Physical properties of cream reformulated with fractionated milk fat and milk-derived components

Emulsifying properties of milk-derived components influence the physical characteristics of reformulated creams. Fractionated butter oils with different melting ranges (low-melt: 10 to 25 degrees C; medium-melt: 25 to 35 degrees C) were recombined into fluid dairy systems using skim milk, or sweet buttermilk and butter-derived aqueous phase to manufacture 20% milk fat creams. Separation temperature (49 degrees C or 55 degrees C) in obtaining emulsifying components was examined for its effect on physical properties of pasteurized reformulated creams. Rate of creaming, viscosity, feathering, and sensory characteristics of reformulated and natural creams stored at 3.3 degrees C were evaluated over a 13-d period. Creaming rate of reformulated and natural creams was unaffected by formulation and was most influenced by duration of storage. Melting characteristics of butter oils influenced viscosity at some shear rates. With the exception of natural cream, all formulations were consistent in apparent viscosity during the 2-wk storage period. All creams feathered in a pH range of 4.70 to 5.20 and were classified as moderately stable to slightly unstable. All reformulated and natural creams met sensory quality specifications with the exception of creams formulated with skim milk and lower melting range butteroil. Creams formulated with buttermilk, butter-derived aqueous phase, and lower-melting range butter oil most closely mimicked natural creams with regard to sensory quality and viscosity.     

Processing effects on physicochemical properties of creams formulated with modified milk fat

Type of thermal process [high temperature, short time pasteurization (HTST) or ultra-high temperature pasteurization (UHT)] and homogenization sequence (before or after pasteurization) were examined for influence on the physicochemical properties of natural cream (20% milk fat) and creams formulated with 20% low-melt, fractionated butteroil emulsified with skim milk, or buttermilk and butter-derived aqueous phase. Homogenization sequence influenced physicochemical makeup of the creams. Creams homogenized before pasteurization contained more milk fat surface material, higher phospholipid levels, and less protein at the milk fat interface than creams homogenized after pasteurization. Phosphodiesterase I activity was higher (relative to protein on lipid globule surface) when cream was homogenized before pasteurization. Creams formulated with skim milk and modified milk fat had relatively more phospholipid adsorbed at the milk fat interface. Ultra-high-temperature-pasteurized natural and reformulated creams were higher in viscosity at all shear rates investigated compared with HTST-pasteurized creams. High-temperature, short time-pasteurized natural cream was more viscous than HTST-pasteurized reformulated creams at most shear rates investigated. High-temperature, short time-pasteurized creams had better emulsion stability than UHT-pasteurized creams. Cream formulated with buttermilk had creaming stability most comparable to natural cream, and cream formulated with skim milk and modified butteroil was least stable to creaming. Most creams feathered in a pH range of 5.00 to 5.20, indicating that they were moderately stable to slightly unstable emulsions. All processing sequences yielded creams within sensory specifications with the exception of treatments homogenized before UHT pasteurization and skim milk formulations homogenized after UHT pasteurization.     

Buttermaking and the churning of blended fat emulsions

The methods used to manufacture butter (the Fritz process and batch-wise churning) basically transform cream into butter grains and buttermilk by agitation and by beating air into the cream. Electron micrographs have been used to show the individual stages of buttergrain formation (ie, phase reversal from oil-in-water into water-in-oil):(1) building up foam from the skim milk, (2) adsorption of fat globules at the foam lamellae and (3) agglomeration of fat globules, (4) destabilization of the foam and mechanical clumping of the agglomerates to form butter grains. The microstructure of the butter grains as well as of the finished butter is characterized by a dispersion of water, air, fat crystals and fat globules in oil. By contrast, margarine has a more homogeneous structure. It does not contain globular fat. Thus the texture of butter tends to be solid, while that of margarine tends to be greasy. The consistency of butter can be influenced to a large extent by temperature treatment of the cream (physical cream ripening). A simple device has been developed for optimizing physical cream ripening which automatically records the melting and crystallization curves of the fat. Many raw material, process and machine specific parameters affect the efficiency of churing as well as the quality of butter, and many of these parameters exert an opposite effect. They therefore have to be set carefully so that they balance each other as required. Dosage of buttermilk and dried skim milk into the product stream has allowed the fat content of butter to be reduced to 60% and the water content to be increased to 36% without impairing product quality. This method has been developed further (Pasilac) for manufacturing a stable, long keeping half-fat and quarter-fat butter (the latter in only a few experiments so far). The structure of these products is not of the oil-in-water dispersion type. It could be characterized as a water-in-oil/fat dispersion, which contains an additional locally continuous aqueous phase. The Alfa buttermaking process (which was used during the 1950s and early 1960s) has recently been revived for the production of the Swedish mixed spread, Bregott, in order to minimize fat losses and to increase further maximum levels of oil inclusion in the blend. Blended spreads comprising milk fat (60­75%) + vegetable oil (25­40%) are no doubt more spreadable than butter at refrigerator temperature. However, they have proved to be too soft above 16­18°C. Therefore experiments have been undertaken to improve the consistency of blended spreads by using different milk fat fractions. In order to preserve the butter character artificial creams have been prepared and churned. The fat mixtures were emulsified in skim milk. Distilled unsaturated monoglycerides were added to the fat phase at different concentrations (0­2%) to make the emulsions sufficiently unstable at low temperatures. Beyond a certain monoglyceride concentration the emulsions could be churned successfully. However, below this critical concentration (which corresponds to roughly half of the mass required for covering all fat globules with monolayers) churning efficiency decreased significantly. Electron micrographs elucidate the mechanism of destabilizing the cream by monoglycerides. Electron micrographs also reveal the globular structure of the products thus obtained. Globular structures are known to cause the typical butter like mouth feel. The firmness/temperature curves of spreads obtained by churning adequately blended fat emulsions could be improved over those of butter (ie, flattened and shifted). In addition, the consistency, as in the case of ordinary butter, could equally be influenced by physical cream ripening.     

Reduction of salt (NaCl) losses during the manufacture of cheddar cheese

The objective of this study was to evaluate the effects of cheese-making technologies, including homogenization of cream, ultrafiltration, and vacuum condensing of milk, on the retention of salt in Cheddar cheese. One part of pasteurized, separated milk (0.58% fat) was ultrafiltered (55 degrees C, 16.0% protein), another vacuum condensed (12.5% protein), and the third was not concentrated. Cheddar cheese was manufactured using 6 treatments by standardizing unconcentrated milk to a casein-to-fat ratio of 0.74 with unhomogenized 35% fat cream (C), homogenized (6.9 MPa/3.5 MPa) 35% fat cream (CH), ultrafiltered milk and unhomogenized cream (UF), ultrafiltered milk and homogenized cream (UFH), condensed milk and unhomogenized cream (CM), and condensed milk and homogenized cream (CMH). Treatments C and CH had 3.7% fat and 3.5% protein, and the respective values for the remaining treatments were 4.9 and 4.6. The milled curd was dry salted at 2.7% by weight. The salt content of the cheeses receiving homogenization treatment was higher at 1.83 and 1.70% for CH and UFH, respectively, compared with their corresponding controls at 1.33%. The salt content in cheeses from CMH was 1.64% and was not affected by homogenization. Salt retention in C increased from 41.7 to 59.2% in CH, and in UF it increased from 42.5 to 54.5% in UFH. There was a corresponding decrease in the salt content of whey from these cheeses.     

FULLY HYDROGENATED VEGETABLE OIL AS A STABILIZER FOR LOW FAT BUTTER SPREADS

A blend containing hydrogenated fat and a liquid oil was used for preparation of low fat butter spreads. The effects of maltodextrin (MD), skim milk powder (SKMP), guar gum and fully hydrogenated (hardened) vegetable oil on spreadability and phase separation of low fat butter spreads with 30% water were studied. Oil separation in bulk storage and on centrifugation in spreads containing MD, SKMP and guar gum was observed. However, the products prepared by incorporation of 2% hardened oil did not show any oil separation at 25 or 36C. The fat content of the spreads was reduced to 57% by incorporating MD or SKMP along with hardened oil. The spreads showed better spreadability at refrigerated temperatures and better stand up properties at high storage temperatures compared to commercial butter.     

Effects of milk fat, cocoa butter, or selected fat replacers on flavor volatiles of chocolate ice cream

Selected volatile compounds of chocolate ice creams containing 0.6, 4.0, 6.0, or 9.0% milk fat or containing 2.5% milk fat, cocoa butter, or one of three fat replacers (Simplesse, Dairy Lo, or Oatrim) were analyzed by gas chromatography and gas chromatography-mass spectrometry using headspace solid-phase microextraction. The headspace concentration of most of the selected volatile compounds increased with decreasing milk fat concentration. Fat replacers generally increased the concentration of volatiles found in the headspace compared with milk fat or cocoa butter. Few differences in flavor volatiles were found between the ice cream containing milk fat and the ice cream containing cocoa butter. Among the selected volatiles, the concentration of 2,5-dimethyl-3(2-methyl propyl) pyrazine was the most highly correlated (negatively) with the concentration of milk fat, and it best discriminated among ice creams containing milk fat, cocoa butter, or one of the fat replacers.     

Serum protein and casein concentration: effect on pH and freezing point of milk with added CO2

The objective of this study was to determine the effect of protein concentration and protein type [i.e., casein (CN) and serum protein (SP)] on pH (0 degree C) and freezing point (FP) of skim milk upon CO2 injection at 0 degree C. CN-free skim milks with increasing SP content (0, 3, and 6%) and skim milks with the same SP content (0.6%) but increasing CN content (2.4, 4.8, and 7.2%) were prepared using a combination of microfiltration and ultrafiltration processes. CO2 was injected into milks at 0 degree C using a continuous flow carbonation unit (230 ml/min). Increasing SP or CN increased milk buffering capacity and protein-bound mineral content. At the same CO2 concentration at 0 degree C, a milk with a higher SP or a higher CN concentration had more resistance to pH change and a greater extent of FP decrease. The buffering capacity provided by an increase of CN was contributed by both the CN itself and the colloidal salts solublized into the serum phase from CN upon carbonation. Skim milks with the same true protein content (3%), one with 2.4% CN plus 0.6% SP and one with 3% SP, were compared. At the same true protein content (3%), increasing the proportion of CN increased milk buffering capacity and protein-bound mineral content. Milk with a higher proportion of CN had more resistance to pH change and a greater extent of FP decrease at the same carbonation level at 0 degree C. Once CO2 was dissolved in the skim portion of a milk, the extent of pH reduction and FP depression depended on protein concentration and protein type (i.e., CN and SP).     

Gamma-glutamyl transpeptidase in milk and butter as an indicator of heat treatment

Naturally present γ-glutamyl transpeptidase (GGTP) in whole and skim milk was inactivated by heat treatment at >79°C for 16 s. Of the total activity in whole milk, 72% was found in the skim milk fraction. Little seasonal variation was noted in either whole or skim raw milk over a period of 300 days. Using a commercially available test kit for GGTP, as little as 0·1% raw milk or cream could be detected in pasteurized skim milk and butter. An alternative GGTP method examined was less sensitive than the commercial method. However, it was necessary for cream products with low GGTP activity since cream interfered with the commercial assay. No reactivation of GGTP was found in whole milk or butter under a variety of conditions. Commercial milk and cream samples were negative for GGTP activity. The results suggest that GGTP analysis could be useful for monitoring the heat-treatment give to fluid milk products.     

Heat resistance of Bacillus cereus spores: effects of milk constituents and stabilizing additives.

Heat resistance of Bacillus cereus spores (ATCC 7004, 4342, and 9818) heated in different types of milk (skim, whole, and concentrated skim milk), skim milk containing stabilizing additives (sodium citrate, monopotassium phosphate, or disodium phosphate, 0.1%), and cream was investigated. Thermal resistance experiments were performed at temperatures within the range of 92 to 115 degrees C under continuous monitoring of pH. For strain 4342 no significant differences (P < 0.05) in D values were detected in any case. For strains 7004 and 9818 higher D values of about 20% were obtained in whole and concentrated skim milk than those calculated in skim milk. From all stabilizing additives tested, only sodium citrate and sodium phosphate increased the heat resistance for strain 9818. However, when the menstruum pH was measured at the treatment temperature, different pH values were found between the heating media. The differences in heat resistance observed could be due to a pH effect rather than to the difference in the substrates in which spores were heated. In contrast, when cream (fat content 20%) was used, lower D values were obtained, especially for strains 7004 and 9818. z values were not significantly modified by the milk composition, with an average z value of 7.95+/-0.20 degrees C for strain 7004, 7.88+/-0.10 degrees C for strain 4342, and 9.13+/-0.16 degrees C for strain 9818.     

Compositional and functional properties of buttermilk: a comparison between sweet, sour, and whey buttermilk

Buttermilk is a dairy ingredient widely used in the food industry because of its emulsifying capacity and its positive impact on flavor. Commercial buttermilk is sweet buttermilk, a by-product from churning sweet cream into butter. However, other sources of buttermilk exist, including cultured and whey buttermilk obtained from churning of cultured cream and whey cream, respectively. The compositional and functional properties (protein solubility, viscosity, emulsifying and foaming properties) of sweet, sour, and whey buttermilk were determined at different pH levels and compared with those of skim milk and whey. Composition of sweet and cultured buttermilk was similar to skim milk, and composition of whey buttermilk was similar to whey, with the exception of fat content, which was higher in buttermilk than in skim milk or whey (6 to 20% vs. 0.3 to 0.4%). Functional properties of whey buttermilk were independent of pH, whereas sweet and cultured buttermilk exhibited lower protein solubility and emulsifying properties as well as a higher viscosity at low pH (pH ≤ 5). Sweet, sour, and whey buttermilks showed higher emulsifying properties and lower foaming capacity than milk and whey because of the presence of milk fat globule membrane components. Furthermore, among the various buttermilks, whey buttermilk was the one showing the highest emulsifying properties and the lowest foaming capacity. This could be due to a higher ratio of phospholipids to protein in whey buttermilk compared with cultured or sweet buttermilk. Whey buttermilk appears to be a promising and unique ingredient in the formulation of low pH foods.     

Milk pH as a function of CO2 concentration, temperature, and pressure in a heat exchanger

Raw skim milk, with or without added CO2, was heated, held, and cooled in a small pilot-scale tubular heat exchanger (372 ml/min). The experiment was replicated twice, and, for each replication, milk was first carbonated at 0 to 1 degree C to contain 0 (control), 600, 1200, 1800, and 2400 ppm added CO2 using a continuous carbonation unit. After storage at 0 to 1 degree C, portions of milk at each CO2 concentration were heated to 40, 56, 72, and 80 degrees C, held at the desired temperature for 30 s (except 80 degrees C, holding 20 s) and cooled to 0 to 1 degree C. At each temperature, five pressures were applied: 69, 138, 207, 276, and 345 kPa. Pressure was controlled with a needle valve at the heat exchanger exit. Both the pressure gauge and pH probe were inline at the end of the holding section. Milk pH during heating depended on CO2 concentration, temperature, and pressure. During heating of milk without added CO2, pH decreased linearly as a function of increasing temperature but was independent of pressure. In general, the pH of milk with added CO2 decreased with increasing CO2 concentration and pressure. For milk with added CO2, at a fixed CO2 concentration, the effect of pressure on pH decrease was greater at a higher temperature. At a fixed temperature, the effect of pressure on pH decrease was greater for milk with a higher CO2 concentration. Thermal death of bacteria during pasteurization of milk without added CO2 is probably due not only to temperature but also to the decrease in pH that occurs during the process. Increasing milk CO2 concentration and pressure decreases the milk pH even further during heating and may further enhance the microbial killing power of pasteurization.     

Effect of fat reduction on chemical composition, proteolysis, functionality, and yield of Mozzarella cheese

Mozzarella cheese was made from skim milk standardized with cream (unhomogenized, 40% milk fat) to achieve four different target fat percentages in the cheese (ca. 5, 10, 15, and 25%). No statistically significant differences were detected for cheese manufacturing time, stretching time, concentration of salt in the moisture phase, pH, or calcium as a percentage of the protein in the cheese between treatments. As the fat percentage was reduced, there was an increase in the moisture and protein content of the cheese. However, because the moisture did not replace the fat on an equal basis, there was a significant decrease in the moisture in the nonfat substance in the cheese as the fat percentage was reduced. This decrease in total filler volume (fat plus moisture) was associated with an increase in the hardness of the unmelted cheese. Whiteness and opacity of the unmelted cheese decreased as the fat content decreased. Pizza baking performance, meltability, and free oil release significantly decreased as the fat percentage decreased. The minimum amount of free oil release necessary to obtain proper functionality during pizza baking was between 0.22 and 2.52 g of fat/100 g of cheese. Actual cheese yield was about 30% lower for cheese containing 5% fat than for cheese with 25% fat. Maximizing fat recovery in the cheese becomes less important to maintain high cheese yield, and moisture control and the retention of solids in the water phase become more important as the fat content of the cheese is reduced.     

Development and evaluation of a processing sector model for butter manufacture using a mass balance technique at two dairy processing sites

The butter manufacturing process at two different commercial dairy processing sites in Ireland was evaluated using a mass balance approach to develop, evaluate and validate a processing sector model of the flow of milk fat from intake to final product. The mass balance was represented as a function of fat intake = fat in products + fat losses + recycled fat. Representative samples of all products, namely whole milk, cream, skim milk, butter, buttermilk and cleaning‐in‐place streams (cream silo flush, butter churn residue and sludge), were collected from two different sites. Milk fat levels and product quantities were measured to obtain the fat outputs. Total fat losses at the end of butter production ranged between 1.90% and 2.25% of the total fat input for both sites. Three different scenarios were examined to evaluate the model: S1 (Animal Breed) high genetic merit (Elite) and national average (NA) Holstein Friesian (HF) cows were evaluated, for their effect on the net value of milk; S2 (Product Portfolio) a mixed product portfolio of cheese, butter and skim milk powder (SMP) was compared to a product portfolio comprised of butter alone; and S3 (Process Efficiency) the impact of varying process losses on net values of milk and the quantities of products produced was simulated. The value per 1000 L of milk for S1 was €410.69 and €393.20 for Elite and NA cow’s milk, respectively. For S2, the butter‐only product portfolio returned €355.10, whereas the mixed‐products portfolio returned €369.60. Lastly, S3 corresponding returns for 1%, 2.2% and 5% losses was €365.90, €361.47 and €351.12, respectively.     

Concentrated emulsions as novel fat replacers in reduced-fat and low-fat Cheddar cheeses. Part 2. Large amplitude oscillatory shear behavior

Lower-fat cheeses with desirable texture can be difficult to produce. The objective of this study was to characterize the effects of concentrated emulsions as a fat replacer on the viscoelastic properties of reduced-fat (15% fat) and low-fat (6% fat) Cheddar cheeses. Concentrated emulsions were prepared by adding a fish gelatin–gum arabic mixture at pH 5.0 and 3.6 to olive oil at a water:oil ratio of 30:70 (w/w). Cheddar cheeses containing emulsions were made by adding the emulsions to skim milk after adding starter culture and before renneting and subsequent cheesemaking. Two control cheeses at each fat level were produced using either olive oil or cream. Cheeses containing emulsions showed greater nonlinearity under large amplitude oscillatory shear, and smaller critical stress and moduli values compared with controls at all storage timepoints. These results were ascribed to greater casein network discontinuity and more open spaces created by aggregated emulsion droplets.     

INFLUENCE OF TIME THICKENING ON THE WHIPPABILITY OF CREAMS

Flow properties of creams containing milk fat (Cream A), vegetable fat (Cream C), and vegetable fat plus milk fat (Cream B) were determined with a coaxial cylinder viscometer for a wide range of shear rates. All creams examined showed time thickening. The viscosity increase with shearing time was expressed by two stage equations as follows: (1) (1) where η_o and η_t are cream viscosity at zero and t shearing time, K₁ and K₂ are rate constants and C₁ and C₂ are constants. The first stage (Eq. 1) was assumed to occur in the course of primary clustering of the independent fat globules, and the second stage (Eq. 2) was assumed to occur in the course of coagulation of the fat globule clusters. Both K₁ and K₂ increased as shear rate increased.
At the same time, the whippability of each cream was determined with a household mixer to which was attached a strain gauge transducer unit for measuring consistency of the whipped creams. There was a tendency for a higher ratio of milk fat/vegetable fat in the creams to decrease the whipping time or to increase whippability of the creams.
Correlations of stability, whippability, and flow properties were examined. A cream which was high stability showed a low K₁ value, and a cream which has high whippability showed a high K₂ value. K₁ and K₂ values at a suitable shear rate will be quite helpful in the determination of the physical properties of cream.     

Heat inactivation of hepatitis A virus in dairy foods

Experiments were performed to determine the thermal resistance of hepatitis A virus (HAV) in three types of dairy products containing increased amounts of fat content (skim milk, homogenized milk; 3.5% MFG, and table cream; 18% MFG). HAV-inoculated dairy products were introduced into custom-made U-shaped microcapillary tubes that in turn were simultaneously immersed in a waterbath, using custom-made floating boats and a carrying platform. Following exposure to the desired time and temperature combinations, the contents of each of the tubes was retrieved and was tested by plaque assay to determine the reduction in virus titer. Our data indicated that < 0.5 min at 85 degrees C was sufficient to cause a 5-log reduction in HAV titer in all three dairy products, whereas at 80 degrees C, < or = 0.68 min (for skim and homogenized milk), and 1.24 min (for cream) were needed to cause a similar log reduction. Using a nonlinear two-phase negative exponential model (two-compartment model) to analyze the data, it was found that at temperatures of 65, 67, 69, 71, and 75 degrees C, significantly (P < 0.05) higher exposure times were needed to achieve a 1-log reduction in virus titer in cream, as compared to skim and homogenized milk. For example, at 71 degrees C, a significantly (P < 0.05) higher exposure time of 0.52 min (for cream) was needed as compared to < or = 0.18 min (for skim and homogenized milk) to achieve a 1-log reduction in virus titer. A similar trend of inactivation was observed at 73 and 75 degrees C where significantly (P < 0.05) higher exposure times of 0.29 to 0.36 min for cream were needed to cause a 1-log reduction in HAV in cream, as compared to < or = 0.17 min for skim and homogenized milk. This study has provided information on the heat resistance of HAV in skim milk, homogenized milk, and table cream and demonstrated that an increase in fat content appears to play a protective role and contributes to the heat stability of HAV.     

Investigation of the migration of triclabendazole residues to milk products manufactured from bovine milk,and stability therein,following lactating cow treatment

Triclabendazole (TCB) is a flukicide used in the treatment of liver fluke in cattle; however, its use is currently prohibited in lactating dairy cows. In this study, following administration of 10% Fasinex (triclabendazole, Novartis Animal Health UK Ltd., Camberley, UK) the milk of 6 animals was used to manufacture dairy products, to ascertain if TCB residues in milk migrate into dairy products. The detection limit of the ultra-high-performance liquid chromatography-tandem mass spectrometry method used was 0.67 μg/kg. The highest concentrations of TCB residue measured, within the individual cow milk yield, was 1,529 ± 244 µg/kg (n = 6), on d 2 posttreatment. Days 2 and 23 posttreatment represented high and low residue concentrations, respectively. At each of these 2 time points, the milk was pooled into 2 independent aliquots and refrigerated. Milk products, including cheese, butter, and skim milk powder were manufactured using pasteurized and unpasteurized milk from each aliquot. The results for high residue milks demonstrated that TCB residues concentrated in the cheese by a factor of 5 (5,372 vs. 918 µg/kg for cheese vs. milk) compared with the starting milk. Residue concentrations are the sum of TCB and its metabolites, expressed as keto-TCB. Residues were concentrated in the butter by a factor of 9 (9,177 vs. 1,082 μg/kg for butter vs. milk) compared with the starting milk. For milk, which was separated to skim milk and cream fractions, the residues were concentrated in the cream. Once skim milk powder was manufactured from the skim milk fraction, the residue in powder was concentrated 15-fold compared with the starting skim milk (7,252 vs. 423 µg/kg for powder vs. skim milk), despite the high temperature (185°C) required during powder manufacture. For products manufactured from milk with low residue concentrations at d 23 posttreatment, TCB residues were detected in butter, cheese, and skim milk powder, even though there was no detectable residue in the milk used to manufacture these products. Triclabendazole residues were concentrated in some milk products (despite manufacturing treatments), exceeding residue levels in the starting milk and, depending on the storage conditions, may be relatively stable over time.     

Improvement of storage stability and foaming properties of cream by addition of carrageenan and milk constituents

The increasing automation in the dairy industry and the longer guaranteed shelf life of the packed products of cream lead to a loss in the quality of liquid and whipped cream associated with the formation of irreversible plugs, too long whipping times and high degrees of liquid separation of the whipped product. In test series 0.015% carrageenan, 0.25% protein—fat as the dry matter (whey proteins with high-melting milk fat fractions) or a combination of both were added to homogenized and unhomogenized, pasteurized or ultra-high temperature treated (UHT) cream from the winter and summer feeding period (fat content: 30%). The creaming behaviour after storage at 7 or 20°C was characterized by determining the fat content in different layers of a cream package. In cream samples without additives ünstirrable layers had been formed after 2–7 weeks, in particular during the long storage times of UHT cream without cooling. A desired (i.e. low) degree of creaming of the liquid cream as well as little separation in the whipped product could be achieved for all samples only by means of a combination of carrageenan and protein—fat powder. Of the rather varying carrageenan fractions examined, a combination of similar proportions of kappa- and iota-carrageenan has proved to be particularly effective without excessively increasing viscosity.     

Polybrominated biphenyls in raw milk and processed dairy products.

Milk from four dairy herds identified by the Michigan Department of Agriculture as containing less than .3 ppm (fat basis) physiologically incorporated polybrominated biphenyls was processed individually into cream, skim milk, butter, and stirred curd cheese. Pasteurized and freeze-dried whole milk, skim milk, and cream, spray-dried whole milk and skim milk, and condensed whole milk were made also. Polybrominated biphenyls were concentrated in the high-fat products. Pasteurized skim milk, buttermilk, and whey had slightly more polybrominated biphenyls than pasteurized whole milk on a fat basis. Spray-drying reduced the polybrominated biphenyls in whole milk and skim milk while pasteurization, freeze-drying, aging of cheese, and condensation were not effective.