Production of a novel ingredient from buttermilk

The presence of material derived from the milk fat globule membrane (MFGM) makes buttermilk (the byproduct of butter making) distinct from any other dairy product. Membrane filtration of commercial buttermilk was carried out to obtain isolates rich in MFGM material. The separation of MFGM from the skim milk proteins present in commercial buttermilk was carried out by the addition of sodium citrate followed by microfiltration through a membrane of 0.1-microm nominal pore size. The sodium citrate caused the dissociation of casein micelles and allowed permeation of a large proportion of the skim-milk derived proteins through the membrane. This process successfully concentrated MFGM material in the retentate, and demonstrated that membrane filtration can be employed to produce MFGM fractions from commercial buttermilk. The utilization of MFGM isolates from buttermilk is of increasing importance in light of recent studies suggesting the role of phospholipids in many health-related functions: buttermilk is an untapped resource of these functional components.     

Effect of buttermilk made from creams with different heat treatment histories on properties of rennet gels and model cheeses

Although many studies have reported negative effects on cheese properties resulting from the use of buttermilk in cheese milk, the cause of these effects has not been determined. In this study, buttermilk was manufactured from raw cream and pasteurized cream, as well as from a cream derived from pasteurized whole milk. Skim milks with the same heat treatments were also manufactured to be used as controls. Compositional analysis of the buttermilks revealed a pH 4.6-insoluble protein content approximately 10% lower than that of the skim milk counterparts. Milk fat globule membrane (MFGM) proteins remained soluble at pH 4.6 in raw cream buttermilk; however, when heat was applied to cream or whole milk before butter making, MFGM proteins precipitated with the caseins. Rennet gel characterization showed that MFGM material in the buttermilks decreased the firmness and increased the set-to-cut time of rennet gels, but this effect was amplified when pasteurized cream buttermilk was added to cheese milk. The microstructure of gels was studied, and it was observed that gel appearance was very different when pasteurized cream buttermilk was used, as opposed to raw cream buttermilk. Model cheeses manufactured with buttermilks tended to have a higher moisture content than cheeses made with skim milks, explaining the higher yields obtained with buttermilk. Superior retention of MFGM particles was observed in model cheeses made from pasteurized cream buttermilk compared with raw cream buttermilk. The results from this study show that pasteurization of cream and of whole milk modifies the surface of MFGM particles, and this may explain why buttermilk has poor coagulation properties and therefore yields rennet gels with texture defects.     

Isolation of milk fat globule membrane (MFGM) material by coagulation and diafiltration of buttermilk

Due to the functional potential of milk fat globule membrane (MFGM), its isolation from buttermilk is receiving increasing attention by the food industry. However, extraction of MFGM proteins from buttermilk is challenging because of the high levels of serum proteins. In this study, a two-step approach was applied to obtain a MFGM isolate. First, native casein micelles from buttermilk were removed by rennet-induced coagulation. Next, the buttermilk whey obtained was filtered to remove the residual whey proteins. Purified MFGM isolate was collected after six diafiltration steps. The yield of MFGM proteins in the isolates was determined using sodium dodecylsulphate-polyacrylamide gel electrophoresis. In the MFGM isolates, 70% of peripheral membrane proteins were obtained, which is much more effective in comparison with recent isolation methods like cream washing or filtration of buttermilk. Further investigations on casein coagulation conditions of buttermilk may reduce losses, especially of integral MFGM proteins during renneting.     

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.     

Use of ultrafiltration and supercritical fluid extraction to obtain a whey buttermilk powder enriched in milk fat globule membrane phospholipids

Whey buttermilk, a by-product from whey cream processing to butter, is rich in milk fat globule membrane (MFGM) constituents, which have technological and potential health properties. The objective of this work was to produce a dairy ingredient enriched in MFGM material, especially phospholipids, from whey buttermilk. Whey buttermilk was concentrated by ultrafiltration (10×) and subsequently diafiltered (5×) (10 kDa molecular mass cutoff membrane) at 25 °C and the final retentate was spray-dried. The whey buttermilk powder was submitted to supercritical extraction (350 bar, 50 °C) using carbon dioxide. The membrane filtration removed most of the lactose and ash from the whey buttermilk, and the supercritical extraction extracted exclusively non-polar lipids. The final powder contained 73% protein and 21% lipids, of which 61% were phospholipids. This ingredient, a phospholipids-rich dairy powder, could be used as an emulsifier in different food systems.     

Butter making from caprine creams: effect of washing treatment on phospholipids and milk fat globule membrane proteins distribution

A washing treatment was applied to caprine cream before churning in order to improve phospholipids and MFGM protein purification from buttermilk and butter serum. Cream obtained from a first separation was diluted with water and separated a second time using pilot plant equipment. Regular and washed creams were churned to produce buttermilk and butter, from which butter serum was extracted. The washing treatment allowed a significant decrease of the casein content. As a result, the phospholipids-to-protein ratios in washed buttermilk and butter serum were markedly increased by 2.1 and 1.7-folds respectively, which represents an advantage for the production of phospholipids concentrates. However, when compared with bovine cream, lower phospholipids-to-protein ratios were observed when the washing treatment was applied to caprine cream. A higher concentration of MFGM protein and a lower retention of phospholipids during washing treatment are responsible for the lower phospholipids-to-protein ratios in buttermilk and butter serum obtained from caprine cream. The phospholipids distribution in the butter making process was similar to the one obtained from bovine regular and washed cream. Phospholipids were preferentially concentrated in the butter serum rather than the buttermilk fraction. This simple approach permitted the production of caprine and bovine butter sera extracts containing up to 180 and 240 g phospholipids/kg sera, respectively, on a dry basis.     

Casein precipitation by acid and rennet coagulation of buttermilk: Impact of pH and temperature on the isolation of milk fat globule membrane proteins

Milk fat globule membrane (MFGM) proteins make up only 2–3% of the total protein content in buttermilk. Prior isolation of buttermilk MFGM material is therefore required for further investigation of its functional properties and application in food systems. Rennet induced coagulation has been applied to remove caseins, but 30–70% of MFGM proteins are entrapped in the casein curd under classical cheese making conditions. Therefore, factors influencing the rennet as well as acid induced coagulation of buttermilk with regard to a reduction of MFGM protein losses into the casein curd, i.e., pH, temperature and pre-heat treatment of buttermilk, were examined. Complete casein removal from buttermilk was reached using both coagulation methods, whereas retention of MFGM proteins in the serum phase was higher during renneting. Rennet induced coagulation at higher pH and lower temperatures resulted in weaker gel structures, which increased the yield of MFGM proteins in the buttermilk whey.     

Effect of processing on the composition and microstructure of buttermilk and its milk fat globule membranes

The effect of cream pasteurization on the composition and microstructure of buttermilk after pasteurization, evaporation and spray-drying was studied. The composition of milk fat globule membrane (MFGM) isolated from buttermilk samples was also characterized. Pasteurization of cream resulted in higher lipid recovery in the buttermilk. Spray-drying of buttermilk had a significant effect on phospholipid content and composition. After spray-drying, the phospholipid content decreased by 38.2% and 40.6%, respectively in buttermilk from raw or pasteurized cream when compared with initial buttermilks. Pasteurization of cream resulted in the highest increase in whey protein recovery in MFGM isolates compared with all other processing steps applied on buttermilk. A reduction in phospholipid content was also observed in MFGM isolates following spray-drying. Transmission electron microscopy of the microstructure of buttermilks revealed extremely heterogeneous microstructures but failed to reveal any effect of the treatments.     

Effect of heating whey proteins in the presence of milk fat globule membrane extract or phospholipids from buttermilk

The objective of this study was to determine the contribution of phospholipids from buttermilk as a nucleus in the heat-induced aggregation of whey proteins. Solutions of whey proteins (5%, w/v) were adjusted to pH 4.6 or 6.8 and then heated at 65 or 80 °C for 25 min with or without 1% (w/v) of milk fat globule membrane (MFGM) extract or phospholipid powder. The aggregation mechanisms were characterised using analysis with Ellman's reagent, one-dimensional gel electrophoresis, thin-layer chromatography, and three-dimensional confocal laser-scanning microscopy. Three-dimensional images showed protein/phospholipid interactions in the presence of MFGM extract or phospholipids, and thin-layer chromatography plates showed no trace of free phospholipids after 20 min at pH 4.6. Overall, the results demonstrate that phospholipids from buttermilk were involved in the formation of protein aggregates through the MFGM fragments at a low temperature, whereas phospholipids could interact directly with the proteins at a higher temperature (80 °C).     

Concentration of polar MFGM lipids from buttermilk by microfiltration and supercritical fluid extraction

Buttermilk contains the milk fat globule membrane (MFGM), a material that possesses many complex lipids that function as nutritionally valuable molecules. Milk-derived sphingolipids and phospholipids affect numerous cell functions, including regulating growth and development, molecular transport systems, stress responses, cross membrane trafficking, and absorption processes. We developed a two-step method to produce buttermilk derivative ingredients containing increased concentrations of the polar MFGM lipids by microfiltration and supercritical fluid extraction (SFE). These processes offer environmentally benign alternatives to conventional lipid fractionation methods that rely on toxic solvents. Firstly, using a ceramic tubular membrane with 0.8-micron pore size, we evaluated the cross flow microfiltration system that maximally concentrated the polar MFGM lipids using a 2n factorial design; the experimental factors were buttermilk source (fresh, or reconstituted from powder) and temperature (50 degrees C, and 4 degrees C). Secondly, a SFE process using supercritical carbon dioxide removed exclusively nonpolar lipid material from the microfiltered buttermilk product. Lipid analysis showed that after SFE, the product contained a significantly reduced concentration of nonpolar lipids, and a significantly increased concentration of polar lipids derived from the MFGM. Particle size analysis revealed an impact of SFE on the product structure. The efficiency of the SFE system using the microfiltration-processed powder was compared much more favorably to using buttermilk powder.     

Filtration of milk fat globule membrane fragments from acid buttermilk cheese whey

The proteins and polar lipids present in milk fat globule membrane (MFGM) fragments are gaining attention for their technological and nutritional properties. These MFGM fragments are preferentially enriched in side streams of the dairy industry, like butter serum, buttermilk, and whey. The objective of this study was to recover MFGM fragments from whey by tangential filtration techniques. Acid buttermilk cheese whey was chosen as a source for purification by tangential membrane filtration because it is relatively rich in MFGM-fragments and because casein micelles are absent. Polyethersulfone and cellulose acetate membranes of different pore sizes were evaluated on polar lipid and MFGM-protein retention upon filtration at 40°C. All fractions were analyzed for dry matter, ash, lipids, proteins, reducing sugars, polar lipid content by HPLC, and for the presence of MFGM proteins by sodium dodecyl sulfate-PAGE. A fouling coefficient was calculated. It was found that a thermocalcic aggregation whey pretreatment was very effective in the clarification of the whey, but resulted in low permeate fluxes and high retention of ash and whey proteins. By means of an experimental design, the influence of pH and temperature on the fouling and the retention of polar lipids (and thus MFGM fragments), proteins, and total lipids upon microfiltration with 0.15 μM cellulose acetate membrane was investigated. All models were highly significant, and no outliers were observed. By increasing the pH from 4.6 to 7.5, polar lipid retention at 50°C increased from 64 to 98%, whereas fouling of the filtration membrane was minimized. A 3-step diafiltration of acid whey under these conditions resulted in a polar lipid concentration of 6.79 g/100 g of dry matter. As such, this study shows that tangential filtration techniques are suited for the purification of MFGM fragments.     

Effect of temperature and pore size on the fractionation of fresh and reconstituted buttermilk by microfiltration

The objective of this research was to evaluate the effect of temperature (7, 25, and 50 degrees C) and pore size (0.1, 0.8, and 1.4 micro m) on the separation of proteins and lipids (neutral lipids and phospholipids) during microfiltration (MF) of fresh or reconstituted buttermilk. Buttermilk was subjected to MF using a pilot-scale unit mounted with ceramic membranes. The MF runs were carried out in a uniform transmembrane pressure (UTP) mode. Changes in processing temperature had no significant impact on protein transmission, whereas increasing temperature reduced both lipid and phospholipid transmission. A maximum concentration factor (CF) for lipids was reached at 25 degrees C, as protein CF remained essentially unaffected by temperature. The use of the smaller pore size (0.1 microm) resulted in low lipid (10%) and protein (approximately 20%) transmission. Larger pore sizes (0.8 and 1.4 microm) resulted in higher levels of protein, lipid, and phospholipid transmission (>50%), but gave high permeation fluxes. Transmission of both proteins and lipids was markedly different when using fresh buttermilk as opposed to reconstituted buttermilk. This study showed that MF temperature, pore size, and buttermilk type influence fractionation but that MF alone cannot achieve optimal separation of lipids and proteins for the production of novel ingredients from buttermilk.     

Emulsifying properties of fractions prepared from commercial buttermilk by microfiltration

A novel method for the separation of milk-fat globule membrane (MFGM) isolate by microfiltration in the presence of citrate was applied to prepare a fraction to be used to stabilize oil-in-water emulsions. The emulsifying properties of this fraction, containing high amounts of MFGM, were compared with a buttermilk concentrate (BMC) prepared in a similar manner but still containing the original ratio of proteins (caseins, whey proteins, and MFGM). The objective of this work was to determine if the isolation procedure would result in an ingredient with different functionality when compared with BMC. These fractions were incorporated into oil-in-water emulsions at various isolate and oil concentrations. At low concentrations of isolate, MFGM emulsions showed better creaming stability and smaller oil droplet size distribution than whole buttermilk concentrate samples. The difference in stability was attributed to the compositional difference between the 2 ingredients prepared. A selective concentration of MFGM in buttermilk by microfiltration has the potential for the development of ingredients that differ substantially from the ingredients deriving from milk or whey.     

Effects of buttermilk powders on emulsification properties and acid tolerance of cream

Emulsifying properties and acid tolerance are 2 of the most important characteristics of cream. The effects of the buttermilk component, especially its phospholipids, on the emulsifying properties and acid tolerance of cream were investigated in this study. Two buttermilks with differing phospholipid contents and skimmed milk were used to evaluate the effects of phospholipids on the aforementioned parameters. The mean diameter of fat globules and the cream viscosity were used as indicators of emulsifying properties. Acid tolerance was evaluated by studying the effect of citric acid on the maximum viscosity of cream. This was tested by adding 400 μL of 10% (w/w) citric acid solution to cream every minute and simultaneously measuring pH and viscosity. In 45% and 40% fat cream systems, buttermilk, and especially that with higher phospholipid content, improved the emulsifying properties and acid tolerance of the cream. The components of buttermilk could alter the properties of the surface of fat globules, thereby altering the emulsification properties of the cream. However, neither of the tested buttermilks affected the emulsifying properties and acid tolerance of lower-fat (35% and 30%) cream systems. Emulsifying components exist in proportionately larger amounts in lower-fat creams, which could render the emulsifying properties resistant to change. The number of fat globules may also influence acid-induced changes in viscosity. The addition of phospholipids or lysophospholipids did not improve the acid tolerance of creams, a finding that may be attributable to the formation of complexes of phospholipids and protein. PRACTICAL APPLICATION: The findings presented herein demonstrate the ability to improve the acid tolerance of cream using materials derived from milk. Implementing these findings appropriately may result in a high-quality cooking cream.     

A microfiltration process to maximize removal of serum proteins from skim milk before cheese making

Microfiltration (MF) is a membrane process that can separate casein micelles from milk serum proteins (SP), mainly beta-lactoglobulin and alpha-lactalbumin. Our objective was to develop a multistage MF process to remove a high percentage of SP from skim milk while producing a low concentration factor retentate from microfiltration (RMF) with concentrations of soluble minerals, nonprotein nitrogen (NPN), and lactose similar to the original skim milk. The RMF could be blended with cream to standardize milk for traditional Cheddar cheese making. Permeate from ultrafiltration (PUF) obtained from the ultrafiltration (UF) of permeate from MF (PMF) of skim milk was successfully used as a diafiltrant to remove SP from skim milk before cheese making, while maintaining the concentration of lactose, NPN, and nonmicellar calcium. About 95% of the SP originally in skim milk was removed by combining one 3 x MF stage and two 3 x PUF diafiltration stages. The final 3 x RMF can be diluted with PUF to the desired concentration of casein for traditional cheese making. The PMF from the skim milk was concentrated in a UF system to yield an SP concentrate with protein content similar to a whey protein concentrate, but without residuals from cheese making (i.e., rennet, culture, color, and lactic acid) that can produce undesirable functional and sensory characteristics in whey products. Additional processing steps to this 3-stage MF process for SP removal are discussed to produce an MF skim retentate for a continuous cottage cheese manufacturing process.     

Changes in structure of the bovine milk fat globule membrane on heating whole milk.

The effects of heat-induced interactions between milk fat globule membrane components and skim milk proteins in whole milk on the structure of the membrane were examined by isopycnic sucrose density gradient centrifugation and by using Triton X-100 as a membrane probe. Skim milk components were incorporated into all the lipoprotein fractions separated by density gradient centrifugation. High density complexes, higher in density than those found in the natural milk fat globule membrane, were formed during the heat treatment. Losses of natural membrane polypeptides from the medium and low density lipoproteins were observed on heating. Heating whole milk also altered the rate of release of membrane components by detergent, with decreases in protein released and an increase in phospholipid constituents released. Studies on washed cream indicated that some of the changes in the membrane on heating whole milk occurred due to the heat treatment alone, independent of the interactions with skim milk proteins.     

Impact of cream washing on fat globules and milk fat globule membrane proteins

Milk proteins, contained within the aqueous phase surrounding fat globules, should be removed before analysis of the composition of the native milk fat globule membrane (MFGM). The effect of the conditions applied during washing of cream on MFGM integrity has not been fully studied, and factors potentially effecting a modification of MFGM structure have not been systematically assessed so far. In this study, a cream separator was used to investigate the impact of cream washing on milk fat globule stability and the corresponding loss of MFGM proteins. Flow velocity, fat content, and type of washing solution were varied. Particle size measurements and protein analyses were carried out after each washing step to determine fat globule coalescence, removal of skim milk proteins, and efficiency of MFGM isolation. Significant differences in fat globule stability and protein amount in the MFGM isolates were measured using different washing conditions.     

Changes in the surface protein of the fat globules during ultra-high pressure homogenisation and conventional treatments of milk

Disruption of fat globules upon homogenisation provokes a reduction of their size and a concomitant increase in their specific surface area. In order to overcome this phenomenon, the milk fat globule membrane (MFGM) adsorbs non-native MFGM proteins. The aim of the present study was to examine the effects of UHPH conditions (temperature and pressure) on the milk fat globule and the surface proteins by comparison with conventional treatments applied in the dairy industry. Transmission electron microscopy and SDS-PAGE revealed major differences. In UHPH-treated milk, casein micelles were found to be adsorbed on the MFGM in a lesser extent than in conventional homogenisation–pasteurisation. However, greater adsorption of directly bonded casein molecules, released by UHPH through the partial disruption of casein micelles, was observed especially at high UHPH pressures. Adsorption of whey proteins on the MFGM of conventionally homogenised–pasteurised milk was mainly through intermolecular disulfide bonds with MFGM material, whereas in UHPH-treated milk, disulfide bonding with both indirectly and directly adsorbed caseins was also involved.     

Phospholipid enrichment in sweet and whey cream buttermilk powders using supercritical fluid extraction

Milk fat globule membrane contains many complex lipids implicated in an assortment of biological processes. Microfiltration coupled with supercritical fluid extraction (SFE) has been shown to provide a method of concentrating these nutritionally valuable lipids into a novel ingredient. In the dairy industry there are several by-products that are rich in phospholipids (PL) such as buttermilk, whey, and whey cream. However, PL are present at low concentrations. To enrich PL in buttermilk powders, regular buttermilk and whey buttermilk (by-product of whey cream after making butter) were microfiltered and then treated with SFE after drying. The total fat, namely nonpolar lipids, in the powders was reduced by 38 to 55%, and phospholipids were concentrated by a factor of 5-fold. Characterization of the PL demonstrated specific molecular fatty amide combinations on the sphingosine (18:1) backbone of sphingomyelin with the greatest proportion being saturated; the most common were 16:0, 20:0, 21:0, 22:0, 23:0, and 24:0. Two unsaturated fatty amide chains, 23:1 and 24:1, were shown to be elevated in a whey cream buttermilk sample compared with the others. However, most unsaturated species were not as abundant.     

Buttermilk Properties in Emulsions with Soybean Oil as Affected by Fat Globule Membrane-Derived Proteins

The potential utilization of buttermilk from an industrial source was studied in this research, focusing primarily on its composition and use as ingredient in oil-in-water emulsions. Buttermilk contained not only large amounts of caseins and whey proteins, but also material derived from the natural milk fat globule membrane (MFGM). Emulsions made with soybean oil (10% w/w) and buttermilk were stable with a low concentration (about 1% w/w) of buttermilk solids. MFGM-proteins and skim milk proteins did not seem to compete for adsorption at the emulsion interface. The protein adsorbed at the interface was present in an aggregated form and gave a maximum surface coverage of about 8 mg/m².