Domiati Cheese Research Articles

Immobilization of recombinant strains of Saccharomyces cerevisiae for the hydrolysis of lactose in salted Domiati cheese whey

Intergeneric protoplast fusants SK-26 and SK-35 between Saccharomyces cerevisiae ATCC 4126 and Kluyveromyces lactis CBS 683 produced 2.70 ml dl–1 and 1.52 ml dl–1 (v/v) of ethanol during fermentation of lactose at 25 °C in salted Domiati cheese whey containing 6.1 g dl–1 (w/v) NaCl when entrapped in alginate spheres, whereas the free recombinant cells produced 2.36 ml dl–1 and 1.09 ml dl–1 (v/v) of ethanol. Yeast hybrids spheres can be used nine times with accumulated increases of ethanol production of 9.1 ml dl–1 and 8.98 ml dl–1 (v/v), respectively.

Effects of processing and storage of dairy products on lindane residues and metabolites

Residue levels of lindane and its metabolites were monitored in 25 samples of raw and sterilized milk, yoghurt, Domiati & Ras cheese collected from different regions in the Great Cairo Governorates. The concentrations of lindane followed the order: raw milk > Domiati cheese > sterilized milk > yoghurt=Ras cheese. Most samples were found to contain three or more metabolites at different levels. Heat treatments (pasteurization, boiling and sterilization) reduced lindane levels. The reduction percentages were 65.0–73.0, 75.0–85.4, and 84.4% for lindane content and 0.1–43.0, 37.3–55.4, and 76.6% for total of lindane and its metabolites on pasteurization, boiling, and sterilization, respectively. A gradual reduction of lindane ranging from 1.4–8.9% was observed during the manufacture and storage of yoghurt for three days in a refrigerator. The reduction of lindane was higher in Domiati cheese made by acid-enzyme coagulation than that made by enzyme coagulation. On the other hand, the manufacturing process of Ras cheese removed 36.7% lindane after storage (ripening) periods of 6 months. This may be due to the effect of microorganisms during storage.

Volatile compounds of Domiati cheese made from buffaloe's milk with different fat content.

Buffaloe's milk was manufactured to Domiati cheese with different fat content in the cheese milk (1%, 3.5% and 7%). Results obtained during the ripening period revealed that the low fat cheese (Karish) is not able to long period storage, while half cream cheese had a good quality and flavour along the ripening period. The full cream cheese did not exceed the first month of ripening, then it deteriorated. The main components found were acrolein (propenal), heptanal, acetone, butan-2 one, ethanol, butan-2 ol, 2-methylpropan- 1-ol, 3-methyl butan-1-ol, ethyl propionate, propyl propionate, pentane and octane. Methyl mercaptan, methyl thiopropionate, and dimethyl trisulfide together with propyl butyrate, were existed in the samples which are characterized as bad cheese samples. Most of the previous compounds were developed after 1 month of ripening period.

Malt extract for enhancing flavour development of ultrafiltered Domiati cheese

Ultrafiltered (UF) retentate was used in the manufacture of Domiati cheese, and the effectiveness of malt extract at levels of 0.025%, 0.05% or 0.075% in accelerating flavour development in UF Domiati cheese was evaluated. The results indicated that untreated UF Domiati cheese had higher moisture, fat and total N, and lower salt, acidity and proteolysis, than conventional Domiati cheese. There were no significant differences in lipolysis or bacterial counts between the conventional and untreated UF Domiati cheeses. Addition of malt extract slightly increased the moisture and acidity, but did not affect the fat, total N or salt content of the resultant cheeses. Malt extract-treated UF Domiati cheeses showed significantly higher proteolysis, lipolysis and bacterial counts compared with the other cheeses. This was more pronounced with the increase in the malt extract added to UF milk. Conventional Domiati cheese was organoleptically better than UF Domiati cheese without additives. However, incorporation of malt extract into UF Domiati cheese greatly enhanced the flavour development and improved the body and texture characteristics of the cheese. UF Domiati cheese with added malt extract (0.075%) was significantly higher in quality after 2–4 weeks of pickling than were the other cheeses.

Developments in microencapsulation science applicable to cheese research and development. A review

Abstract The applications of microcapsules for cheese technology are reviewed. Proteolytic enzymes for use in cheese ripening may be encapsulated in microcapsules to avoid premature proteolysis in cheese milk. Alginate, milk fat, and phospholipid have been used as encapsulating materials. Alginate is not a natural constituent in milk products, and, in addition, the alginate capsules are rather leaky. Milk fat capsules show good encapsulation properties. However, strong detergents, which do not have GRAS status, are needed to keep them stable. Phospholipids form membrane structures, liposomes, in contact with water. These liposomes are stable without added detergents, and the phospholipids are natural constituents of the milk fat membrane. Controlled release of enzymes in the cheese can be achieved by technologically altering the stability of the liposomes with respect to time, temperature and pH. Liposomes may be constructed with different sizes and number of lamellae, according to the preparation method. The various types of liposome (MLV, SUV, REV and DRV) are defined and described. Several enzymes have been encapsulated in liposomes. DRV liposomes have shown the highest efficiency for the encapsulation of enzymes. Various liposome-encapsulated enzymes have been used to accelerate the ripening of Cheddar, Saint Paulin, Domiati and Gouda cheese. Liposome-encapsulated enzymes have a potential for use in accelerated cheese ripening, but the price of the phospholipid must be reduced, and a good and cheap scaled-up preparation method must be developed.

Investigation of volatile flavor compounds in fresh and ripened Domiati cheeses

The volatile compounds of three fresh and six 3-months-ripened Domiati cheeses were investigated with a dynamic headspace GC-MS system. Unlike the amino acid degradation products and the diketones, acrolein, propan-1-ol, butan- 2-one, butan-2-ol, and a large number of esters appear during maturation. Moreover, various sulfur compounds contribute significantly to the overall cheese aroma, particularly when bad ripening occurs. Most of the volatile compounds are synthesized after 2 months of maturation.

Coagulation of buffaloe's milk and resultant Domiati cheese characteristics as affected by salting and replacement with sour cream butter milk

AbstractThe action of rennet on buffaloe's milk replaced by 5, 10 or 15% of sour cream butter milk salted by either 6 or 10% before renneting or after the rennet action was studied as the non protein nitrogen (NPN) content. Buffaloe's milk without replacement of butter milk was taken as a control. Results revealed that addition of salt to milk before renneting inhibited the rennet action and consequently increased the coagulation time. The inhibition increased with the increase in the salting percent. In contrast, replacement of buffaloe's milk by sour cream butter milk enhanced the rennet action and shortened the coagulation time compared with the control. This effect was increased proportionally by the increase in sour cream butter milk. Enhanced protein breakdown, slightly higher accumulation of free fatty acids and good quality were observed in Domiati cheese treated with sour cream butter milk compared with the control. This effect was pronounced in case of 15% sour cream butter milk.

Salmonellae, Salmonellosis, and Dairy Foods: A Review

Salmonellae continue to be a major concern for the dairy industry because these bacteria have caused recent outbreaks of illness and have been isolated from various dairy products in the market place. Salmonellae are generally not heat resistant and normally grow at 35 to 37°C, but they can grow at much lower temperatures, provided that the incubation time is suitably extended. To minimize problems, foods should be held at or below 2 to 5°C at all times. Both conventional and rapid methods are available to isolate salmonellae from dairy foods and to identify the bacteria. Salmonellae behave differently in different kinds of cheese: they survived in ripening Cheddar cheese for up to 7 mo at 13°C and for 10 mo at 7°C; in cold-pack cheese food for several weeks, depending on the pH and preservative used; and in Domiati cheese 13 to 36 d, depending on the manufacturing process used. When Mozzarella cheese was made, temperatures of stretching and molding (60°C) killed all salmonellae present, but, in cottage cheese, survival of the pathogen depended on the cooking temperature of curd. Spray drying of skim milk killed substantial numbers of salmonellae, but some survivors remained. Butter readily supported growth of salmonellae at room temperature, and neither freezing nor refrigeration for brief periods eliminated salmonellae from butter. Use of appropriate hygienic procedures, e.g., Hazard Analysis Critical Control Point system, during processing should reduce the likelihood of salmonellosis outbreaks associated with dairy foods.

New type of Domiati cheese of potential benefit to people with high blood cholesterol.

Part of the milk used for manufacturing Domiati cheese was replaced by buttermilk at rates of 0, 20, 30, 40, 50 and 60%. The fat and SNF contents were standardized at 5 and 10% respectively. The hypocholesterolaemic effect of buttermilk when incorporated into cheese was tested with rats by including cheese manufactured with and without buttermilk mixed in their diet at a rate of 30% for a period of 60 d. When the diet containing Domiati cheese free from buttermilk (control cheese) was given to rats, there were highly significant increases in serum and liver cholesterol. However, when part of the milk used in manufacturing Domiati cheese was replaced by buttermilk the increases in serum and liver cholesterol concentrations were reduced. These reductions were proportional to the proportion of buttermilk incorporated in the milk used to manufacture the cheese. When 50% of the milk used for Domiati cheese was replaced by buttermilk the hypercholesterolaemic effect of Domiati cheese was nullified and the serum and liver cholesterol concentrations were restored to their normal values. The effect of replacing 50% of the milk used in the manufacture of Domiati cheese by buttermilk on the quality of the cheese was tested periodically during the ripening period. The buttermilk improved the flavour of the cheese whilst only slightly affecting its ripening.

Ultrafiltration of reconstituted skim milk

The manufacture of Domiati cheese by ultrafiltration (UF) processing of recombined milk bas been described in several reports (El-Shibinyet al.1982; Bogaard, 1986). This method has several potential advantages in areas short in milk production. In Egypt, a new plant has been established recently for the manufacture of Domiati cheese on the basis of this technology.The behaviour of fresh pasteurized skim milk during UF has been described (Glover, 1971; Setti & Peri, 1976; Patel & Reuter, 1985; Chiang & Cheryan, 1986). Similar studies are lacking for reconstituted skim milk or recombined milk. Skim milk powder is usually subjected to variable heat treatments during processing which are known to affect its properties. These heat treatments have been used as a basis for classification of skim milk powders. Therefore, studies on UF of reconstituted milks previously subjected to different heat treatments would be important in the adaptation of this technology to cheese manufacture.We describe here results obtained for permeation rates of reconstituted skim milk during UF compared with fresh pasteurized skim milk.

The Influence of Sodium Chloride on the Activity of Yeast in the Production of Single Cell Protein in Whey Permeate

Whey can contain substantial amounts (6 to 10%) of sodium chloride, such as whey from the pressing of hard cheese or when from making Domiati cheese where salt is added to milk prior to renneting. Nine different lactose-fermenting yeasts were cultured in shake flasks using Cheddar cheese whey permeate as the fermentation medium. The pH and temperature of growth media were kept at 5 and 32°C, respectively. We studied the effect of 3, 6, or 9% concentrations of sodium chloride on the ability of yeasts to convert whey into biomass.Kluyveromyces marxianus var. marxianus ATCC 28244 and Candida tropicalis ATCC 20401 were more efficient in producing cell mass from 0 to 9% salt permeate than the other strains.

Composition and microstructure of Domiati cheese made from reconstituted UF milk

The quality of Domiati cheese made from reconstituted UF milk was improved, compared with that made from reconstituted milk by the conventional method. The clotting time decreased, the coagulum strength and the protein and fat retention increased, and this resulted in a firmer coagulum and smoother body. UF cheese had higher moisture, fat in DM, protein in DM, proteolysis of proteins and pH value than conventional cheese. The accumulation of free amino acids was significantly different between the control and the experimental cheeses and increased throughout the ripening period. The liberation of Free Fatty Acids showed the same trend in both cheeses except for a small increase of free Volatile Fatty Acids in UF cheese which had a good finish and appearance, better consistency and flavour than the control cheese. The microstructures of the cheeses were quite similar and the protein matrix was in a loose and porous structure. The casein network was still recognizable after four months of ripening.

Studies on thermonuclease production by Domiati cheese microflora

Summary A total of 1005 isolates from Domiati chee se representative of thermoduric bacteria (431), Gram negative bacteria (270), yeast (159), faecal streptococci (131), micrococci (72) and S. aureus (32) were examined for their capability to pro duce thermonuclease (TNase). Only nine out of 131 isolated faecal streptococci, in addition to the 32 S. aureus isolat es were TNase producers. Based on the observed differences in heat stability of TNase produced by isolated S. aureus and faecal streptococci, it could be recommended that heat treatment used with TN ase test should be prolonged up to 20 min. Results also indicated that increasing salt content of milk beyond 10 % and up to 20 % obviously affected TNase production by S. aureus strains. TNase test, therefore, might not be used as an index for likely presence of S. aureus in case of Domiati cheese made from salted milk with more than 10 % sodium chloride.

Free fatty acids and quality of Domiati cheese made from dried milks as affected by added lipase

Domiati cheese was made from skimmed or whole dried milk with and without an added lipase preparation (Italase). Dried milk cheeses differed from fresh milk cheese in showing less flavour intensity and lower levels of free fatty acids with chain lengths of C 2 to C 18 . Treatment of reconstituted milk with Italase, at a level of 0·02%, enhanced the formation of free fatty acids and this was associated with an improvement in cheese flavour. Thus the levels of free fatty acids and flavour intensities of dried milk cheeses with added lipase approached or even exceeded those of fresh milk cheese of the same pickling period.

Microstructure and chemical changes in domiati cheese made from ultrafiltered milk

Cheese of good quality was made from ultrafiltered cow's milk and compared with that made by a conventional method. Domiati cheese made by ultrafiltration had a uniform and closed texture, good appearance and better organoleptic properties, and the breakdown of protein, the accumulation of free amino acids and the liberation of Volatile Free Fatty Acids were faster than in cheese made by the conventional method. The pattern of total amino acids was nearly the same and slightly decreased during ripening; glutamic acid, aspartic acid, leucine and lysine represented about half of the total amino acid concentration in both cheeses. The microstructure of the protein matrix in Domiati cheese consists of fused casein micelles in homogeneous masses. There were similarities in the appearance of the cheese matrix between the cheese made by the conventional method and that made from ultrafiltered milk when young and during ripening.

A study on the ripening of white pickled Brinza cheese made from ewe's milk

AbstractThe chemical composition, the microbiological feature and the microstructure of young and mature Brinza cheese were investigated. During ripening fat, total nitrogen, soluble nitrogen, non protein nitrogen; peptide nitrogen, amino acid nitrogen and acidity increased while the microbial feature decreased.The amount of free amino acids and free fatty acids increased with storage and the patterns of their distribution changed with the highest levels for lysine, glutamic, oleic, palmatic and myristic acids.The microstructure of fresh Brinza cheese consists of casein micelles joined together to form an open network with clustering of micelles. During ripening, these micelles continued to aggregate and coalesce with increasing fusion process to give more homogeneous and loose structure similar to that in white pickled Domiati cheese.

Microstructure, free amino acids and free fatty acids in Domiati cheese treated with β‐galactosidase

AbstractDomiati cheese was made from partially lactose hydrolyzed fresh milk and examined for the microstructure, the free amino acids, and the free fatty acids when young and after two months.The addition of β‐galactosidase to cheese milk before renneting enhanced the fusion of protein and the formation of more homogenious structure of submicelles compared to control, as well as produced a good quality cheese of 1.5–2.5 fold free amino acids and free fatty acids as much as those of control. The differences were particularly great in respect of serine, phenylalanine, aspartic acid, glutamic acid, myristic acid, palmatic acid and oleic acid.

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%).

Growth and Survival of Staphylococcus aureus in Egyptian Domiati Cheese

Domiati cheese was prepared from unsalted raw milk and from raw milk with 5 or 10% added sodium chloride, Milks were inoculated with enterotoxigenic Staphylococcus aureus strain 100 (produces enterotoxin A) before addition of salt and rennet. Cheeses were stored in whey containing 15% sodium chloride; were held at 30°C and were examined periodically for S. aureus count, aerobic plate count, DNase and moisture and salt contents. Numbers of S. aureus increased rapidly during preparation of cheese. There was a rapid decrease in number of viable S. aureus during storage of cheese made from unsalted milk and cheese made from milk with 5% added salt. In cheese from milk with 10% added salt, S. aureus survived until the fourth week. An increase in salt content and a decrease in the pH value of all cheeses occurred during storage in salted whey. DNase was detected only in cheese made from salted milk, but these samples did not contain a detectable amount of staphylococcal enterotoxin either after cheeses were made or after they were stored for 1 week.

Domiati cheese made with ultrafiltered reconstituted milk and lipolysed recombined cream

SummaryA new method was developed for making Domiati cheese, based on blending ultrafiltered reconstituted milk and lipolysed recombined cream. The chemical composition of the new product was similar to the traditional cheese. The flavour intensity increased with the amount of lipase used in the cream hydrolysis. During storage the acidity and tyrosine content of cheese from different treatments increased at nearly similar rates. The level of total volatile fatty acids was affected by the level of lipase used. Organoleptic scoring showed that cheese made with cream treated with the intermediate levels of lipase (2 or 5 g/500 g cream) ranked the highest, after 1 and 4 months of storage respectively.