Determination of cow milk-casein in sheep and goat cheese by immunoelectrophoresis

By means of crossed immunoelectrophoresis according to the method of Clarke and Freeman combined with a modification of the silver staining technique of Willoughby and Lambert, using a commercial anti-bovine casein rabbit serum, in sheep's and goat's cheese it is possible to evaluate the added cow's milk in a clear and reproducible way down to a level of 0.1-0.2%. The lower detection limit is within the lower scale after the addition of starter cultures usual in the production of cheese from raw milk and more than tenfold below the amounts of starter cultures used in the production of cheese from heated milk. Because of the possibility of using casein for detection, this method is suitable for analysis, not only in cheese made from raw milk, but also in that made from heated milk.     

Detection of milk powder and caseinates in Halloumi cheese

Halloumi cheese is traditionally manufactured from fresh milk. Nevertheless, dried dairy ingredients are sometimes illegally added to increase cheese yield. Lysinoalanine and furosine are newly formed molecules generated by heating and drying milk protein components. The levels of these molecular markers in the finished Halloumi have been investigated to verify their suitability to reveal the addition of skim milk powder and calcium caseinate to cheese milk. Because of the severe heating conditions applied in curd cooking, genuine Halloumi cheeses (n = 35), representative of the Cyprus production, were characterized by levels of lysinoalanine (mean value = 8.1 mg/100 g of protein) and furosine (mean value = 123 mg/100 g of protein) unusual for natural cheeses. Despite the variability of the values, a good correlation between the 2 parameters (R = 0.975) has been found in all cheeses, considering both the fresh and mature cheeses as well as those obtained from curd submitted to a prolonged cooking following a traditional practice adopted by a very small number of manufacturers. Experimental cheeses made by adding as low as 5% of skim milk powder, or calcium caseinate, or both, to cheese milk fell outside the prediction limits at ±2 standard deviation of the above-reported correlation regardless of curd cooking conditions or ripening length. This correlation may be adopted as a reliable index of Halloumi cheese genuineness.     

Comparison of the characteristics of teleme cheese made from ewe's, goat's and cow's milk or a mixture of ewe's and goat's milk

Teleme cheeses were manufactured from ewe's, goat's and cow's milk and mixture of ewe's and goat's milk. Physicochemical and biochemical analyses of the cheeses at various stages of ripening and storage were performed. Cheeses made from goat's milk had lower moisture content than those made from other milks. No significant differences in the mean values of protein, salt and water activity (a _w ) of the different cheeses at all ages studied were found. Cheeses from goat's and cow's milk had higher contents of fat and fat in dry matter (FDM) compared to that of cheeses from ewe's milk and mixed milk. Significant differences were observed in the yield and yield on 56% moisture: cheeses from ewe's milk gave the highest yield and cheese from cow's milk the lowest. Significant differences were found in the ashes content of the different cheeses at all ages. No differences in cholesterol and cholesterol/fat contents of the four types of cheeses were found. Main and trace elements showed variability among the four cheeses.     

Assessment of the colorimetric and fluorometric assays for alkaline phosphatase activity in cow's, goat's, and sheep's milk

Raw milk is a well-established vehicle for the carriage of human pathogens, and many regulatory bodies have consequently mandated compulsory pasteurization as a food safety intervention. The residual activity of alkaline phosphatase (ALP) has historically been used to verify the adequacy of pasteurization of cow's milk. However, there is uncertainty on how the current ALP standards and methods of analysis can be applied to sheep's and goat's milk, which naturally contain different levels of the enzyme than that found in cow's milk. The official ALP methods applied in Canada (colorimetric assay; MFO-3) and in the United States (Fluorophos) were assessed for their ability to detect enzyme activity in raw and pasteurized milk derived from cows, sheep, and goats. The detection limit and the limit of quantitation were 0.8 and 2.02 microg/ml phenol, respectively, for the MFO-3 method and 43 and 85 mU/liter, respectively, for the Fluorophos method. The average ALP levels in raw goat's, cow's, and sheep's milk were 165, 1,562, and 3,512 microg/ml phenol, respectively. Raw milk detection limits, which correspond to raw milk phosphatase levels, were 0.051, 0.485, and 0.023% in cow's, goat's, and sheep's milk, respectively, for the MFO-3 method and 0.007, 0.070, and 0.004%, respectively, for the Fluorophos method. Although both methods can be used for ALP determination in cow's, goat's, and sheep's milk, the Fluorophos assay was superior to the colorimetric MFO-3 method based on sensitivity and time required to complete the analysis.     

Nachweis von Kuhmilch in Schaf- und Ziegenmilch bzw. -k?se durch isoelektrische Focussierung in harnstoffhaltigen Polyacrylamidgelen

Summary Addition of cow's milk to sheep's and goat's milk or cheese can be detected by isoelectric focusing of acid caseins on thin layers of polyacrylamide gels containing 6 M urea. From densitometric evaluation of protein pherograms, taking a-casein as indicator protein, presence of cow's milk can be determined with confidence down to a level of 2 or 1% in sheep's or goat's milk. Some commercially available cheeses from goat's or sheep's milk were found to contain large amounts of cow's milk. Advantages of the present method as compared to immunological methods are discussed.Zusammenfassung Ein Zusatz von Kuhmilch zu Schaf und Ziegenmilch oder -käse kann durch isoelektrische Focussierung der Säurecaseine auf dünnen, harnstoff haltigen Polyacrylamidgelen (PAGIF) nachgewiesen werden. Bei quantitativer, densitometrischer Auswertung der Pherogramme unter Verwendung eines-Caseins als Indikatorprotein l:aßt sich Kuhmilch in Schaf oder Ziegenmilch bis herab zu 2 bzw. 1% sicher nachweisen. In einigen Ziegen- und Schafkäsen des Handels konnte die Verwendung von Kuhmilch eindeutig festgestellt werden. Vorteile dieser Methode gegenüber den immunologischen Verfahren werden erörtert.     

EVALUATION OF pH CHANGE KINETICS DURING DIFFERENT STAGES OF KASHAR CHEESE PRODUCTION FROM BOVINE, OVINE AND CAPRINE MILK

The objective of this study was to determine the pH change kinetics during Kashar cheese production from bovine, ovine and caprine milk. Kinetics of pH change were determined during milk ripening, cooking/holding and pressing/fermentation phases of Kashar cheese. The pH decreased logarithmically, nonlinearly, with time in the milk ripening period and was reduced linearly with time in the cooking/holding and pressing/fermentation stages. The time of pH decrease in cow's, ewe's and goat's milk was significantly different, except cooking/holding time, for three stages. There was no difference between bovine and caprine milk in cooking/holding time; however, ovine milk was significantly different from the other two kinds of milk. The shortest and the longest overall times were determined for caprine and ovine milk cheeses, respectively. The rate of change in milk pH of the three species was significantly different for three stages. The rate followed the pattern caprine  >  bovine  >  ovine milk.

PRACTICAL APPLICATIONS

Optimum acid development is essential to creating the desired cheese mass. For each major cheese type, lactic acid must develop in the appropriate time, usually not too rapidly or too slowly, and in a specific concentration. The progress of acidification is monitored by pH change in the industrial Kashar cheese production. The final pH of cheese is determined not only by the amount of lactic acid but also by the buffering capacity (BC) of the milk and curd. However, the BC is different between milk species. This study evaluates and compares the pH change kinetics during various stages of Kashar cheese making using cow's, ewe's and goat's milk. This work may help to compare milk and cheese curds made from bovine, ovine and caprine milk.     

Prediction of the percentages of cows', goats' and ewes' milk in “Iberico” cheese by electrophoretic analysis of whey proteins

Stepwise multiple linear regression (SMLR) and principal components regression (PCR) have been used to predict the percentages of cows', goats' and ewes' milk in “Iberico” cheese, using the results obtained by electrophoretic analysis (PAGE and IEF) of whey proteins, using standard cheeses. Similar predictions of the percentages of milks from the three species were obtained when either SMLR or PCR were applied to the electrophoretic data, i.e. the optical intensity of the electrophoretic bands (PAGE or IEF) of the whey proteins. The root mean square error of prediction in cross-validation (RMSEPCV) was lower than 4% in all cases.     

Low incidence of foodborne pathogens of concern in raw milk utilized for farmstead cheese production

Overall milk quality and prevalence of four target pathogens in raw milk destined for farmstead cheesemaking was examined. Raw milk samples were collected weekly from June to September 2006 from 11 farmstead cheese operations manufacturing raw milk cheese from cow's, goat's, and sheep's milk. Samples were screened for Listeria monocytogenes, Staphylococcus aureus, Salmonella, and Escherichia coli O157:H7 both quantitatively (direct plating) and qualitatively (PCR). Overall, 96.8% of samples had standard plate counts of < 100,000 CFU/ml, 42.7% of which were < 1,000 CFU/ml. Although no federal standards exist for coliforms in raw milk, 61% of samples tested conformed to pasteurized milk standards under the U.S. Pasteurized Milk Ordinance (PMO) at < 10 CFU/ml. All cow and sheep milk samples and 93.8% of goat milk samples were within the limits dictated by the PMO for somatic cell counts. Of the 11 farms, 8 (73%) produced samples that were positive for S. aureus, which was detected in 34.6% (46 of 133) of milk samples. L. monocytogenes was isolated from three milk samples (2.3%), two of which were from the same farm. E. coli O157:H7 was recovered from one sample of goat's milk for an overall incidence of 0.75%. Salmonella was not recovered from any of the 133 samples. The findings of this study suggest that most raw milk intended for farmstead cheesemaking is of high microbiological quality with a low incidence of pathogens. These data will help inform risk assessments associated with the microbiological safety of farmstead cheeses, particularly those manufactured from raw milk.     

Influence of fat, heat treatments and species on milk rennet clotting properties and glycomacropeptide formation

The influence of species, fat and heat treatment (70 °C for 30 min) of milk on rennet clotting time, k₂₀ value (time as the curd is firm enough to be cut) and glycomacropeptide formation was studied. Rennet clotting properties were affected by the three studied factors. The results obtained could indicate that the fat and the heat treatment have a different influence in the rennet clotting properties of cow's, ewe's and goat's milks; however, those differences, although significant, are not high and its influence in cheese manufacture perhaps have not a great importance. The slope of the glycomacropeptide formation as a function of the incubation time of milk with rennet was calculated applying a linear regression analysis. The slope decreased significantly when whole or skim cow's milk was heated indicating a slower glycomacropeptide formation. Fat and heat treatments had no significant influence on glycomacropeptide formation of ewe's and goat's milk. The results obtained indicate that the fat concentration and the fat globule membrane could influence the initial aggregation of the destabilised casein micelles.     

Bestimmung von Kuhmilch-Casein in Schaf- und Ziegenk?se mittels Immunelektrophorese

Zusammenfassung Durch Kombination der Kreuzimmunelektrophorese nach Clarke u. Freeman mit einer Modifikation der Silberfärbung nach Willoughby u. Lambert wird es unter Verwendung eines käuflichen Antiserums gegen Rindercasein möglich, bei der Herstellung von Schaf- und/oder Ziegenkase zugesetzte Kuhmilch bis zu der unteren Grenze von 0,1–0,2% eindeutig und reproduzierbar zu bestimmen. Die Nachweisgrenze liegt damit im unteren Größenord-nungsbereich des Starterkulturenzusatzes bei der Herstellung von Rohmilchkäsen und sogar um mehr als das 10fache unter den Mengen an Starterkulturen, wie sie zur Käseherstellung aus erhitzter Milch eingesetzt werden. Durch die Möglichkeit Casein als Bestimmungsgröße zu verwenden, ist die Methode zur Untersuchung von Käsen aus Rohmilch sowohl als auch von solchen aus erhitzter Milch hergestellten in gleicher Weise geeignet.

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Detection of bovine casein in sheep and goat milk cheese by means of immunoelectrophoresis

Summary By means of crossed immunoelectrophoresis according to the method of Clarke and Freeman combined with a modification of the silver staining technique of Willoughby and Lambert, using a commercial anti-bovine casein rabbit serum, in sheep's and goat's cheese it is possible to evaluate the added cow's milk in a clear and reproducible way down to a level of 0.1–0.2%. The lower detection limit is within the lower scale after the addition of starter cultures usual in the production of cheese from raw milk and more than tenfold below the amounts of starter cultures used in the production of cheese from heated milk. Because of the possibility of using casein for detection, this method is suitable for analysis, not only in cheese made from raw milk, but also in that made from heated milk.

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Die vorliegende Arbeit wurde aus Mitteln der Mitverantwortungsabgabe von der Kommission der Europäischen Gemeinschaft in Brüssel finanziell unterstützt     

Content of taurine in Apulian Cacioricotta goat's cheese

 Taurine (Tau) is a sulfonated amino acid which is not incorporated into polypeptide structures and whose importance in the growth of newborns and young children has been well established. It is the most abundant free amino acid in goat's milk, where it occurs in higher amounts than in other kinds of milk. Tau and other free amino acids were analysed by high-performance liquid chromatography in Apulian Cacioricotta goat's cheese. Tau was present in both fresh and ripened cheese, providing a new reason for enhancing the value of this typical local dairy product. Received: 5 August 1999 / Revised version: 14 September 1999     

Major and trace elements in milk and Halloumi cheese as markers for authentication of goat feeding regimes and geographical origin

Sixty samples of milk, Halloumi cheese and local grazing plants (i.e. shrubs) were collected over a year from dairy farms located on three different locations of Cyprus. Major and trace elements were quantified using inductively coupled plasma–atomic emission spectroscopy (ICP‐AES). Milk and Halloumi cheese produced in different geographical locations presented significant differences in the concentration of some of the elements analysed. Principal component analysis showed grouping of samples according to the region of production for both milk and cheese samples. These findings show that the assay of elements can provide useful fingerprints for the characterisation of dairy products.     

Immunological estimation of bovine casein in sheep cheese products (author's transl)

Casein fraction of cow's milk and sheep's milk are very similar in their immunological behavior. Therefore, in the presence of sheep's milk, precipitation reaction with commercially obtained serum are not specific. Results from comparative immunoelectrophoresis according to Grabar and Williams also are equivocal, for heat and other denaturing factors caused shifts in the pattern of just the small group of differing elecrophoretic bonds present among many identical bonds. Qualitative identification of large amounts of cow's milk added to sheep's milk or of bovine casein to sheep cheese or similar products are possible in principle by two dimensional immunoelectrophoresis or so called crossed immunoelectrophoresis as described by Clarke and Freeman, but this estimation takes a lot of time and is not suitable for analysis of a series of samples. Sufficient sensitivity for certain and semiquantitative statements about the content of cows' milk casein in products from sheep's milk are obtained by the technique of radial double diffusion by Ouchterlony in Agarose gels only by the saturation of commercial anti-bovine-casein-serum by means of a suitable protein-standardized sheep's milk extract and its subsequent work-up and lyophilisation to yield a stable serum.     

Concentrations of cadmium and lead in different types of milk

 Concentrations of Pb and Cd were determined in samples of human, raw and pasteurized cow's and goat's milk and powdered infant formula. The following mean Cd concentrations (and ranges) were recorded: in human milk, 2.70 μg/l (0.6–11.3, n=55); in raw cow's milk, 4.88 μg/l (0.7–23.1, n=47); in pasteurized cow's milk, 4.30 μg/l (3.4–5.9, n=6); in goat's milk, 7.81 μg/l (1.0–18.4, n=38); and in powdered, infant formula, 3.81 μg/l (3.4–4.1, n=5). The concentrations (and ranges) of Pb were: in human milk, 8.34 μg/l (0.1–32.3, n=55); in raw cow's milk, 14.82 μg/l (1.3–39.1, n=28); in pasteurized cow's milk, 10.25 μg/l (6.9–19.6, n=6); in goat's milk, 11.86 μg/l (0.4–38.5, n=36); and in powdered, infant formula, 8.30 μg/l (5.1–10.6, n=5). Our data were within the normal ranges for each kind of milk. The Cd and Pb concentrations in goat's milk were significantly higher than the concentrations observed in the other milks, whereas human milk and powdered infant formula presented the lowest Cd and Pb concentrations. A considerable decrease in the concentration of Cd with the stage of lactation was observed. The concentrations of Cd and Pb in human, cow's and goat's milk also varied according to the time of year. The concentrations of Pb and Cd in the different milks did not present any risk to human health (infants or adults). Received: 26 May 1998     

Some Volatile Plant Compounds in Halloumi Cheeses made from Ovine or Bovine Milk

The volatile flavour componds in commercial samples of fresh Halloumi cheese made from either bovine milk or a mixture of ovine and caprine milks were compared. Terpenes, such as α-pinene, β-pinene, copaene, thymol, α-caryophyllene, β-caryophyllene and δ-cadinene were all present in the ovine/caprine cheeses and, in some cases, at concentrations above their reported flavour threshold values. Only low levels of α-pinene and β-caryophyllene were found in the bovine samples, along with D -carvone and eucalyptol from mint added during manufacture. Analysis of some plants that dominated the feeds of the sheep/goats or cows that produced the original milk indicated that the terpenes are likely to have originated in the plants eaten by the animals. It was suggested that the presence of the terpenes may explain the preference of some consumers for the fresh ovine/caprine cheese.     

Impact of milk preacidification with CO2 on the aging and proteolysis of cheddar cheese

To determine the influence of milk preacidification with CO(2) on Cheddar cheese aging and proteolysis, cheese was manufactured from milk with and without added CO(2). The experiment was replicated 3 times. Carbon dioxide (approximately 1600 ppm) was added to the cold milk, resulting in a milk pH of 5.9 at 31 degrees C in the cheese vat. The starter and coagulant usage rates were equal for the control and CO(2) treatment cheeses. The calcium content of the CO(2) treatment cheese was lower, but no difference in moisture content was detected. The higher CO(2) content of the treatment cheeses (337 vs. 124 ppm) was maintained throughout 6 mo of aging. In spite of having almost one and a half times the salt-in-moisture, proteolysis as measured by pH 4.6 and 12% trichloroacetic acid soluble nitrogen expressed as percentages of total nitrogen, was higher in the CO(2) treatment cheeses throughout aging. The ratio of alpha(s)-casein (CN) to para-kappa-CN decreased faster in the CO(2) treatment cheeses than in the control cheeses, especially before refrigerated storage. No difference was detected in the ratio of beta-CN to para-kappa-CN between the control and CO(2) treatment cheeses. Intact alpha(s)- and beta-CN were found in the expressible serum (ES) from the CO(2) treatment cheese as well as alpha(s1)-I-CN, but they were not detected in the ES from the control cheese. No CN was detected in the ES from the curd before the salting of either the control or CO(2) treatment cheese. Higher proteolysis in the cheese made from milk preacidified with CO(2) may have been due to increased substrate availability in the water phase or increased chymosin activity or retention in the cheese.     

The fatty acid composition of Iraqi ewe's, goat's and cow's milk fat

The analysis of the fatty acid composition of 6 samples of the milk fat of each ewes and goats and of 3 samples of the milk fat of cows was accomplished using Hewlett-Packard gas-liquid chromatograph Model 5711 A, provided with an electronic integrator Model 3380. Separation of the methyl esters was performed on columns of 10% sailor on Chromosorb. Temperature programming between 100 degrees C and 180 degrees C was used. The milk fats were qualitatively similar but differed quantitatively. Both ewe's and goat's milk fat had a greater amount of short-chain fatty acids than cow's milk fat. Goat's milk fat contained a higher percentage of short-chain fatty acids compared to that of ewe's milk fat and of goat's milk fat reported in the literature.     

Effect of lecithin addition on the yield and quality of soft cheeses

The effect of lecithin added at levels of 0.025 %, 0.050 % and 0.075 % to cheese milk used in manufacture of Domiati and Kareish cheese on yield, weight losses and quality of cheese was studied. Addition of lecithin increased cheese yield and decreased weight losses during pickling. The bacterial content of all cheeses treated with lecithin was higher than that of control cheese when fresh and during pickling. Cheese made with added lecithin showed higher moisture, salt, fat, and acidity than control cheese. The total nitrogen percentage was almost the same in all treatments. The levels of both soluble nitrogen and total volatile fatty acids in cheese containing lecithin were higher than in the control cheese. No marked differences were evaluated for flavour, body and texture of fresh cheese made from milk with or without lecithin, while during pickling the organoleptic properties of cheese containing lecithin were improved.     

Comparative performance of a mixed strain starter in cow's milk, ewe's milk and mixtures of these milks

Lactococcus lactis ssp. lactis IPLA 947, L. lactis ssp. lactis biovar. diacetylactis IPLA 838 and Leuconostoc citreum IPLA 616 and designed for Afuega'l Pitu cheese manufacture from pasteurized milk was assayed in cow's and ewe's milk, and in mixtures containing 10% and 20% ewe's milk in cow's milk. The evolution of microbial counts, pH, titratable acidity, organic acids and volatile compounds production throughout the incubation period was determined. The use of ewe's milk as a culture medium increased the metabolic activity of the starter culture reflected in a higher lactose consumption, significantly higher acidity and some carbon source-derived organic acids and volatile compounds production, as well as in slightly higher starter strains growth, although the latter was not statistically significant. Thus, it is suggested that ewe's milk or mixtures of ewe's with cow's milk can be satisfactorily used in the manufacture of this traditional cheese. Received: 27 August 1999