Effect of a bacteriocin-producing Lactococcus lactis strain and high-pressure treatment on the esterase activity and free fatty acids in Hispánico cheese

The effect of milk inoculation with a bacteriocin-producing (BP) culture and of high-pressure (HP) treatment of 15-day-old Hispánico cheeses (400 MPa, 5 min, 10 °C), separately or combined, on the release of intracellular esterases and cheese lipolysis was investigated. Esterase activity and free fatty acids (FFAs) content increased during ripening of Hispánico cheese and palmitic, oleic and stearic acids being the most abundant FFAs. On day 15, the highest esterase activity was recorded for HP-treated BP cheese. The activity for HP-untreated BP cheese was the next highest. No difference in the activities was found between HP-treated and untreated cheeses made without BP culture. Total FFAs on day 15 were at a lower concentration in BP cheeses than in cheeses made without BP culture, probably due to the lower pH values of the former. The rate of total FFA accumulation from day 15 to day 50 was higher in BP cheeses (31.1–32.1% increase) than in cheeses made without BP culture (19.3–21.7% increase). The highest total FFA concentration on day 50 (612 mg kg⁻¹) was found for HP-untreated cheese made without BP culture.     

Effect of high-pressure treatments on proteolysis and texture of ewes’ raw milk La Serena cheese

La Serena cheeses, made from Merino ewes’ raw milk, were high-pressure (HP)-treated at 300 or 400 MPa for 10 min at 10 °C, on days 2 or 50 of ripening. Cheeses treated by HP on day 2 showed higher pH values than control cheese on day 3, but cheeses treated by HP on days 2 or 50 and control cheese had similar pH values on day 60. Breakdown of caseins was delayed by HP treatment of cheeses on day 2. Cheeses treated by HP on day 2 showed higher levels of hydrophilic peptides, lower levels of hydrophobic peptides, lower hydrophobic peptides: hydrophilic peptides ratios, and higher total contents of free amino acids than those of control cheese. HP treatment of cheese on day 50 scarcely affected proteolysis of 60-day-old cheeses. Fracturability, hardness and elasticity values of cheeses treated by HP on day 2 were higher than those of control cheese and of cheeses treated on day 50. Cheeses treated at 400 MPa on day 2 received the lowest scores for quality of taste from panellists, whereas the rest of HP-treated cheeses did not differ from control 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.     

Proteolysis during ripening of Manchego cheese made from raw or pasteurized ewes' milk. Seasonal variation

Changes in nitrogen compounds during ripening of 40 batches of Manchego cheese made from raw milk (24 batches) or pasteurized milk (16 batches) at five different dairies throughout the year were investigated. After ripening for six months, degradation of p-kappa- and beta-caseins was more intense in raw milk cheese and degradation of alpha(s2)-casein in pasteurized milk cheese. Milk pasteurization had no significant effect on breakdown of alpha(s1)-casein. Hydrophobic peptide content did not differ between raw and pasteurized milk cheese, whereas hydrophilic peptide content was higher in raw milk cheese. There were no significant differences between seasons for residual caseins, but hydrophobic peptides were at a higher level in cheese made in autumn and winter and hydrophilic peptides in cheese made in winter and spring. Raw milk cheese had a higher content of total free amino acids and of most individual free amino acids than pasteurized milk cheese. The relative percentages of the individual free amino acids were significantly different for raw milk and pasteurized milk cheeses. The relative percentages of Lys and lie increased, while those of Val, Leu and Phe decreased during ripening. There were also seasonal variations within the relative percentages of free amino acids. In raw milk cheeses, Asp and Cys were relatively more abundant in those made in autumn, Glu and Arg in cheeses made in winter, and Lys and Ile in cheeses made in spring and summer. Biogenic amines were detected only in raw milk cheese, with the highest levels of histamine, tryptamine and tyramine in cheeses made in spring, winter and spring, respectively.     

Proteolysis of Cheese Slurry Made from Pulsed Electric Field-Treated Milk

Raw milk cheeses have unique flavor and texture characteristics not obtainable in cheeses made from pasteurized milk. However, cheeses made from pasteurized milk are widespread, primarily for public health reasons. Pulsed electric field (PEF) treatment as a non-thermal pasteurization method has shown its ability to keep the flavor and natural characteristics of food samples intact, thus providing advantage over conventional heat processing. In this study, PEF treatment was performed in a continuous treatment chamber, consisting of two parallel stainless steel electrodes separated by a 50-mm-thick insulator. A 30-kV pulse generator was used to deliver bi-polar square waveform electric field to milk sample. Pulse width was 2 μs; pulse frequency was 2 Hz, and up to 120 pulses were applied. Cheese curds were made from raw milk, pasteurized milk, and PEF-treated milk, and their proteolysis processes were compared using curd slurry incubated at 30 °C for 5 days. The profiles of water-soluble peptides were measured using an reversed-phase high-performance liquid chromatography (RP-HPLC) system. The concentration of free amino acids was measured by Cd–ninhydrin method. Results indicated that PEF-treated milk has intermediate proteolysis profiles between raw milk and pasteurized milk in terms of peptide and free amino acid concentration. The results showed the potential of making high-quality cheeses by PEF treatment without sacrificing the natural characteristics of the cheeses.     

Changes of free amino acid content of Teleme cheese made with different types of milk and culture

The evolution of concentration of free amino acids in Teleme cheese made from sheep, goat or cow milk, using a thermophilic, mesophilic or a mixture of a thermophilic, a mesophilic culture throughout ripening was studied. The total free amino acid (TFAA) content increased at all stages of ripening, regardless of the milk and culture used. In general, the TFAA content was higher in cheeses made from cow’s milk than that of the cheeses made from ewe’s milk; cheese from goat’s milk ranged over intermediate levels. Also, higher concentrations of TFAA were found in cheeses made with the thermophilic than with the mesophilic culture. Cheeses made with the mixture of thermophilic–mesophilic culture ranged over intermediate levels. The results of this study have shown that Leu, Glu, Phe, Val and Lys were the major FAA of Teleme cheese at all stages of ripening, regardless of the type of milk and culture used.     

Changes in organic acids during ripening of cheeses made from raw, pasteurized or high-pressure-treated goats’ milk

Organic acids of cheeses made from raw (RA), pasteurized (PA; 72°C, 15 s) or pressure-treated (PR; 500 MPa, 15 min, 20°C) goats’ milk were qualitatively and quantitatively assessed during ripening. Nine organic acids (citric, pyruvic, malic, lactic, formic, acetic, uric, propionic and butyric) were analysed in each sample by HPLC.Milk treatment did not affect the total organic acids content of 1-day-old cheeses, which increased steadily from day 1 to day 60. At the end of ripening, RA and PR milk cheeses both exhibited higher concentration of organic acids than in those made from PA milk.Lactic acid was found in higher concentration in PR milk cheese from 30 days of ripening. The RA milk cheese, that showed the highest nonstarter lactic acid bacteria counts, were characterized by an elevated amount of propionic and acetic acids. These cheeses also were negatively correlated with both pyruvic and citric acid contents. The PA milk cheese showed a high level of malic acid, and was clearly differentiate from RA and PR milk cheeses by its low level of butyric acid.     

Study of the chemical composition,proteolysis, volatile compounds,and textural properties of industrial and traditional Beaten (Bieno sirenje) ewe milk cheese

The objective of this study was to determine the gross composition, proteolysis, and volatile and texture profiles during ripening of industrial (IND) and traditional (TRD) Beaten (Bieno sirenje) cheeses made by using ewe milk. In the course of the analyses, statistical differences were determined in some physicochemical parameters, nitrogen fractions, and total free amino acid levels between TRD and IND types of cheese. Higher levels of proteolysis were observed in IND cheeses than in TRD cheeses during ripening. Levels of residual β- and α_s-caseins were 72.2 and 48.7%, respectively, in 180-d-old TRD cheeses. However, the residual levels were 52.8% for β-casein and 18% for α_s-casein in IND cheeses. Similar differences were noted for the reversed-phase HPLC peptide profiles of 2 types of cheeses. Also, higher concentrations of peptides were eluted in IND cheeses than in TRD cheeses during ripening. A total of 73 volatile compounds, including alcohols (16), esters (17), acids (14), terpenes (7), ketones (5), aldehydes (4), and miscellaneous (10) were identified. The IND cheeses contained higher levels of carboxylic acids, esters, alcohols, and terpenes than the TRD cheeses; however, the same levels of methyl ketones were determined in the 2 types of cheeses at the end of ripening. These may be due to some differences (e.g., pasteurization and scalding temperature, among other factors) in the manufacture of the 2 types of Beaten cheeses. The textural profile of Beaten cheeses showed that TRD production method resulted in firmer, less fracturable, and stiffer cheeses than the IND production method. In conclusion, the results suggest that the use of industrial production method (pasteurization of cheese milk and curd scalding at 70°C) in the manufacture of Beaten ewe milk cheese enriched the volatile profile of the cheese.     

Changes during ripening in chemical composition,proteolysis, volatile composition and texture in Kashar cheese made using raw bovine,ovine or caprine milk

Kashar cheeses were manufactured from pure ovine (OV), bovine (BV) and caprine (CP) milk, and the chemical composition, cheese yield, proteolysis, hardness, meltability and volatile composition were studied during 90 days. Gross chemical composition, cheese yield and level of proteolysis were higher in OV cheeses than those of BV or CP cheeses. Glu, Val, Leu, Phe and Lys were the most abundant free amino acids (FAA) in the samples, and the concentrations of individual FAA were at the highest levels in OV cheeses with following BV and CP cheeses. Urea‐PAGE patterns and RP‐HPLC peptide profiles of the BV cheeses were completely different from the small ruminants’ milk cheeses (OV or CP). Higher and lower hardness and meltability values were observed in CP cheeses, respectively. OV cheeses resulted in higher levels of the major volatile compounds. In conclusion, the Kashar cheese made using OV milk can be recommended due to high meltability, proteolysis and volatiles.     

Improving the quality of Ras-type cheese made from recombined milk containing high levels of total solids

Ras type cheese was made from recombined milk (RM) containing normal (12·5%) or high levels of Total Solids (TS) (25%, 32% or 40%) using fresh or recombined cream. Cheese curds obtained from RM containing high TS levels were moulded directly or after washing with warm water (50°C) for 10 min before moulding. The cheeses were matured at 7°C or 15°C. Cheese made from fresh milk was better in flavour and consistency than any of the cheeses made from RM. Use of RM in which fresh cream was used gave cheeses of better quality than those made from RM containing recombined cream. Washing the curd made from all RMs resulted in cheeses with better flavour and body characteristics than those made from unwashed curd. Cheese made from RM containing 25% TS with or without washing of the curds was of better quality than those made from RM containing 32% or 40% TS.The changes of nitrogenous fractions, degradation of α_sI- and β-caseins, accumulation of free amino acids and the formation of free fatty acids were reduced as the level of TS in RM was increased. All cheeses made from washed RM curd showed greater proteolysis and lipolysis compared with those made from unwashed curd. Storage of RM cheese at 15°C accelerated its ripening and improved cheese quality compared with ripening at 7°C.     

Chemical Profiles of Hydrolyzed Milk Samples after Treatment with Commercial Enzymes

ABSTRACT: Commercial enzymes (protease and lipase) were used to produce highly flavored cheese-like hydrolysates from fluid milk. Free fatty acids, free amino acids, degree of proteolysis, and volatile profiles were assessed to suggest the importance of proteolytic and lipolytic activity on cheese flavor development. Free fatty acid liberation was maximized with the combined Flavourzyme™ (protease) and Palatase ® (lipase) treatment incubated at 30°C, most likely due to synergism conferred by the protease. The Flavourzyme/Palatase samples incubated at 45°C generated the highest total concentration of volatile compounds. The addition of Flavourzyme generated free amino acids and low molecular weight peptides (< 1400 MW).     

Effect of high-pressure treatment of ewe raw milk curd at 200 and 300 MPa on characteristics of Hispánico cheese

Hispánico cheese is a semihard variety made from a mixture of cow and ewe milks. Production of ewe milk declines in summer and autumn. To surmount the seasonal shortage of ewe milk and prevent the inactivation of milk enzymes by pasteurization, curd made in spring from ewe raw milk was pressurized at 200 and 300 MPa and stored frozen for 4 mo. Thawed ewe milk curds were added to fresh curd made from pasteurized cow milk for the manufacture of experimental Hispánico cheeses. Control cheese was made from a mixture of pasteurized cow and ewe milk in the same proportions as those used for experimental cheeses. Experimental cheeses exhibited lower dry matter content, higher aminopeptidase activity and total free amino acid concentration, and higher levels of acetic and propionic acids, aldehydes, alcohols, and esters compared with control cheese. In contrast, the concentration of total free fatty acids and ketones and the levels of textural parameters were significantly higher in control cheese. The use of ewe raw milk curd pressurized at 200 and 300 MPa, stored frozen and thawed for Hispánico cheese manufacture, was generally beneficial for cheese characteristics and increased cheese yield because of the lower dry matter content of experimental cheeses.     

Effect of temperature and salt on the maturation of white-salted cheese

White-salted cheeses were prepared from ultrafiltered (UF) cows' milk and salted to give final salt-in-moisture (SM) levels of 2.5, 3.2 and 4.0%. The cheeses were stored at 5°C and 10°C for up to 15 weeks. The microflora was dominated by lactic acid bacteria (LAB) but some mould growth was evident within 15 weeks at all SM levels and both temperatures. Levels of water-soluble nitrogen (WSN), attributed to chymosin activity, increased significantly with time, the rate being inversely proportional to the SM level and increasing with storage temperature. Similar effects were noted for trichloroacetic acid-soluble nitrogen (TCA-SN) and free amino acid (FAA) levels, both of which would also be affected by bacterial protease activity. The proteolytic activity was reflected by changes in the hardness and fracturability of the cheeses.     

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.     

Effects of heating milk and accelerating ripening of low fat Ras cheese on biogenic amines and free amino acids development

Two experiments were conducted to study the effects of heating milk and, consequently, incorporation of whey proteins into cheese curd, fat content, accelerating cheese ripening by attenuated lactobacilli, species of bacteria and method of attenuation on formation of biogenic amines and liberation of free amino acids. Total biogenic amines and total free amino acids increased as ripening period progressed in all cheese treatments. Total biogenic amines and total free amino acids decreased as the fat content was decreased. Heating of 3% fat milk up to 70°C caused a significant (p<0.05) increase in total biogenic amines and total free amino acid concentrations, while raising the temperature of heat treatment up to 75 and 80°C decreased them. However, heating of 2% fat milk up to 75°C caused a definite (p<0.05) increase in total biogenic arnines and total free amino acids; conversely raising heat treatment temperature to 80°C decreased them. These results indicate that there is a positive correlation between total biogenic amines and total free amino acids; moisture and salt contents affected the formation of biogenic amines, while incorporation of whey proteins had no significant effect on biogenic amines development. In a second experiment, addition of attenuated lactobacilli as adjunct bacteria caused a pronounced (p<0.05) increase in free amino acids and biogenic amines. Addition of either freeze- or heat-shocked Lactobacillus helviticus was more effective in promoting the build-up of biogenic amines and free amino acids in the resultant cheeses than in cheeses made with addition of freeze- or heat-shocked Lactobacillus casei, respectively. There was a positive correlation between free amino acids and biogenic amine contents. The type of bacteria and prolongation of ripening period significantly affected the development of biogenic amines. Tyramine was the highest biogenic amine followed by histamine, while spermidine was the lowest.     

Influence of ovine milk in mixture with bovine milk on the quality of reduced fat Muenster-type cheese

Reduced fat Muenster-type cheeses were manufactured from a mixture of bovine skim milk and ovine whole milk and from bovine milk only (control). Cheeses were evaluated at 15, 30, 60, 90, 120, and 180 d of age for numbers and type of microflora, casein hydrolysis, and amounts of free fatty acids. alpha(s1)-Casein degradation was similar for both cheeses during the aging period, but beta-casein degradation proceeded at a faster rate in the control cheese. The total amounts of free fatty acids remained constant throughout the ripening time; however, the cheeses produced with bovine/ovine milk yielded a significantly larger amount of caprylic (C8:0) and capric (C10:0) acids compared with the bovine milk cheeses. Lactobacilli increased during the aging period, while the populations of lactic acid bacteria, yeast and molds, and lipolytic organisms did not increase. Both cheeses had comparable cheese flavor intensity, but the bovine/ovine milk cheese had a greater occurrence of off flavors. The bovine/ovine milk cheeses were firmer than the bovine cheeses throughout the aging period.     

Proteolysis of Mahon cheese as affected by acoustic-assisted brining

 Mahon cheeses were brined in the presence of an ultrasonic field and ripened during 75 days at 12  °C and 85% RH. Secondary proteolysis (water-soluble N, non-protein N, and free amino acids) was measured and compared to that obtained for cheeses conventionally brined. There were no differences in water-soluble and non-protein N attributable to the brining treatment. However, cheeses acoustically brined exhibited higher concentrations of free amino acids. The release of total free amino acids was more pronounced during the first 15 days of ripening for both types of brining treatments. The changes in proteolysis (free amino acids) during cheese ripening caused by acoustic-assisted brining are indicative of a higher extent of proteolysis and may also improve cheese flavor. Received: 13 March 2000     

EFFECT OF LIPASE ENZYME ON THE RIPENING OF WHITE PICKLED CHEESE

The effect of addition of pregastric lipase enzyme on the accelerated ripening of white pickled cheese was investigated. Commercial pregastric lipase was added to milk before rennet addition at a level of 0,5, 8, 11 g per 100 L of milk and cheeses were made from this milk. Total solids, fat, total nitrogen, salt, titratable acidity, pH and free fatty acids (C₂-C_18:1) were analysed in the samples during 1–90 days of ripening period at 15 days intervals. Total solids, fat, total nitrogen, salt, titratable acidity, and pH of cheeses slightly increased during the ripening period. Free fatty acids and volatile free fatty acid contents in cheeses made from pregastric lipase added milk were affected by pregastric lipase and their contents were increased significantly (P<0.01) during the ripening period. Particularly, when cheese had a high level (11 g per 100 L milk) pregastric lipase, the amounts of butyric, caproic and caprylic acids in white pickled cheese were quite high. The relative amounts of volatile free fatty acids varied with storage time and pregastric lipase levels.     

Comparison of the volatile profiles of Arzúa-Ulloa and Tetilla cheeses manufactured from raw and pasteurized milk

Levels of volatile compounds in Arzúa-Ulloa and Tetilla cheeses manufactured from raw and pasteurized milk were investigated. Analysis of volatile compounds in six raw milk (RM) starter-free cheeses (15–45 days old) and six pasteurized milk (PM) cheeses made with deliberately added starters (15–45 days old) manufactured in different dairies, was performed on an automatic dynamic headspace apparatus coupled to a GC/MS. The volatile fraction of RM cheeses displayed 46 volatile compounds (34 for PM cheeses) including fatty acids, esters, aldehydes, alcohols, ketones, hydrocarbons and sulphur compounds. Fatty acids and several esters were only detected in RM cheeses. Moreover, the highest contents of methylketones, secondary alcohols and branched-chain aldehydes and alcohols were also observed in RM cheeses. All results confirm more intense lipolysis in RM cheeses than in PM cheeses. In addition, branched-chain aldehydes and alcohols were significantly more abundant in RM than in PM cheeses, which indicates that catabolism of branched-chain amino acids was significantly higher in RM cheeses. This study has provided useful information which will allow the selection of starter and non-starter bacteria more suitable for manufacturing Arzúa-Ulloa and Tetilla pasteurized milk cheeses with organoleptic characteristics similar to those of traditional raw milk cheeses.     

Ripening of Camembert-type cheese made from caprine milk using calf rennet or kid rennet as coagulant

Camembert-type cheese was made from caprine milk using either calf rennet or kid 'Grandine' rennet as coagulant. The pH of all cheeses increased throughout ripening and levels of pH 4.6-soluble nitrogen increased from 8.1 to 18.2% of total nitrogen (TN) and from 6.9 to 20% TN for the cheeses made using calf rennet and kid rennet, respectively. Degradation of β-casein, measured by urea–polyacrylamide gel electrophoresis, and total and free amino acids were greater in the cheese made using kid rennet. Production of peptides, analysed by high performance liquid chromatography (HPLC), was slightly more extensive in the Camembert-type cheese made using calf rennet as coagulant. In general, a higher degree of proteolysis was found in Camembert-type cheese made from caprine milk using kid rennet than in cheese made using calf rennet as coagulant.