Ras Cheese Research Articles

Application of Salt Whey from Egyptian Ras Cheese in Processed Cheese Making

The objective of this study was to evaluate characteristics of processed cheese made from salt Ras cheese whey and young Cheddar containing exopolysaccharide producing cultures (EPS) as compared with those in cheese made from EPS-negative cheeses. Processed cheeses were manufactured using young (1 day) or 1-month-old EPS-positive or EPSnegative Cheddar cheese and replacing the added water by Ras cheese whey or ultrafiltrated (UF) whey. Moisture and fat of processed cheese were standardized to 54% and 23%, respectively. Exopolysaccharide-positive processed cheese was softer, less chewy and gummy than the EPS-negative cheeses. The hardness and chewiness were lower in processed cheeses made from 1-month-old Cheddar than in the corresponding cheeses made from 1-day-old Cheddar cheese. Sensory scores for texture of EPS positive processed cheeses were higher than those of the EPS-negative cheeses. Generally, processed cheese made from replacing all added water with whey received higher scores in flavor and overall than did the corresponding cheeses made without whey. The obtained results are showing promise for application of salt whey in processed cheese making.

Effect of pasteurization and season on milk composition and ripening of Ras cheese

The objective of this study was to compare between the raw and pasteurized Ras cheese from cow's milk through the season. The chemical composition of cheese was also demonstrated as the ripening period progressed. High solids in winter milk and low solids in summer milk were observed and were attributed to the hot weather and the poorer quality pastures. Casein as a percentage of true protein and the casein to fat ratio were higher in spring and summer milk. Fat in the cheese made from winter milk was higher and the total protein was lower than that in spring and summer cheeses. The chemical changes during ripening period of six months were examined for composition, flavour intensity, acidity, pH, soluble protein and total volatile fatty acids. Raw or pasteurized cheese in each period of winter, spring and summer were evaluated for flavour, body and texture and appearance at the end of ripening. Fat and protein recovery in the cheese were not affected by season. Cheese yield from winter milk was higher than from spring and summer milk and was a result of the higher casein and fat in the milk. Raw milk cheese in winter and spring scored higher values for flavour compared to summer cheese. There was a close relationship between the good flavour and the high total volatile fatty acid. Milder flavour was associated with moderate soluble protein and low volatile fatty acid. On the other hand, pasteurized milk cheese in winter, spring and summer with adding yoghurt starter had a more compact body and smoother texture and more holes and cracks. In general, Ras cheese made from pasteurized milk achieved higher score in body and texture and lower score in flavour in comparison to Ras cheese made from raw milk through the season. Key words: Cow's milk, Ras cheese, chemical composition.

MAKING OF LOW FAT RAS CHEESE USING FAT REPLACER

MAKING OF LOW FAT RAS CHEESE USING FAT REPLACER

ISOLATION OF EXOPOLYSACCHARIDE – PRODUCING LACTIC ACID BACTERIA FROM TRADITIONAL EGYPTIAN DAIRY PRODUCTS

The present study aimed to isolate and characterize strains of exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) from traditional Egyptian dairy products. A total of 388 suspected LAB isolates were recovered from 100 samples of traditional Egyptian dairy products including Kariesh cheese, Zabady, Laban Rayeb and Ras cheese. Out of these suspected LAB cultures, 123 and 27 isolates were identified as potential LAB cocci and lactobacilli, respectively. These 150 LAB isolates were further examined for their ability to produce exopolysaccharides (EPS) in milk. Only 7LAB isolates were found to produce EPS. These isolates were cultured form Laban Rayeb (3 isolates) and Zabady (4 isolates). A PCR identification procedure was carried out to identify these EPS-producing isolates to the species level. All the 7 isolates were found to belong to Streptococcus thermophilus. These results generally suggest the possibility of using Egyptian dairy products as a source of EPS-producing LAB.

Impact of feeding systems of dairy cows on characteristics of ras cheese

Impact of feeding systems of dairy cows on characteristics of ras cheese

Protein substitution to produce a processed cheese with high branched-chain amino acids of medical and genetic importance

Background The most important metabolic impairment in patients with advanced liver disease is characterized by low levels of circulating branched chain amino acids (BCAAs). The etiology of such abnormal amino acid metabolism is multifactorial including protein restricted diet or inadequate nutritional intake as in protein energy malnutrition. Multiple studies report the beneficial effects of BCAAs supplementation to improve plasma amino acids imbalance, several neurologic diseases, protein energy malnutrition, and subsequently the survival rate of cirrhotic patients. Methods In the present study we used a protein substitution technique to synthesize a new processed cheese as a dairy source rich in BCAAs, with low phenylalanine content manufactured from Ras cheese, kariesh cheese, butter oil and phenylalanine-free milk. Chemical composition, amino acids analysis, rheological properties and sensory evaluation were done to all of the cheese samples. l-Phenylalanine was selected to induce hepatic and brain affections in Begg Albino strain c (BALB/c) mice model. Effect of 2.5%, 5% and 10% protein-replacement cheese formulas was evaluated among mice groups including histopathological sections of the liver and brain; colorimetric determination for liver enzymes; serum total and differential cholesterol profile, serum albumin, globulin and total protein along with phenylalanine levels determinations. Results Analysis of the processed cheese sample with 10% protein substitution revealed that the protein content was 7.42 mg/g (about 50% of the content in the standard processed cheese) while fat content, acidity and moisture were nearly the same. The sensory score for all the formulas ranged from 79–88. Highest content of BCAAs along with least phenylalanine content was attained in the processed cheese with 10% protein substitution. Weight of mice fed on different substitution formulas ranged from 22.8 ± 2.2–24.66 ± 2.5 g compared with 17.8 ± 1.9 g in the untreated diseased mice ( P < 0.05). Serum phenylalanine was 1.822 ± 0.42 mg/dl in the mice fed on 10% protein substitution formula compared to 6.2 ± 1.32 mg/dl in the untreated mice ( P < 0.01). There was a highly significant difference ( P < 0.01) between untreated mice and mice fed on 10% substitution cheese formula as regards the serum protein, Aspartate Transaminase (AST) and Alanine Transaminase (ALT). The improvement in histopathological findings was more apparent in the mice fed on 10% formula cheese. Conclusion The manufactured processed cheese with 10% protein substitution was proved to have a more nutritional therapeutic potential that can help in the implementation of dietary management in many medical and genetic disorders with liver and brain affections.

Preparation and properties of probiotic cheese high in conjugated linoleic acid content

The development of probiotic Ras cheese rich in conjugated linoleic acid (CLA) was investigated using probiotic Lactobacillus casei and Lactobacillus acidophilus starters. The cheeses were assessed for composition, proteolysis, fatty acids and fat stability, and microbiology during 3 months of ripening. The cheese made with Lb. casei and Lb. acidophilus retained high counts of the probiotic strains (∼log 8) throughout storage. Ripening changes followed the normal pattern of this type of cheese during ripening. Ras cheese made with Lb. casei and Lb. acidophilus contained the highest CLA content (0.84% after 3 months) as compared to control and cheese fat had acceptable oxidative stability.

Characterization of a new isolate of Lactobacillus fermentum IFO 3956 from Egyptian Ras cheese with proteolytic activity

More than 200 isolates were obtained from 15 Egyptian traditional dairy products (Domiatti cheese, Ras cheese and Rayeb milk) collected from local markets of Alexandria, Tanta and Kafr El-Sheikh. Examination with optical microscope of these dairy samples allowed to classify 92 bacilli, 64 of which were identified as lactobacilli. The proteolytic activity of lactobacilli isolates was tested on skim milk agar. Eight isolates showing a high proteolytic activity were further tested on UHT skim milk. The strain showing the highest proteolytic activity was purified and identified as Lactobacillus fermentum IFO 3656. The specific proteolytic activity of this strain and the factors affecting it (pH, temperature and presence of inhibitors) were studied. The proteolysis targeted mainly caseins (73% of whole casein), especially β-casein (85%). Smaller portions of whey proteins were proteolyzed (20%) essentially β-lactoglobulin. The proteolysis process gave rise to medium-sized peptide populations. The optimum conditions for the proteolysis activity of the studied strains were pH 6.5 and 37 °C. Proteolytic activities were very slightly affected by the increase of the temperature to 42 °C or the pH to 8.2. The protease system of Lactobacillus fermentum IFO 3956 is most probably composed from a high amount of metalloproteases and small amount of cysteine and serine proteases.

USING ACIDULANTS IN MAKING RICOTTA CHEESE FROM SWEET AND SALTED WHEY

Ricotta cheese was made from sweet or salted whey produced from Ras cheese whey by heat coagulant and direct acidification. Acetic ,citric or lactic acid were used to adjust the pH to 5.8- 5.9 at 87 -88˚c. Cheese made using lactic acid had a higher yield compared with other acid coagulant. Also, cheese treated with acetic acid had the highest total solids and protein content than that from other treatments, either made from sweet or salted whey. In addition ,cheese made by using heat coagulant had the highest fat content, either made from sweet or salted whey. On the other hand, cheese treated with acetic acid had a higher scoring points. Moreover, cheese made by using heat coagulant had lower total bacterial count (T.C), proteolytic and lipolytic bacterial counts either made from sweet or salted whey. However, cheese made by using acetic acid had the lowest counts of moulds and yeasts (M&Y).

IMPROVEMENT OF QUALITY OF RAS CHEESE MADE FROM PASTEURIZED MILK USING A SPECIAL SLURRY FROM EWE'S MILK

The present study was carried out as an at-tempt to improve the quality of Ras cheese made from pasteurized cow's milk using ewe's milk slurry to which proteases and lipases were added. The slurry was incubated at 30oC for one week, and then added either to the cheese milk prior to coag-ulation or directly to the cheese curd before press-ing. Cheeses were analysed for chemical, microbi-ological and organoleptic properties at 0, 15, 30, 60 and 90 d of ripening. Generally, the addition of slurry affected at least four parameters of interest for the flavour development. Cheese flavour devel-opment was accelerated, the proteolysis was en-hanced and casein breakdown was stimulated. Addition of slurry increased the levels of the total volatile fatty acids at each period of ripening, par-ticularly with addition of slurry to cheese curd. Ad-dition of slurry affected the microbiological quality of cheeses. Proteolytic and lipolytic bacterial counts increased throughout ripening, while yeast and moulds were no longer detectable in slurry added cheese after 30 d of ripening. Sensory eval-uation showed that the Ras cheeses made with the slurry received higher scores for flavor and body and texture than the control cheese over 90 d of ripening. These results suggested that the addition of ewe's milk slurry was necessary for develop-ment of sensory characteristics of the cheeses.

InfluenceofMilkTreatmentandAdjunctCulture on Quality of Ras Cheese

InfluenceofMilkTreatmentandAdjunctCulture on Quality of Ras Cheese

The effect of Egyptian honeybee propolis on the growth of Aspergillus versicolor and sterigmatocystin biosynthesis in Ras cheese

Propolis is a natural product collected by honeybee workers. The product was tested for its antifungal effect against Aspergillus versicolor ATCC 12996 as well as biosynthesis of sterigmatocystin during ripening of Egyptian Ras cheese. The use of different concentrations of aqueous propolis extract 250, 500 and 1000 part per million (ppm) on the cheese surface was investigated. Mould growth and toxin production were completely inhibited at the highest concentration 1000 ppm, while the lower concentrations exhibited definite fungistatic activity during 90 days of ripening. Control cheese demonstrated that the amount of sterigmatocystin produced was proportional to the growth of Asp. versicolor during three months of ripening. It could be concluded that propolis concentration of 1000 ppm could prevent mould growth and sterigmatocystin production in Ras cheese. The economic as well as the public health importance of propolis as a natural preservative in cheese manufacture is discussed.

Evaluation of isolated starter lactic acid bacteria in Ras cheese ripening and flavour development

Eighteen cultures of starter lactic acid bacteria with or without added adjunct cultures, isolated from Egyptian dairy products, were evaluated in experimental Ras cheese for flavour development. Chemical composition of experimental cheeses was within the legal limit for Ras cheese in Egypt. All cultures used in this study had no effect on chemical composition of Ras cheese. Very significant variations in free amino acids, free fatty acids and sensory evaluation have been found among the cultures used in Ras cheesemaking. The levels of free amino acids and free fatty acids were correlated well with flavour development in Ras cheese. Seven of the tested cultures produced acceptable flavour and texture of Ras cheese. The highest overall score of flavour intensity, flavour and texture acceptability were in cheese made using YY47 lactic culture in addition to adjunct culture of Lactobacillus helveticus, Lactobacillus paracasei subsp. paracasei, Lactobacillus delbrueckii subsp. lactis and Enterococcus faecium. This culture can be recommended for Ras cheese manufacture using pasteurized milk.

Characterisation of lactic acid bacteria isolated from artisanal Egyptian Ras cheese

Des souches sauvages de Lactococcus, Lactobacillus, Enterococcus et Pediococcus ont ete isolees a partir du fromage egyptien « Ras ». Les souches furent ensuite caracterisees d'apres leur aptitude technologique et biochimique. Lactococcus lactis subsp. lactis et cremoris se developpaient a 40 °C en presence de 4 % Nacl. Six souches de Lactococcus lactis subsp. lactis et une souche de Lactococcus lactis subsp. cremoris ainsi que 95 % des souches de Lactobacillus etaient resistantes au chlorure de sodium a des concentrations de 6,5 %. Environ 20 % des lactocoques, 21 % des lactobacilles et 43 % des enterocoques montraient une activite acidifiante moyenne. La majorite des lactobacilles possedaient une forte activite autolytique et aminopeptidasique. Vingt-sept pourcent des souches testees montraient une activite inhibitrice vis-a-vis des autres souches. La plus forte activite inhibitrice a ete revelee chez les enterocoques. La production d'exopolysaccharides a ete demontree chez 4,8 % des lactobacilles. En regle generale, les souches qui montraient des caracteristiques interessantes ont ensuite etait selectionnees pour la production de composes d'arome dans le lait. Quatre-vingt-onze souches ont ete isolees et selectionnees pour la fabrication de fromage Ras en fonction de leur tolerance au sel, croissance a 40-45 °C, production d'acide, activite proteolytique, production d'aromes et de bacteriocines. Ces souches seront testees a l'echelle pilote pour fabriquer du fromage Ras.

PROBIOTIC BACTERIA AS A TOOL TO PREVENT FUNGAL GROWTH AND AFLATOXINS PRODUCTION BY Aspergillus parasiticus

Lactobacillus strains are used as probiotic bacteria in fermented dairy products and other fermented food products, whereas they are known to prolong the shelf life of these products. The inhibitory effect of cell free supernatant (CFS) of several Lactobacillus species on mycelium growth and the aflatoxin production by the aflatoxigenic strain of Aspergillus parasiticus was studied. A complete inhibition (100%) of mycelium growth and aflatoxin production was recorded when cell free supernatant of Lactobacillus casei was placed in a dialysis sac or in the medium without a dialysis sac or on the insertion of A. parasiticus after 16 hours with L. casei. Both L. reuteri and L. gasseri inhibited mycelium growth and aflatoxin production but to a lesser extent. Cell free supernatant of L. acidophilus and L. bulgaricus showed the lowest effect on aflatoxin production as well as on mycelium growth. The inoculation of bacterial strains of L. casei, L. gasseri and L. reuteri before fungal growth inoculation by 16 hours caused inhibitory effects on mycelium growth and aflatoxin production. But these indications were not observed for the other treatments of L. acidophilus or L. bulgaricus. The probiotic strains (L. casei, L. reuteri) with higher antifungal activity were used and incorporated in the manufacture of Ras cheese to replace the normal starters (S. thermophilus, L. bulgaricus), where they prevented the growth of fungi during the three month of the storage period. In conclusion probiotic bacteria may be able to produce active substances that can inhibit aflatoxins production by A. parasiticus in most treatments used, and the inhibitory effect depends on the type of lactic acid and / or the treatment used.

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.

Physical and Sensory Properties of Block Processed Cheese with Formulated Emulsifying Salt Mixtures

Various emulsifying salt mixtures were used in making block type processed cheeses. Ras cheese was used as the cheese base with two salt mixtures: (i) Na-diphosphate + Na-polyphosphate + Na-tripolyphosphate and (ii) Na-poly-phosphate + Na-citrate + Na-orthophosphate + Na-diphosphate comparing to commercial salts Joha SE and PZO respectively. The resultant processed cheeses were analyzed when fresh and monthly during storage at 7 and 20°C for water activity (a w ), oil separation, meltability, flow behavior, color parameters, and sensory properties. There were no significant differences in water activity values among all treatments. The differences were significant in oil index and meltability values. The samples exhibited different shear stress values and it was highest in treatments with commercial salts. Consistency coefficient (k-value) of processed cheese samples was affected by emulsifying salt mixture being almost two folds higher with salt mixtures (i) than those of salt mixtures (ii). The color parameters L, a, b, Chroma and hue angle showed slight differences among treatments and the cheese was shinier and whiter with increasing pyrophosphate content in the salt mixture. The stored samples became less white especially when stored at room temperature (20°C). Sensory evaluation showed that all cheeses were acceptable but the most acceptable samples were produced with mixtures in the ratio of (i) 30:40:30 and (ii) 50:20:20:10.

Characterisation of Egyptian Ras cheese. 2. Flavour formation

Thirteen samples of commercial Ras cheese made from raw milk at different ripening-times were collected to evaluate the sensory properties and to identify the typical flavour compounds. Cheeses were assessed by sensory evaluation and the rheological properties were determined using a texture analyser. The flavour volatile compounds were identified by the purge-and-trap, thermal desorption cold-trap (TDCT), and gas chromatography mass spectrometry (GC-MS). The sensory results indicated that nine samples were typical Ras cheeses and four samples were not typical. Typical Ras cheeses are tasty, piquant and sharp in flavour, not too hard and not soft in texture and the body includes some mechanical opening and gassy opening and the colour is regular. A good correlation was found between the rheological measurements calculated by machine and the texture score evaluated by panellists. GC-MS analysis revealed that, sixty-eight volatile compounds were detected in Ras cheese samples, including 13 alcohols, 11 aldehydes, 17 ketones, 25 esters and four other compounds, which are responsible for the cheese flavour. There were differences in the concentrations of these aroma-compounds, corresponding with the age of the cheeses. GC-MS data showed a good correlation with the organoleptic descriptions.

Isolation, identification and selection of lactic acid bacteria cultures for cheesemaking

Lactic Acid Bacteria (LAB), which are considered to be the most useful microorganisms to society, are involved in the manufacture of thousands of fermented foods.<br>They are also beneficial in flavoring foods, inhibiting pathogenic as well as spoilage bacteria in these products. A total of 2000 isolates of LAB were obtained from traditional Egyptian dairy products (different types of raw milk, ras, domiatti and kareish cheese, mish, cream, butter and fermented milk such as laban, rayeb and zabady) obtained from different regions in Egypt. The pre-identification tests were performed according to the morphological characteristics: catalase test, growth at 10°C and 45°C, growth in the presence of 6.5% NaCl and Co2 production. The isolates were subjected to phenotypic and cell wall protein characterization analyses. Phenotypically, 1006 strains were identified using API 50 CHL and API 20 Strep (Apparatus and procedure of identification). The SDS-PAGE technique (Sodium dodycyl sulfate) of whole cell protein was evaluated as an advanced tool for the identification of LAB. Therefore protein fingerprints were registered for 514 strains and compared to a large number of LAB reference<br>strains stored in database format. The SDS-PAGE technique confirmed 94% of the API<br>identification results. The identified strains were tested for acidifying activity, autolytic and<br>aminopeptidase properties, antagonistic activities and polysaccharides production.<br>Selected cultures where then evaluated as starter or adjunct cultures for Ras and Domiatti cheese production in the cheese research laboratory. Higher cheese flavor scores were consistently obtained in Ras cheese made with cultures showing high peptidase and esterase activity and a high rate of autolysis. Development of free amino acids and free fatty acids in Ras cheese were always higher when compared to the cheese made using other starters.

INCORPORATION OF BUTTERMILK WITH OTHER MILKS IN RAS CHEESE PRODUCTION. J. BUFFALOE'S MILK USING TWO TYPES OF RENNET

INCORPORATION OF BUTTERMILK WITH OTHER MILKS IN RAS CHEESE PRODUCTION. J. BUFFALOE'S MILK USING TWO TYPES OF RENNET