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.     

Transfer of protein from milk to cheese

This report concerns measurement of paracasein in milk and transfer of protein from milk to cheese. In the main experiment, two vats of Cheddar cheese were made from each of 11 lots of milk from one large herd over a period of 7 mo. Exclusion of solutes from moisture in paracasein micelles in milk and cheese was central to estimation of paracasein and to the transfer of protein from milk to cheese and whey. Solute-exclusion by paracasein and its changes during cheesemaking could be visualized by considering paracasein micelles to be a very fine sponge. The sponge excludes solutes, especially the large solutes like whey proteins. The sponge shrinks during cheesemaking and expels solute-free liquid, thereby slightly diluting the whey surrounding the micelles inside the curd. Paracasein N in milk was calculated as the difference between total milk N and rennet whey N, the latter adjusted to its level in milk. Adjustment used appropriate solute-exclusion factors (h) of the protein fractions of whey and 1.08 for paracasein and associated salts. They were combined to give a factor Fpc, which adjusted the level of rennet whey N to its level in milk: 1.001 x (1 - 1.01 x FM/100 - Fpc x pc/100), where FM = fat in milk, pc = estimated paracasein, and 1.001 = dilution of milk by chymosin and CaCl2. The mean Fpc was 3.03. Differences in values were small among different procedures for calculating paracasein, but they are considered to be important because they represent biases, which, in turn, are important in analyses commercially. We conclude that solute exclusion by moisture in paracasein must have decreased during cheesemaking because the ratio of moisture to paracasein in the final cheese was 1.5, much less than the h of 2.6 for serum proteins by paracasein. Release of solute-excluding moisture from paracasein during cooking was likely the reason for lower total N in cheese whey than in the rennet whey in the paracasein analysis. Paracasein, estimated to be in cheese, curd fines, salted whey, and whey during cheddaring, was 98.21, 0.20, 0.25 and 0.19%, respectively, of the paracasein in milk for a total of 98.85% (SD of 22 vats = 0.46); the location of the missing paracasein is not known. On the other hand, recovery of milk N in cheese and wheys was 99.92% (SD = 0.37%). Nitrogen in paracasein and its hydrolysis products in cheese was estimated to be 98.51% of total cheese N. Proteose-peptone from milk appeared not to be included with the paracasein in appreciable amounts. Some was apparently included with denatured serum proteins during Rowland fractionation of whey, perhaps as a coprecipitate. Measured paracasein would include fat globule membrane proteins in milk containing fat, and denatured whey proteins in heated milks. It was concluded that the method of measurement and the associated calculations are integral parts of the definition and quantification of paracasein in milk.     

Slower proteolysis in Cheddar cheese made from high-protein cheese milk is due to an elevated whey protein content

A growing number of companies within the cheese-making industry are now using high-protein (e.g., 4–5%) milks to increase cheese yield. Previous studies have suggested that cheeses made from high-protein (both casein and whey protein; WP) milks may ripen more slowly; one suggested explanation is inhibition of residual rennet activity due to elevated WP levels. We explored the use of microfiltration (MF) to concentrate milk for cheese-making, as that would allow us to concentrate the casein while varying the WP content. Our objective was to determine if reducing the level of WP in concentrated cheese milk had any impact on cheese characteristics, including ripening, texture, and nutritional profile. Three types of 5% casein standardized and pasteurized cheese milks were prepared that had various casein:true protein (CN:TP) ratios: (a) control with CN:TP 83:100, (b) 35% WP reduced, 89:100 CN:TP, and (c) 70% WP reduced, 95:100 CN:TP. Standardized milks were preacidified to pH 6.2 with dilute lactic acid during cheese-making. Composition, proteolysis, textural, rheological, and sensory properties of cheeses were monitored over a 9-mo ripening period. The lactose, total solids, total protein, and WP contents in the 5% casein concentrated milks were reduced with increasing levels of WP removal. All milks had similar casein and total calcium levels. Cheeses had similar compositions, but, as expected, lower WP levels were observed in the cheeses where WP depletion by MF was performed on the cheese milks. Cheese yield and nitrogen recoveries were highest in cheese made with the 95:100 CN:TP milk. These enhanced recoveries were due to the higher fraction of nitrogen being casein-based solids. Microfiltration depletion of WP did not affect pH, sensory attributes, or insoluble calcium content of cheese. Proteolysis (the amount of pH 4.6 soluble nitrogen) was lower in control cheeses compared with WP-reduced cheeses. During ripening, the hardness values and the temperature of the crossover point, an indicator of the melting point of the cheese, were higher in the control cheese. It was thus likely that the higher residual WP content in the control cheese inhibited proteolysis during ripening, and the lower breakdown rate resulted in its higher hardness and melting point. There were no major differences in the concentrations of key nutrients with this WP depletion method. Cheese milk concentration by MF provides the benefit of more typical ripening rates.     

Manufacture of cheese made from CO2-treated milk

Cheeses were manufactured from pasteurised milk (control), pasteurised milk acidified to pH 6.0 with CO₂, and milk acidified to pH 6.0 with CO₂ prior to pasteurisation. Production of cheese from CO₂-treated milk at pH 6.0 reduced the amount of rennet necessary for coagulation by about 75%. Although acidification reduces the amount of lactic acid produced by starter during incubation of milk, no significant differences in lactic acid content were detected between cheeses manufactured from non-acidified or CO₂-acidified milks. Cheeses produced from CO₂-treated milk showed less proteolysis than control cheeses, but no significant differences in sensory characteristics between cheeses were detected.     

Ripening changes of Kashkaval cheese made from cow's milk

Kashkaval cheese was made from cow's milk and examined for the changes in its microstructure and chemical composition during ripening.The percentages of fat, protein, soluble nitrogen, non-protein nitrogen, amino acid nitrogen and the total free fatty and amino acids increased during ripening.The presence of glutamic acid, leucine, phenylalanine, valine and tyrosine at high concentration, and of butyric, caproic, caprylic and capric acids may contribute to the formation of Kashkaval cheese flavour. The small concentrations of acetic and propionic acids preclude any contribution to Kashkaval flavour.In young cheese, casein aggregates lose their spherical shape due to the scalding and kneading processes and they form a fibrous network including cavities.During ripening, dissociation and fusion processes occur in protein fibres to form a more homogeneous structure and interaction between layers of casein sheets increases to give a more compact structure.     

Composition of cheddar cheese made with different milk clotting enzymes.

Six commercial milk clotting preparations from animal and fungal sources were used to make cheddar cheese. The cheeses were analyzed initially and over 6-mo ripening for proximate composition, minerals, amino acids, soluble protein, nonprotein nitrogen, free fatty acids, lactones, and flavor development. No significant differences in the composition of the cheeses could be attributed to the type of clotting enzyme. One lot of one enzyme showed increased lipolytic activity which indicated contamination and suggested that the purity of the enzyme preparation should be checked.     

Microstructure and chemical changes in Twarog cheese made from ultrafiltrated milk and from lactose-hydrolysed milk

Twarog cheese was manufactured from fresh milk, lactose-hydrolysed milk and retentate. Microstructure, chemical composition, protein breakdown, amino acid distribution and organoleptic properties were studied during ripening.Inoculation of the milk with β-galactosidase, before cheese processing, reduced the clotting time, enhanced the protein breakdown and enhanced amino acid accumulation during ripening. Concentrating the milk, by ultrafiltration, prolonged the coagulation time and resulted in a cheese with greater amounts of moisture, fat, total nitrogen and higher pH than other cheeses.Essential free amino acids are considered to constitute more than half of the total free amino acids of Twarog cheese and glutamic acid, leucine and phenylalanine are the major free amino acids in the ripened cheese.Quality of the cheese was improved either by ultrafiltration or by lactose hydrolysis and the acceptable flavour was more pronounced in β-galactosidase-treated cheese.Microstructure of the protein in young cheeses does not differ in all treatments. The disintegration and fusion of casein advanced during ripening in the outer protein matrix more than internally. The appearance of the cheese matrix was similar in both control and ultrafiltrated cheeses while the casein in β-galactosidase-treated cheese fused faster than in other treatments.     

Improving the quality of Domiati cheese made from recombined milk

A trial has been carried out to improve the quality of Domiati cheese made from recombined milk. Addition of whey proteins/CMC complex recovered from whey, corresponding to 25% to 75% of cheese milk weight, increased cheese yield, reduced loss of weight during pickling and enhanced the body of cheese. Flavour intensity and the formation of soluble nitrogen compounds and Volatile Fatty Acids (VFA) were not affected.Incorporating Piccantase B or Kapalase K (commercial lipases) at 0·025% and 0·05% levels into the same cheese milk improved flavour intensity and the production of VFA. Flavour intensity of 4-weeks-old cheese made from lipase-treated milk (0·05%) was more pronounced than that of 8-weeks-old control cheese. Piccantase B was more effective in this respect. After 8 weeks of pickling, a rancid flavour was developed in cheese made from milk treated with the higher concentration of lipases (0·05%).     

Production and properties of a semi-hard cheese made from soya milk

Summary A semi-hard soya cheese, with mean moisture content 61.5%, crude protein 21.8% and fat 2.6%, was produced from reconstituted soya-milk powder using a starter culture of Streptococcus thermophilus and Lactobacillus fermentum . The physical properties of the cheese, as determined with a Texture Profile Analyser , were similar to a cheese made to the same compositional standards from bovine milk. A taste panel of Far Eastern subjects did not find the flavour of the fresh soya cheese acceptable but, when cubes of the cheese (1 cm³) were deep-fried in corn oil, the hedonic rating improved significantly. It is suggested that the cheese could be used as a protein-rich component of a meal, e.g. to replace meat in a stew, or as a 'snack food'.     

Potential aflatoxin hazards to human health from direct mold growth on Teleme cheese

Ninety-four commercial Teleme cheese samples were examined for aflatoxins produced by direct mold growth. The mycoflora on the cheese and in the atmosphere of Teleme cheese plants also were monitored. Penicillium and Aspergillus genera were tested for aflatoxin production after growth on Teleme cheese at 25 degrees C. In all cases, over 78% of the molds were Penicillium species. Aspergillus made up 3.8 to 3.9% and 0 to 7.3% of the mold on cheese and in the plant atmosphere, respectively. None of the commercial samples contained aflatoxins and none of the 448 Penicillium isolates was an aflatoxin producer. Of 22 Aspergillus species, one was capable of producing aflatoxins after direct growth on cheese. Because the physicochemical characteristics of Teleme cheese (high moisture, low pH, and medium salt concentration) favor mold growth, care should be taken to avoid contamination of the cheese by aspergilli.     

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.     

Manufacture of cheese made from CO2-treated milk

Cheeses were manufactured from pasteurised milk (control), pasteurised milk acidified to pH 6.0 with CO₂, and milk acidified to pH 6.0 with CO₂ prior to pasteurisation. Production of cheese from CO₂-treated milk at pH 6.0 reduced the amount of rennet necessary for coagulation by about 75%. Although acidification reduces the amount of lactic acid produced by starter during incubation of milk, no significant differences in lactic acid content were detected between cheeses manufactured from non-acidified or CO₂-acidified milks. Cheeses produced from CO₂-treated milk showed less proteolysis than control cheeses, but no significant differences in sensory characteristics between cheeses were detected.

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Herstellung von Käse aus CO₂-behandelter Milch

Zusammenfassung Käse wurde in drei verschiedenen Varianten hergestellt: aus pasteurisierter Milch (Kontrollkäse) sowie aus mit CO₂ auf pH 6.0 angesäuerter Milch, die nach der Säuerung pasteurisiert wurde bzw. angesäuerter Milch, die im voraus pasteurisiert worden war. Es wurde beobachtet, daß die für die Koagulation erforderliche Labmenge bei der Herstellung von Käse aus durch CO₂ auf pH 6.0 angesäuerter Milch, im Vergleich mit Kontrollkäse, auf 75% abnimmt. Der Gehalt der Milch an Starter-Kulturen nahm durch die CO₂-Behandlung ab. Allerdings konnten keine signifikanten Unterschiede im Milchsäuregehalt zwischen den aus nicht angesäuerter bzw. angesäuerter Milch hergestellten Käsen festgestellt werden. Aus CO₂-behandelter Milch hergestellter Käse zeigte geringere Proteolyse als der Kontrollkäse, jedoch konnten keine signifikanten sensorischen Unterschiede zwischen den untersuchten Varianten festgestellt werden.

     

Primary proteolysis studied in a cast cheese made from microfiltered milk

Primary proteolysis was studied in a starter-free cheese model made from microfiltered (MF) milk (19.0% casein,<0.2% whey proteins). Specificity of plasmin and chymosin activity was investigated in the pH range 5.0–6.0, by analysis of peptide composition using high-performance liquid chromatography and liquid chromatography–mass spectrometry. Hydrolysis experiments with purified caseins were performed to aid identification of peptides released by specific activities. Plasmin had no activity in cheese below pH 5.4, while its activity increased from pH 5.4 to 6.0. Chymosin activity on the Phe₂₃–Phe₂₄ bond of α_S1-casein had an optimum pH around 5.3, while release of the bitter peptide β-casein (f193–209), effected by chymosin, was highest at pH 6.0. At pH <5.3, the specificity of chymosin on α_S1-casein changed, and the peptide bond Leu₂₀–Leu₂₁ was cleaved at an increasing rate with decreasing pH. Demineralisation of the MF retentate generally increased proteolytic activity.     

Elimination of the development of bitter flavour in Cheddar cheese made from milk containing heat-denatured whey protein

A method has been developed for increasing the yield of Cheddar cheese by as much as 7.5% by the incorporation of denatured whey protein in curd. The process effectively eliminates the development of intense bitter off-flavours which are generally associated with the production of cheese from acidified milk. Although the manufacturing procedure produces cheese with acceptable Cheddar flavour, the development of high quality Cheddar flavour is impaired     

Chemical changes during the ripening of Domiati cheese made from dried milk

The ripening of Domiati cheese made from fresh and dried milk was investigated. Nitrogen fractions were determined, the proteinaceous fraction of cheese was analysed on Sephadex G-100 and the free fatty acids were determined by gas-liquid chromatography. The nitrogen fractions from fresh milk cheese had higher nitrogen concentrations than those from cheese made from dried milk. The elution pattern of the proteinaceous fractions and the pattern of free fatty acids of fresh and dried milk cheese were similar. However, the small molecular weight N fractions and the concentration of free fatty acids were higher in the former cheese than the latter.     

Texture and flavour development in Ras cheese made from raw and pasteurised milk

Texture, proteolysis and flavour development in Ras cheeses made from raw or pasteurised milk with two different thermophilic lactic cultures were monitored during ripening. Results showed that at day 1 of manufacture, the moisture content and pH were lower in raw milk cheese than in pasteurised milk cheeses. Levels of water-soluble nitrogen, casein breakdown, free amino groups and free fatty acids were higher in cheese made from raw milk than in that made from pasteurised milk. Textural characteristics, such as hardness, cohesiveness and chewines, increased in all treatments during the first 60 days of ripening due to the reduction in the moisture level during the second stage of salting (dry salting during the first 60 days of ripening). Cheese made from raw milk received the highest texture and flavour scores by panellists.     

Microbial and sensory changes throughout the ripening of Prato cheese made from milk with different levels of somatic cells

The objective of this research was to evaluate the effects of 2 levels of raw milk somatic cell count (SCC) on the composition of Prato cheese and on the microbiological and sensory changes of Prato cheese throughout ripening. Two groups of dairy cows were selected to obtain low-SCC (<200,000 cells/mL) and high-SCC (>700,000 cells/mL) milks, which were used to manufacture 2 vats of cheese. The pasteurized milk was evaluated according to the pH, total solids, fat, total protein, lactose, standard plate count, coliforms at 45°C, and Salmonella spp. The cheese composition was evaluated 2 d after manufacture. Lactic acid bacteria, psychrotrophic bacteria, and yeast and mold counts were carried out after 3, 9, 16, 32, and 51 d of storage. Salmonella spp., Listeria monocytogenes, and coagulase-positive Staphylococcus counts were carried out after 3, 32, and 51 d of storage. A 2 × 5 factorial design with 4 replications was performed. Sensory evaluation of the cheeses from low- and high-SCC milks was carried out for overall acceptance by using a 9-point hedonic scale after 8, 22, 35, 50, and 63 d of storage. The somatic cell levels used did not affect the total protein and salt:moisture contents of the cheeses. The pH and moisture content were higher and the clotting time was longer for cheeses from high-SCC milk. Both cheeses presented the absence of Salmonella spp. and L. monocytogenes, and the coagulase-positive Staphylococcus count was below 1 × 10² cfu/g throughout the storage time. The lactic acid bacteria count decreased significantly during the storage time for the cheeses from both low- and high-SCC milks, but at a faster rate for the cheese from high-SCC milk. Cheeses from high-SCC milk presented lower psychrotrophic bacteria counts and higher yeast and mold counts than cheeses from low-SCC milk. Cheeses from low-SCC milk showed better overall acceptance by the consumers. The lower overall acceptance of the cheeses from high-SCC milk may be associated with texture and flavor defects, probably caused by the higher proteolysis of these cheeses.     

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.     

Preparation and evaluation of pizza cheese made from blend of vetch–bovine milk

The objective of the study was to develop vetch–bovine milk (VBM) pizza cheese low in animal fat and its acceptability was determined through physico‐chemical, functional and sensory evaluations. Vetch (Lathyrus sativus) was detoxified by steeping in double its quantity of water for 8 h at 70 °C, changing the water seven times, draining and sun drying. Dried vetch was then treated with water at pH 4.0 at 90 °C for 60 min to deplete the beany flavour, then dried and milled into fine flour with Quadrumate Senior mill. The seed coat was separated as one of the mill fractions. Four types of VBM blends were prepared from vetch flour and bovine skimmed milk powder and were used to prepare cheese using 2.5% lactic acid bacterial culture of Streptococcus thermophillus and Streptococcus bulgaricus and rennet (0.15 mL L^?1, 1:40 ratio with water). The cheese was stored at 4 °C for 14 days and used as topping over the pizza shell. Physico‐chemical analyses, such as moisture, total solids, lactose, ash, fat, titratable acidity and pH, and sensory evaluations of both cheese and pizza were carried out at 0‐, 7‐ and 14‐day intervals. The stretchability and meltability of cheese increased significantly (P < 0.05) during storage. Commercial Mozzarella cheese was taken as a control. The results of this study suggested that VBM blend at the ratio of 12.5:87.5 (vetch flour:bovine milk powder) could be utilised to prepare a cheese of desirable characteristics for pizza topping.