0, 14, and 28 d. The other 3 were immediately frozen (−20°C) for 0, 3, and 6 mo (0MF, 3MF, and 6MF) and subsequently thawed the next day at 4°C. The samples were then stored at 4°C for 0, 14, and 28 d. Organic acids were quantified using an HPLC. The PS had no pyruvic acid, and MJ contained no isotartaric acid; however, several unknown large peaks appeared between propionic and butyric acids. Differences in organic acid contents between PS and MJ cheeses were significant for all acids except citric and lactic acid. Lot effect was significant for most of the known acids, indicating that variations existed in milk composition and manufacturing parameters. Effects of storage treatments (NFC, 0MF, 3MF, and 6MF) were significant for most organic acids, except for orotic and a few unidentified acids. Aging at 4°C for 4 wk had little influence on all organic acids, except butyric acid. Concentrations of butyric, lactic, propionic, tartaric, and uric acids were significantly elevated as the frozen storage period advanced. At the initial stage, there were no differences in pH and acid degree values between NFC and frozen-stored groups of both cheeses. However, acid degree values gradually increased as the refrigerated storage extended up to 4 wk, indicating that lipolysis increased as the refrigeration storage at 4°C advanced. Although levels of several organic acids were changed in the goat cheeses, the prolonged frozen storage, up to 6 mo, was apparently feasible for extending storage.     

The effect of different packaging methods on the formation of biogenic amines and organic acids in Kashar cheese

The effects of packaging methods (nonvacuum and vacuum) on biogenic amines (cadaverine, putrescine, tyramine, tryptamine, phenylethylamine, and histamine) and organic acids (citric, lactic, formic, acetic, propionic, and butyric) during storage for 180 d at 4°C were investigated in Kashar cheese. Dry matter, titratable acidity, total nitrogen, water-soluble nitrogen, trichloroacetic acid-soluble nitrogen, phosphotungstic acid-soluble nitrogen, free amino group (proteolysis), pH, fat, and acid degree value were also determined. Storage period had a significant effect on all of the biogenic amines. When compared with vacuum packaging, nonvacuum packaging resulted in no large differences among the amounts of biogenic amines. Vacuum-packaged cheeses had more lactic, formic, acetic, and butyric acids than did cheeses packaged without vacuum. Water-soluble nitrogen, trichloroacetic acid-soluble nitrogen, phosphotungstic acid-soluble nitrogen, proteolysis, pH, and acid degree values of the cheese samples increased continuously until the end of the ripening in all the samples. No significant change was observed in total nitrogen, dry matter, or fat content within the ripening period, whereas titratable acidity values changed significantly in vacuum-packaged cheese and decreased slightly in the non-vacuum-packaged cheeses. The results of this study showed that storage period and packaging method had significant effects on the quality of Kashar cheese.     

Proteolysis in goat cheese made from raw,pasteurized or pressure-treated milk

Primary and secondary proteolysis of goat cheese made from raw (RA), pasteurized (PA; 72 °C, 15 s) and pressure-treated milk (PR; 500 MPa, 15 min, 20 °C) were examined by capillary electrophoresis, nitrogen fractionation and HPLC peptide profiles. PA milk cheese showed a more important hydrolysis (P<0.05) of α_s1-casein than RA milk cheese at the first stages of ripening (15 days), while PR milk cheese had a level between those seen in PA and RA milk cheeses. Degradation of β-casein was more important (P<0.05) in PA and PR than in RA milk cheeses at 15 days of ripening. However, from thereon β-casein in PR and RA milk cheeses was hydrolyzed at essentially similar rates, but at lower rates (P<0.05) than in PA milk cheeses. Pressure treatment could induce proteolysis of β-casein in a way, which is different from that produced by heat treatment. There was an increase in 4.6-soluble nitrogen (WSN) and in trichloroacetic acid (TCASN) throughout ripening in cheeses, but higher contents (P<0.05) in PA and PR milk cheeses at the end of ripening were observed. PR milk cheeses contained considerably higher content (P<0.05) of free amino acids than RA or PA milk cheeses. In general, heat and pressure treatments had no significant effect on the levels of hydrophobic and hydrophilic peptides.     

Influence of calcium and phosphorus, lactose, and salt-to-moisture ratio on Cheddar cheese quality: changes in residual sugars and water-soluble organic acids during ripening

Cheddar cheese ripening involves the conversion of lactose to glucose and galactose or galactose-6-phosphate by starter and nonstarter lactic acid bacteria. Under ideal conditions (i.e., where bacteria grow under no stress of pH, water activity, and salt), these sugars are mainly converted to lactic acid. However, during ripening of cheese, survival and growth of bacteria occurs under the stressed condition of low pH, low water activity, and high salt content. This forces bacteria to use alternate biochemical pathways resulting in production of other organic acids. The objective of this study was to determine if the level and type of organic acids produced during ripening was influenced by calcium (Ca) and phosphorus (P), residual lactose, and salt-to-moisture ratio (S/M) of cheese. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), lactose at pressing (2.4 vs. 0.78%), and S/M (6.4 vs. 4.8%) were manufactured. The cheeses were analyzed for organic acids (citric, orotic, pyruvic, lactic, formic, uric, acetic, propanoic, and butyric acids) and residual sugars (lactose, galactose) during 48 wk of ripening using an HPLC-based method. Different factors influenced changes in concentration of residual sugars and organic acids during ripening and are discussed in detail. Our results indicated that the largest decrease in lactose and the largest increase in lactic acid occurred between salting and d 1 of ripening. It was interesting to observe that although the lactose content in cheese was influenced by several factors (Ca and P, residual lactose, and S/M), the concentration of lactic acid was influenced only by S/M. More lactic acid was produced in low S/M treatments compared with high S/M treatments. Although surprising for Cheddar cheese, a substantial amount (0.2 to 0.4%) of galactose was observed throughout ripening in all treatments. Minor changes in the levels of citric, uric, butyric, and propanoic acids were observed during early ripening, whereas during later ripening, a substantial increase was observed. A gradual decrease in orotic acid and a gradual increase in pyruvic acid content of the cheeses were observed during 12 mo of ripening. In contrast, acetic acid did not show a particular trend, indicating its role as an intermediate in a biochemical pathway, rather than a final product.     

High Performance Liquid Chromatographic Determination of Organic Acids in Dairy Products

A simple isocratic HPLC technique was developed for the quantitative analysis of organic acids in dairy products. An Ammex HPX- 87 column at 65°C, 0.0090N H₂SO₄ mobile phase and UV detection at 220 and 275 nm were utilized. Orotic, citric, pyruvic, lactic, uric, formic, acetic, propionic, butyric, and hippuric acids were quantitated for whole milk, skim powder, cultured buttermilk, sour cream, cottage cheese, yogurt, sharp Cheddar cheese, and blue cheese. Over 90% recoveries of acids added to whole milk were observed for ail acids except butyrid; the average recovery for butyric was 86%.     

Specific effect of high-pressure treatment of milk on cheese proteolysis

The extent of primary and secondary proteolysis of cheeses made from raw (RA), pasteurized (PA, 72 degrees C, 15 s) or pressure-treated (PR, 500 MPa, 15 min, 20 degrees C) goats' milk was assessed. Modifications in cheese-making technology were introduced to obtain cheeses with the same moisture content, and thus studied per se the effect of milk treatment on cheese proteolysis.The PR milk cheese samples were differentiated from RA and PA milk cheeses by their elevated beta-lg content, and by the faster degradation of alphas1-, alphas2- and beta-CN throughout ripening. Non-significant differences were found in either pH 4.6 soluble-nitrogen or trichloracetic acid soluble-nitrogen contents of cheeses. However, the pasteurization of milk decreased the free amino acid production in cheese. The RA milk cheeses had the highest amount of proline and the lowest concentrations of serine, tyrosine, arginine and alpha-aminobutyric acid, whereas PR milk cheese showed higher levels of arginine.     

Rapid simultaneous determination of organic acids,free amino acids,and lactose in cheese by capillary electrophoresis

A capillary electrophoresis (CE) method for the simultaneous separation of 11 metabolically important organic acids (oxalic, formic, citric, succinic, orotic, uric, acetic, pyruvic, propionic, lactic, and butyric), 10 amino acids (Asp, Glu, Tyr, Gly, Ala, Ser, Leu, Phe, Lys, and Trp), and lactose has been optimized, validated, and tested in dairy products. Repeatability and linearity were calculated for each compound, with detection limit values as low as 0.2 x 10(-2) mM for citric acid and Gly. The method was applied to analyze yogurt and different varieties of commercial cheeses. This method yielded specific CE patterns for different varieties of cheese. Also, it has been shown to be sensitive enough to measure small changes in composition of some of those compounds in fresh cheese stored under accelerated ripening conditions for 2 d at 32 degrees C (e.g., from 1728.3 +/- 45.0 to 1166.7 +/- 4.5 mg/100 g of DM in the case of lactose, or from 23.5 +/- 0.6 to 76.8 +/- 16.7 mg/100 g of DM in the case of acetic acid).     

Changes in textural, microstructural, and colour characteristics during ripening of cheeses made from raw, pasteurized or high-pressure-treated goats’ milk

Goats’ milk cheeses were made from raw (RA), pasteurized (PA; 72°C, 15 s) or pressure-treated (PR; 500 MPa, 15 min, 20°C) milk to compare textural, microstructural, and colour characteristics in relation to ripening time. Texture, microstructure and colour were evaluated by uniaxial compression and stress relaxation tests, confocal laser scanning microscopy and Hunter colorimetry, respectively.Raw and PR cheeses were firmer and less fracturable than PA cheese, but differences became less notable toward the end of ripening. PA and PR cheeses were less cohesive than RA cheese. Although cheeses exhibited a loss of elastic characteristics with ageing, PR cheese showed the most elastic behaviour initially. Confocal laser scanning micrographs displayed PR cheese with a regular and compact protein matrix, with small and uniform fat globules resembling the structure of RA cheese. Finally, colour evaluation demonstrated significant differences between cheeses due to milk treatments and ripening time.     

Microbiological changes throughout ripening of goat cheese made from raw,pasteurized and high-pressure-treated milk

The bacteriological quality during ripening of raw (RA), pasteurized (PA; 72°C, 15 s) and pressure-treated (PR; 500 MPa, 20°C, 15 min) goat milk assessed by enumeration of total bacteria, psychrotrophic bacteria, Enterobacteriaceae, lactobacilli, enterococci, Micrococcaceae and lactococci was evaluated. The high pressure treatment applied was as efficient as pasteurization in reducing the bacterial population of milk. Experimental cheeses were made from RA, PA and PR milks to study the microbial population during ripening. Lactobacilli and lactococci were the predominant microbiota present during ripening in all the cheeses. There were no differences in numbers of starter bacteria during ripening. However, lactobacilli counts for RA milk cheese were significantly higher than for PA and PR cheeses in all the ripening stages studied. Micrococcaceae and enterococci remained at a secondary level, and no differences were observed between cheeses at the end of ripening. On the other hand, the number of Enterobacteriaceae decreased during ripening, but faster in PR milk cheese than in PA and RA milk cheeses. The results of this study suggest that goat cheese made from PR milk had similar microbiological characteristics to PA milk cheeses.     

Profiles of Organic Acid and Volatile Compounds in Acid-Type Cheeses Containing Herbs and Spices (Surk Cheese)

A study was conducted to evaluate the basic chemical composition, organic acids, volatile compound profiles, and overall acceptability of Surk cheese (acid cheese). The organic acids were determined by reverse phase high performance liqued chromatography method, and volatile compounds were analyzed by static headspace/gas chromatography/mass spectrometry technique. A total of 134 volatile compounds, including 42 esters, 40 terpenes, 15 alcohos, 11 free fatty acids, 6 ketones, 5 aldehydes, 4 alkenes, 4 phenyl propanoids, 3 phenolics, and 4 other compounds, were identified in the Surk cheeses. The main compounds were found to be carvacrol, γ-terpinene, p-cymene, hexanoic acid, octanoic acid, decanoic acid, butanoic acid, and eugenol. The mean total organic acid content of the Surk cheese was 1.71 g/100 g. The main organic acid in the Surk cheese was lactic acid (1067 mg/100 g), followed by acetic, propionic, oxalic, formic, citric, pyruvic, orotic, hippuric, and uric acids.     

Ripening of Cheddar cheese made from blends of raw and pasteurised milk

Cheddar cheeses were made from pasteurised milk (P), raw milk (R) or pasteurised milk to which 10 (PR10), 5 (PR5) or 1 (PR1) % of raw milk had been added. Non-starter lactic acid bacteria (NSLAB) were not detectable in P cheese in the first month of ripening, at which stage PR1, PR5, PR10 and R cheeses had 10⁴, 10⁵, 10⁶ and 10⁷ cfu NSLAB g⁻¹, respectively. After ripening for 4 months, the number of NSLAB was 1–2 log cycles lower in P cheese than in all other cheeses. Urea–polyacrylamide gel electrophoretograms of water-soluble and insoluble fractions of cheeses and reverse-phase HPLC chromatograms of 70% (v/v) ethanol-soluble as well as -insoluble fractions of WSF were essentially similar in all cheeses. The concentration of amino acids were pro rata the number of NSLAB and were the highest in R cheese and the lowest in P cheese throughout ripening. Free fatty acids and most of the fatty acid esters in 4-month old cheeses were higher in PR1, PR5, PR10 and R cheeses than in P cheese. Commercial graders awarded the highest flavour scores to 4-month-old PR1 cheeses and the lowest to P or R cheese. An expert panel of sensory assessors awarded increasingly higher scores for fruity/sweet and pungent aroma as the level of raw milk increased. The trend for aroma intensity and perceived maturity was R>PR10>PP5>PR1>P. The NSLAB from raw milk appeared to influence the ripening and quality of Cheddar cheese.     

Simultaneous Determination of Sugars and Organic Acids in Cheddar Cheese by High-Performance Liquid Chromatography

In a simple, rapid isocratic HPLC method sugars and organic acids were separated on an Aminex HPX-87 column in the H⁺ form and detected using ultraviolet and refractive index detectors in series. Sugars (lactose, glucose and galactose) and acids (orotic, citric, pyruvic, lactic, uric, formic, acetic, propionic, butyric and hippuric) were identified by retention times. This method affords a simple technique for monitoring starter culture activity and following quality changes during cheese maturation.     

Determination of Organic Acids in Dairy Products by High Performance Liquid Chromatography

A high performance liquid chromatographic method was developed for the quantitative analysis of organic acids in dairy products. A reverse-phase C8 column at room temperature, a mobile phase of 0.5% w/v buffer ((NH₄)₂HPO₄ at pH 2.24 with H₃, PO₄)-0.4% v/v acetonitrile, UV detection at 214 nm and 1.2 mL/min flow rate were utilized. Formic, acetic, pyruvic, propionic, uric, orotic, citric, lactic and butyric acids were quantitated for raw milk, yogurt, Blue, Provolone, Port Salut and Quartirolo cheeses. Recoveries greater than 85.3% were observed for all acids.     

Application of Fourier transform infrared spectroscopy for monitoring short-chain free fatty acids in Swiss cheese

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 (∼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.     

发酵前后甜石榴汁中有机酸的变化研究

本试验利用反相液相色谱（RP-HPLC）法分离测定发酵前后甜石榴汁中有机酸种类和含量。在甜石榴汁中检测到的有机酸包括草酸、苹果酸、α-酮戊二酸、乳酸、乙酸、柠檬酸与富马酸,其中主要有机酸为乳酸（占总有机酸的51.2%）、草酸（占总有机酸的26.8%）和柠檬酸（占总有机酸的16.8%）。发酵后甜石榴汁中的草酸与乳酸含量下降,乙酸含量增加,新生成酒石酸、丙酮酸与琥珀酸;苹果酸与柠檬酸含量增加。发酵后甜石榴汁的有机酸总量下降了7.8%.     

Effect of milk centrifugation and incorporation of high heat-treated centrifugate on the microbial composition and levels of volatile organic compounds of Maasdam cheese

Centrifugation is a common milk pretreatment method for removal of Clostridium spores which, on germination, can produce high levels of butyric acid and gas, resulting in rancid, gassy cheese. The aim of this study was to determine the effect of centrifugation of milk, as well as incorporation of high heat-treated centrifugate into cheese milk, on the microbial and volatile profile of Maasdam cheese. To facilitate this, 16S rRNA amplicon sequencing in combination with a selective media-based approach were used to study the microbial composition of cheese during maturation, and volatile organic compounds within the cheese matrix were analyzed by HPLC and solid-phase microextraction coupled with gas chromatography–mass spectrometry. Both culture-based and molecular approaches revealed major differences in microbial populations within the cheese matrix before and after warm room ripening. During warm room ripening, an increase in counts of propionic acid bacteria (by ～10^1.5 cfu) and nonstarter lactic acid bacteria (by ～10⁸ cfu) and a decrease in the counts of Lactobacillus helveticus (by ～10^2.5 cfu) were observed. Lactococcus species dominated the curd population throughout ripening, followed by Lactobacillus, Propionibacterium, and Leuconostoc, and the relative abundance of these accounted for more than 99% of the total genera, as revealed by high-throughput sequencing. Among subdominant microflora, the overall relative abundance of Clostridium sensu stricto was lower in cheeses made from centrifuged milk than control cheeses, which coincided with lower levels of butyric acid. Centrifugation as well as incorporation of high heat-treated centrifugate into cheese milk seemed to have little effect on the volatile profile of Maasdam cheese, except for butyric acid levels. Overall, this study suggests that centrifugation of milk before cheesemaking is a suitable method for controlling undesirable butyric acid fermentation without significantly altering the levels of other volatile organic compounds of Maasdam cheese.     

Probiotic Cheddar cheese: Influence of ripening temperatures on survival of probiotic microorganisms, cheese composition and organic acid profiles

Bifidobacterium longum 1941, Bifidobacterium animalis subsp. lactis LAFTI^®B94 (B94), Lactobacillus casei 279, Lb. casei LAFTI^®L26 (L26), Lactobacillus acidophilus 4962 or Lb. acidophilus LAFTI^®L10 (L10) were used as an adjunct in the production of Cheddar cheeses which were ripened for 24 wk at 4 and 8 °C. Effects of ripening temperatures on survival of starter lactococci and probiotic microorganisms, pH and composition of cheeses and production of organic acids were examined. The counts of starter lactococci in cheeses produced with B. animalis B94, Lb. casei L26 or Lb. acidophilus 4962 ripened at 8 °C were significantly lower than those ripened at 4 °C (P < 0.05) at 24 wk. Probiotic microorganisms remained viable (>7.50 log₁₀ CFU/g) at the end of 24 wk and their viability was not affected by the ripening temperatures. There were significant effects of the type of probiotic microorganisms used, ripening time, ripening temperatures and their interactions on the concentration of lactic and acetic acids in the cheeses (P < 0.05). The acetic acid concentration in cheeses made with Bifidobacterium sp. or Lb. casei sp. was significantly higher than that of the control cheese (P < 0.05). Citric, propionic and succinic acids contents of the cheeses were not significantly affected by the type of probiotic microorganisms or ripening temperatures (P > 0.05).