Manufacturing - Butter/Milkfat - 2000
Modification of Milkfat to Improve Manufacturing Properties and Nutritional Quality - Edward DePeters, UC Davis
Effect of DNA Polymorphism of Delta 9 (D9) Desaturase on the Fatty Acid and CLA Content of Milkfat - Edward DePeters, UC Davis
Modification of Cream Functionality by a Novel Adsorption Process - Rafael Jiménez-Flores, Cal Poly San Luis Obispo
Milk as a Nutritional Delivery System for Fat-Soluble Nutrients - Bruce German, UC Davis
Modification of the Composition of Milkfat in Dairy Cows - Juan F. Medrano, UC Davis
The Evaluation of the Efficacy of Increasing the Monounsaturated to Saturated Milkfat Ratio via Expressing a Steroyl-CoA Desaturase Transgene - James D. Murray, UC Davis
Composite Whey Protein Gels Containing Fractionated Milkfat: An Application for Fractionated Milkfat - Moshe Rosenberg, UC Davis
Modification of Milkfat to Improve Manufacturing Properties and Nutritional Quality
Edward DePeters, UC Davis
The objective of this project is to modify the fatty acid composition and triglyceride structure of milkfat in a fashion that will improve the nutritional value and manufacturing properties of milkfat through either diet or genetics of the dairy cow. Nutrition and genetic studies were completed and data analyses continue.
Earlier work demonstrated that the diet of the cow can be altered to increase the monounsaturated fatty acid composition of milkfat and later triglyceride structure. Improving the nutritional value of milkfat places dairy products in a more favorable context to consumers. Altering the fatty acid composition of milkfat has improved the spreading characteristics of butter. Breed (genetics) was also found to affect the fatty acid composition of milkfat. Breed differences in oleic acid content were found. Milkfat of Jersey cows was lowest in C18:1 in milkfat while Brown Swiss cows had the highest and Holstein cows were in the mid range. These results could be related in part to the stearoyl CoA desaturase enzyme system that converts C18:0 to C18:1. Identifying animals with high activity of the stearoyl CoA desaturase gene will allow breeding programs on dairy farms that result in increased C18:1 in milkfat. Likewise, improving our knowledge of the factors controlling the activity of the stearoyl CoA desaturase enzymes will result in new management programs to enhance the C18:1 content of milkfat. Improving the monounsaturated fatty acid (C18:1) content of milkfat will benefit the sale of dairy products containing milkfat. It may also be possible to reduce other saturated fatty acids in milkfat, including palmitic (C16:0) and myristic (C14:0) acids, which are fatty acids associated with human health.
Altering triglyceride structure through nutrition of the cow has implications for the use of milkfat in various manufactured products. Currently, postharvest techniques of triglyceride fractionation are used to modify the physiochemical properties of milkfat. However, if a portion of the necessary modifications can be accomplished by preharvest techniques, for example nutrition of the cow, more dramatic and economic changes can be accomplished in conjunction with postharvest techniques.
Feeding an increasing amount of fat in the form of yellow grease to lactating cows of the Holstein, Jersey and Brown Swiss breed increased the C18:1 and C18:2 cis 9 trans 11 (CLA) composition of milkfat. Milkfat from Jersey cows was lower in C18:1 and CLA than milkfat from both Holstein and Brown Swiss cows. This difference is proposed to be due to differences in the stearoyl CoA desaturase activity in the mammary gland. In subsequent research, feeding highly saturated fat to lactating Holstein cows increased the C18:1 content of milkfat, but not the CLA content. Feeding an unsaturated fat source to lactating Holstein cows increased both the C18:1 and CLA content of milkfat. These changes alter the nutritional value and manufacturing properties of the milkfat. It will be possible in the future to identify cows genetically superior for producing milkfat higher in C18:1 content. Breeding and nutrition programs will be established to produce milk containing milkfat of desired fatty acid composition.
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Effect of DNA Polymorphism of Delta 9 (D9) Desaturase on the Fatty Acid and CLA Content of Milkfat
Edward DePeters, UC Davis
The objective of the research is to determine if the concentration of monounsaturated fatty acid and CLA (conjugated linoleic acid) in the milkfat of lactating Holstein dairy cows differs with the DNA polymorphism for the D9 desaturase (stearoyl CoA desaturase) gene. Increasing the monounsaturated fatty acid (oleic acid) and decreasing the saturated fatty acid composition improves the nutritional value of milkfat for humans and alters the manufacturing properties of the milkfat. CLA is a group of fatty acids that were shown to possess anticarcinogenic properties in rodents and are currently being investigated for their benefit in humans. CLA isomers are considered nutraceuticals in food because of their potential benefits to human health. Increasing the monounsaturated fatty acid, and CLA fatty acids in milkfat improves the image of milkfat and will add value to dairy products.
To determine the effect of fatty acid composition of the diet on the CLA content of milkfat, special diets were fed to cows identified for polymorphism for the D9 desaturase (stearoyl CoA desaturase) gene. In the first study a highly saturated source of dietary fat was fed to the lactating dairy cows over a period of four months. If the rumen microbes are contributing to the CLA content of milkfat through the hydrogenation of unsaturated fatty acids, the CLA content of milkfat should not be affected by the feeding of a highly saturated fat source. Neither the amount of fat fed nor the D9 desaturase genotype of the cow affected the CLA content of milkfat. The CLA content of milkfat averaged 3.2, 2.8 and 3.2 mg/g of fat for AA, AB and BB genotypes. The trans 11 isomer of C18:1 was also not affected by diet or genotype. The trans 11 C18:1 content of milkfat was 2.4, 2.4 and 2.3 mg/g of fat for AA, AB and BB. We proposed that these would be the responses to feeding highly saturated fat to lactating cows differing in the D9 desaturase genotype.
In the second study, the same cows from the first study were fed a diet containing a rich source of unsaturated fatty acids. Soybean oil was used because of its high C18:2 (linoleic acid) content. Biohydrogenation of unsaturated fatty acids in the rumen may contribute CLA, which can be incorporated into milkfat. Additionally, biohydro-genation of C18:2 can yield trans 11 C18:1. At the mammary gland, this trans fatty acid may be desaturated to CLA by the D9 desaturase enzyme. The CLA content of milkfat increased with the addition of soybean oil to the diet. However, the CLA content of milkfat was not different for D9 desaturase genotype.
In a final study, a group of 27 lactating Holstein cows was fed the same diet, but cows were blocked into groups based on D9 desaturase genotype as well as milk production and parity. Changes in fatty acid composition for genotype were small. We are currently investigating whether or not polymorphism exists in the promoter region of the gene that would allow us to distinguish differences in fatty acid composition of cows related to the D9 desaturase gene.
The findings have potential practical implications. The fatty acid composition of the dietary fat affects the fatty acid and CLA content of milkfat. Therefore, it is possible for dairy producers to feed diets that enhance the monounsaturated and CLA content of milkfat. Dairy products containing milkfat will have higher CLA content, which will improve the nutritional value of milkfat for human consumption. Ruminant products provide good sources of CLA while plant oils are poor sources of CLA. In addition, the CLA isomers in ruminant products source as milk and meat fats are the biologically active isomer.
Research on modifying the CLA content of milkfat is continuing. A USDA grant was obtained by the University of Nevada at Reno and the University of California, Davis, to study the effects of nutrition on the CLA content of meat and milk and the role of CLA in human health. The funding support of the grant summarized in this report by the California Dairy Research Foundation positioned researchers at UC Davis to obtain USDA funding. This new project will provide further information for the dairy industry.
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Modification of Cream Functionality by a Novel Adsorption Process
Rafael Jiménez-Flores, Cal Poly San Luis Obispo
The objectives of this project include
- Developing a novel process for use in industry to improve buttermilk quality
- Obtaining specific knowledge on the effect of three commercially available biosilicates on buttermilk
- Understanding the scientific principles that control this process.
Within the United States there exists an unrealized potential for greater use of buttermilk and buttermilk powder. Buttermilk has traditionally been used as a cheap source of solids in ice cream, bakery products or as animal feed. Perhaps the greatest deterrent to its expanded use stems from issues in quality variation, which lead to variability in functionality.
We used biosilicates to modify the functional properties and quality of buttermilk. Biosilicate, also called diatomaceous earth, is a fine powder with particle sizes ranging from 5 to 50 mm in diameter. It is composed of almost pure silica. Currently, biosilicate is used in the food industry mainly as filtration aids for removal of particulates from juices, beer and wines. Biosilicate can be used in its natural state or synthetically modified to enhance desired characteristics.
We worked with three commercially available synthetic biosilicates (calcium silicate, magnesium silicate and Hyflo). Calcium silicate and magnesium silicate are produced by the hydro-thermal reaction of natural biosilicate with hydrated lime or hydrated magnesia. Hyflo is a fused biosilicate designed to be a monodispersed substance.
Buttermilk was treated at both benchtop and pilot plant levels. To gain an understanding of the functional properties of treated buttermilk, emulsions of 10 percent fat were made by homogenization of the treated buttermilk with a fat source. Buttermilk was treated with three types of biosilicates to understand the role of different types of biosilicates in this process. Additionally, three fat sources were used—butter, soybean oil and vegetable shortening—to determine if lipid type has an affect on the buttermilk’s functionality. This provides information useful to the incorporation of treated buttermilk in to a wide variety of food products. The buttermilk, recovered biosilicates and emulsions were subjected to a battery of tests to help determine what changes occurred during the process. The protein and lipid composition of the buttermilk and recovered biosilicates were measured to examine changes that might have occurred. The emulsions were characterized by evaluation of viscosity, foaming, creaming rate, particle size, protein composition and protein load of the fat globule membrane. Analysis of the treated buttermilk showed that little change occurred from the process (i.e., from a nutritional standpoint, the buttermilk remains unchanged by the process). However, when the treated buttermilk was used to make emulsions, many significant changes in functionality were found. For example, treatment with various types of biosilicates resulted in changes in viscosity, foam capacity and foam stability. Examination of the recovered biosilicates showed that the biosilicates did in fact adsorb different proteins and glycoproteins, which explains some of the differences seen in the emulsions. To gain a deeper understanding of the emulsions formed, we studied the fat globule membrane of the newly formed emulsion. SDS-PAGE revealed differences in the proteins present on the membranes of the various emulsion. Protein load of the fat globules was calculated revealing large variation in the amount of protein that adsorbed into the newly formed membrane. The general findings show that minor changes in buttermilk lead to significant changes in proteins on membrane surface, which in turn dramatically affect functionality of buttermilk
The biosilicate’s ability to adsorb certain components from buttermilk and butteroil was also studied. Specifically, the absorptive capacity of the three types of biosilicates for free fatty acids from the an aqueous model system and from butter was evaluated. Gas chromatography was used to quantitate the levels of butyric acid both before and after treatment with biosilicates. These results were compared with sensory evaluation information. The biosilicates examined have the ability to decrease free fatty acid levels in dairy systems both with and without the presence of fat.Of the biosilicates compared, magnesium silicate was found to be the most effective in a fat-containing system, while calcium silicate is believed to be the most effective in a non-fat system. Applied to dairy products such as milk, cream, buttermilk or butter oil, this process has the potential to become a commercial method for standardizing and improving quality by reducing free fatty acids.
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Milk as a Nutritional Delivery System for Fat-Soluble Nutrients
J. Bruce German, UC Davis
Milk and milkfat have been observed to be potentially excellent vehicles for vitamin E delivery, but it is not clear why and furthermore, it is not clear if milk contains sufficient vitamin E for optimal nutrition. This summary reports results of experiments addressing the following objectives:
- To develop methods to determine tocopherol isomers in blood, lipoproteins and dairy products
- To establish tocopherol levels in various dairy products and reduced fat dairy products relative to established requirements
- To determine the role of milkfat in the absorption of milk fat and fat soluble nutrients.
To date, methods have been established for routine analysis of tocopherol isomers with high sensitivity to enable measurements in very small quantities of isolated blood lipoproteins and dairy products.
Dairy products were analyzed and found to contain primarily the vitamin E isomer alpha tocopherol in levels in direct proportion to total fat and cholesterol. Hence the removal of fat to produce low-fat dairy products removes proportionately the tocopherols as well.
Dietary experiments were conducted with hamsters to determine the effect of fat on absorption of different tocopherol isomers and carotenoids into blood lipoproteins.
Tocopherols and carotenoids were well absorbed from both dietary fats with all of the fat-soluble nutrients appearing in the lipoproteins of the animals following their ingestion. However, the milkfat-fed animals compared to the corn-oil fed animals exhibited greater proportions of alpha tocopherol relative to gamma tocopherol even when both tocopherols were fed at the same level in the diets.
Milk is a source of vitamin E in the diet primarily because the active vitamin E isomer alpha tocopherol is the major isomer in milkfat. Although milk does not contain high quantities of vitamin E, the presence of milkfat encourages the absorption of this and other fat-soluble nutrients. With the recognition that few foods are able to provide sufficient alpha tocopherol to meet recently revised dietary guidelines and the ability of milk to carry and deliver vitamin E successfully to tissues, the dairy industry should consider supplementing dairy products with alpha tocopherol to become the logical dietary carrier of this essential vitamin.
Alpha tocopherol is well absorbed and delivered to circulating lipoproteins from a milkfat matrix. Removal of milkfat from dairy products removes the vitamin E as well as the fat. Therefore, the dairy industry should consider supplementing its products with alpha tocopherol and positioning itself as the dietary food of choice for this nutrient.
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Modification of the Composition of Milkfat in Dairy Cows
Juan F. Medrano, UC Davis
The majority of the fat in milk (approximately 98 percent) is in the form of triglycerides. Triglycerides have a 3-carbon (C) backbone with fatty acids (FA) attached to each one of the carbon positions. The FA structure of the trygliceride determines the functionality (plasticity and spreadability) for manufacturing processes, and the nutritional health properties of milkfat. The objectives of this project are to
- Clone and sequence important genes controlling the fatty acid composition of milk in the bovine mammary gland
- Identify polymorphisms (genetic variants) between and within dairy cattle breeds in the coding and regulatory regions of the above genes
- Evaluate associations between these polymorphisms and differences in the fatty acid composition of cow’s milk to use them as markers for genetic selection
Our work has been directed toward identifying and characterizing large genomic BAC insert clones containing the full length desaturase gene for the purpose of sequencing the promoter and flanking regions of the gene. We have sequenced the first 900 base pairs of the promoter in nine Holstein, Jersey and Brown Swiss cows with the objective of identifying potential polymorphism that may be associated with differences in gene expression. We know from our fatty acid composition studies that significant differences exist between breeds in the milk composition of stearic and oleic acid, and conjugated linoleic acid. We are working to determine if these differences can be associated with structural differences of the stearoyl-CoA desaturase gene. In addition, we have collaborated with Dale Bauman at Cornell University to evaluate the effect of the stearoyl-CoA desaturase polymorphisms in experimental cows in nutritional interventions to alter fat composition.
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The Evaluation of the Efficacy of Increasing the Monounsaturated to Saturated Milkfat Ratio via Expressing a Steroyl-CoA Desaturase Transgene
James D. Murray, UC Davis
The objectives for this project are to
- Design and develop a mouse model expressing the human stearoyl-CoA desaturase cDNA in the mammary gland
- Characterize stearoyl-CoA desaturase expression in the mammary gland at the mRNA and protein levels
- Characterize fatty acid composition of mouse milk and compare it to stearoyl-CoA desaturase transgenic mouse milk.
This research is designed to use transgenic mice as a model to study the effect of expressing a fat synthesis gene in the mammary gland on the fatty acid composition of the resulting milk. We believe we can direct increased expression of a gene in the mammary gland and that expression of this gene will alter the fatty acid composition of milk to yield a milk containing lower amounts of saturated (considered bad fat for cardiovascular health) and higher amounts of monounsaturated, or good, fatty acids. A transgenic mouse model gives us an opportunity to study the mechanisms of function of the transgene in the mammary gland and to model the positive health benefits of altered fatty acid composition of cows milk if extrapolated to transgenic dairy animals.
This project has three sequential aims. First, we need to make a gene construct to express the gene in milk and produce transgenic mice carrying this construct. Once we have mice carrying the gene, we need to characterize desaturase expression in the mammary gland at the RNA and protein levels. Finally, once we have lines of transgenic mice to predict the level of expression in the human gene, we need to characterize the fatty acid composition of mouse milk and compare it to transgenic mouse milk. If we can show that the composition of fatty acids is significantly altered, then we could expect positive health benefits for humans if the same change was introduced into the mammary gland of a dairy cow.
Given the expense of producing transgenic cows, it is logical to carry out the initial work in mice to demonstrate that we can significantly alter fat composition before undertaking the production of transgenic ruminants. To that end, two gene constructs were constructed and a total of 19 transgenic founder animals were produced. From these animals, 13 transgenic mouse lines have been established—one based on the goat b-casein promoter construct and the remainder on the cattle b-lactoglobulin promoter construct.
Saturated fatty acids in the diet raise serum cholesterol concentrations and one-third of the saturated fatty acid in American diets comes from the consumption of dairy products. Milk has short-chain and saturated fatty acids. Many health recommendations have been made to reduce human consumption of saturated fatty acids. Thus, milk with an altered fatty acid composition would be of great benefit and value. It is clear that alterations in saturated content can be obtained nutritionally and that human consumption of such altered products can significantly alter cholesterol levels. The "ideal" nutritional milkfat, based on dietary recommendations, consist of approximately 25 percent saturated fatty acids, 75 percent monounsaturated fatty acids and 5 percent polyunsaturated fatty acids. Preliminary data collected on milk from four of the transgenic mouse lines suggests that the expression of the desaturase transgene in the mammary gland has resulted in significant alterations in the amount of one or more of the major saturated fatty acids (14:0, 16:0, and 18:0) in each line, as well as the amount of the derived monounsaturated fatty acid. Based on the preliminary data, the potential appears to exist, assuming appropriate levels of transgene expression are obtained, for significantly altering milk fatty acid composition
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Composite Whey Protein Gels Containing Fractionated Milkfat: An Application for Fractionated Milkfat
Moshe Rosenberg, UC Davis
A broad array of different rheological properties of whey protein gels can be achieved by incorporating selected factions of fractionated milkfat in the gel to yield a composite gel. The specific objectives of this research are to:
- Study and quantify the affects of filler (fractionated milkfat fractions) composition and physico-chemical properties matrix (whey proteins) composition and matrix-filler interactions on the rheological properties and structural features of composite gels consisting of whey proteins and fractionated milkfat fractions.
- Based on the results of the first objective, develop a series of model whey protein-based, fractionated milkfat-containing composite gels that significantly differ from each other, as well as from protein-only gels, in their viscoelastic and compressive properties.
Our research has been focused on investigating and developing new data and understanding the influence of protein composition on the matrix of the gel (continuous network) and on the melting properties of the included lipid filler phase on the rheological (viscoelastic) properties of the gels. Using commercially available fractionated whey proteins and an array of milkfat fractions that differ significantly in their melting properties, we developed a series of model gels. The gels contained 10–15 percent total protein content, consisting of different proportions of the major whey protein constituents, a-lactalbumin and b-lactoglobulins. Additionally, the selected lipid fraction was incorporated in all of the different protein compositions at a lipid load of 10–30 percent (w/w). Protein composition of gels was modulated to represent an array of different mass ratios of the whey proteins ranging from 0 to 100 percent. Using dynamic rheological measurements within the linear viscoelastic range, we investigated the effect of protein content, protein composition, lipid load and temperature on the manifestation of elastic, viscous, stiffness and relative viscoelastisity in the gels. Results indicated that the viscoelastic properties of the gels were profoundly influenced by the above variables. Results suggest the important role of b-lactoglobulin in affecting the elastic properties of the matrix gels and the role of a-lactalbumin in affecting the viscous properties of the gels. Results indicate the significant role of lipid load and melting properties in affecting both viscous and elastic properties of the composite gels. Also, results established data that allows preparing an array of gels manifesting significantly different rheological properties that also differ from those of WPI-Based gels. Selecting and adjusting protein composition and lipid type and load provides a means for developing a wide range of engineered emulsion gels with significantly different rheological properties. The results can provide new means to meet desired texture profiles (needed in different applications) of whey-protein based gels and in developing new rheological profiles of such gels. The resulting understanding, applicable information, and model systems will allow the introduction of new applications for fractionated whey proteins and fractionated milk components as functional ingredients as well as expending existing applications for whey proteins beyond those that already exist.
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