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.

     

Quality of plain yoghurt made from refrigerated and CO2-treated milk

The suitability of milk preserved by refrigeration and CO₂ addition for the manufacture of plain yoghurt was evaluated using two commercial strains of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus. Yoghurts manufactured, after milk pasteurisation, from refrigerated CO₂-treated samples (pH 6.15) were compared with two different controls made from pasteurised milk, either fresh or refrigerated. The multiplication and acidification capacity of the starter as well as the evolution of organic acids were not affected by the previous refrigeration and CO₂-treatment of raw milk nor by the residual CO₂ present in pasteurised milk. However, refrigeration enhanced the production of ethanol and diacetyl. No differences on sensory properties were detected through the cold storage between yoghurts made from CO₂-treated milk and those made from refrigerated control milk. It was concluded that refrigerated milk acidified with CO₂ could be satisfactorily used in the manufacture of yoghurt.     

Manufacture of Cheddar cheese from high-pressure-treated whole milk

The cheese-making characteristics of high-pressure (HP)-treated milk were examined. The rennet coagulation time of pasteurised milk decreased after HP treatment at 400 MPa but increased after treatment at 600 MPa. The L-value (whiteness) of milk decreased directly after HP treatment but, over the course of coagulation, whiteness of HP-treated milk increased to the same level as in the control. Cheddar cheese was then manufactured from raw whole milk or whole milk treated by high-pressure (HP) at 400 MPa (HP400) or 600 MPa (HP600) for 10 min at 20 °C. HP treatment of raw milk at 600 MPa resulted in a 3.66 log reduction in the initial counts of non-starter lactic acid bacteria (NSLAB), decreased protein and fat content, as well as a lower pH compared to the control. Furthermore, higher treatment pressures resulted in increased incorporation of β-lactoglobulin into the cheese curd, with parallel increases in yield by 1.23% and 7.78% for HP400 and HP600 cheeses, respectively. Overall, this study showed that the effects of HP treatment on milk proteins increased rennet coagulation times and changes in cheese composition at day 1.Industrial relevanceHigh-pressure treatment is a novel technology which has been applied to a number of commercial food products. In this study, HP-induced changes in milk proteins resulted in increased cheese yields and increased cheese whiteness. In addition, HP treatment significantly reduced the microflora of raw milk cheese. Those attributes could be of interest for both industry and consumer.     

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.     

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%).     

Manufacture of heat and acid coagulated cheese from ultrafiltered milk retentates

Ultrafiltration technology was used for the production of direct acidified cheese. Process parameters were optimized for cheese manufacture from whole milk retentates at 4:1 volume concentration ratio. Sensory evaluation indicated that cheese from ultrafiltration was preferred equally to traditional manufacture when the cheese was of similar composition, while citric acid was the preferred acidulent. An increase in cheese yield of 3.3% and an increase in yield on dry matter mass basis of 14.7% was achieved by use of ultrafiltration. Yield efficiencies based on protein, fat or total solids increased with retentate concentration.     

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'.     

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.     

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.     

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.     

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.     

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.     

Manufacture of fresh soft white cheese (Domiati-type) from ultrafiltered goats' milk

Manufacturing procedures and compositional characteristics were studied for fresh soft white cheese (Domiati-type) made from goats' milk, using ultrafiltration (UF) and conventional processes. Yields, recovery of protein, fat, total solids and sensory characteristics of this type of cheese were also evaluated. The cheeses made by UF process was higher in pH, moisture content and ash, whereas protein and fat contents were lower compared to those cheeses made by the conventional process. An increase of 21% in cheese yields, 21–26% in protein recovery, 15–19% in fat recovery and 17–22% in total solids recovery was achieved by the UF process. Moreover, the UF process showed 83–85, 83.3, 75, 82.5 and 75% reduction in the total process time, salt, starter culture, rennet and calcium chloride used, respectively. The mean score for texture of cheeses made by UF was significantly higher than that of cheeses made by the traditional process. However, a difference in flavour and overall acceptability between UF cheeses and traditional process cheeses was not verified. The most acceptable cheeses were these made with yogurt or lactic ferment starter culture.     

Isolation of lactic acid bacteria from Lighvan cheese, a semihard cheese made from raw sheep milk in Iran

The lactic acid bacteria contributing to Lighvan cheese ripening during the different stages of production were investigated. Isolated strains from different culture media were identified phenotypically to species and subspecies level. In total, 413 strains were isolated from raw milk, 1-day-old cheese and fully ripened cheese. The most abundant species belonged to Enterococcus faecium (87 isolates), Lactococcus lactis ssp. lactis (68 isolates), Enterococcus faecalis (55 isolates) and Lactobacillus plantarum (48 isolates). E. faecium, Lc. lactis and Lb. plantarum were the predominantly isolated strains from ripened cheese. Therefore, they may contribute considerably to the aroma and flavour development of Lighvan cheese.     

Heat resistance of Lactobacillus paracasei isolated from semi-hard cheese made of pasteurised milk

Nine strains of non-starter Lactobacillus paracasei isolated from semi-hard cheese made of pasteurised milk were selected for their anticlostridial activity. Resistance to thermisation (60 °C, 5 min) and pasteurisation (73 °C, 15 s) was investigated using a submerged-coil apparatus. MRS broth-grown cultures of all nine strains survived thermisation in buffer. The level of resistance to thermisation was strain dependent and lower for freshly grown cells (stationary phase cells) than for resting cells (freshly grown cells kept diluted 10-fold in MRS broth at 17 °C for 6 days). None of the nine Lb. paracasei strains survived or recovered after pasteurisation in buffer when grown in MRS broth, while seven of the nine strains survived pasteurisation in UHT whole milk when grown in milk. Identity of the strains was successfully confirmed during the experiments using repetitive-PCR analysis. The potential of Lb. paracasei strains to survive pasteurisation of cheese milk was demonstrated.     

Manufacture of a feta cheese using skim milk retentate powder

Feta cheese was manufactured by addition of skim milk retentate powder to the cheese milk. In comparison with the reference cheese 40% of the initial milk was substituted on protein base by the powder. This substitution had little or no effect on proteolysis, lipolysis and the rheological properties of the cheese. Also sensory evaluation demonstrated that the experimental cheese was of the same quality as the reference cheese. Protein substitution proved to have some important advantages, such as a better yield and more economical cheese production. Furthermore, the skim milk retentate powder seems to have fat replacing properties.     

The influence of milk powder characteristics on the properties of halloumi cheese made from recombined milk*

The properties of halloumi made from recombined milks that had been prepared using milk powders processed by different methods were investigated. With skim milk powder, decreases in heat treatment of the liquid skim before drying were found to improve the stretch and melt properties of the cheese. In contrast, the level of solids in the skim concentrate before drying had no effect on the cheese characteristics. Ultrafiltration was also used to concentrate milk for spray drying. The resultant powder was recombined to give protein levels equivalent to that of normal milk and to that of milk concentrated fivefold. In both cases the recombined milks could be converted into high quality halloumi.     

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.     

Manufacture of processed cheese from Iraqi white soft cheese

Processed cheese was made from different samples of Iraqi white soft cheese by adding 3.5% emulsifying salts and 15–25% water depending on the chosen type of processed cheese. Arabic gum was used to firm the cheese at a rate of 0.08%. Total solids ranged from 46.8–43.4% in the firm and spread types, respectively. Laboratory processed cheese gave excellent quality compared with local processed cheese.