Milk phospholipids

In average, milk contains about 33 g total lipid (fat)/l. Phospholipids and glycosphingolipids accounts to about 1% of total milk lipids. These lipids contain relatively larger quantities of polyunsaturated fatty acids than the triacylglycerols.

Phospholipids contain phosphorus in their molecules in addition to the fatty acids and glycerol; they also contain a nitrogenous base.

Phospholipids are basic constituents of natural membranes; their amphiphilic properties derive from the presence of both a hydrophobic tail and a hydrophilic head. Phospholipids are a type of fat present in plant and animal cells.

Principally milk phospholipids are the Lecithin, Cephalin and Sphingomyelin. Though fat-soluble, they are hydrophilic and imbibe large quantity of water and swell. They are used as antioxidants for fat rich dairy products.

Phospholipids are a vital component of cell membranes, which separate the interior of cells from the outside environment and give cells structure. They are the main constituents of the milk fat globule membrane (MFGM), which encircles the lipid droplets secreted by the mammary gland cells. The MFGM contains about 60 to 70% of all milk polar lipids. These are largely responsible for the stability of fat globules in the milk oil/water emulsion, due to their amphiphilic nature.

In human diet, phospholipids are also needed to support the absorption of fats and fat-soluble nutrients, like omega-3 fatty acids.
Milk phospholipids

Milk fat composition

Milk fat is a source of energy for human being including infants, children and adults. It is the major component for the growth and generation of energy for infants. The fats including cholesterol is necessary for cell membranes especially for brain ones.

Milk fat is one of the most complex of all common fats, composed of about 98% triglycerides. It contains numerous fatty acids, mainly saturated (66%), but also monosaturated (30%) and polyunsaturated (4%).

Phospholipids are about .5 to 1% of total lipids, and· sterols are .2 to .5%. These are mostly located in the globule membrane. Cholesterol is the major sterol at 10 to 20 mg/dl.

The saturated fatty acid present in higher quantity on milk is the palmitic (C16:0), which represents round 40% of the total saturated fatty acid. Related to the amount of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acid (PUFA), the oleic (C18:1) and the linoleic (C18:2) acids are the most representatives.

Milk fatty acid composition can be influenced by several factors, many of which are interactive. These include stage of lactation, seasonal variation, low milk fat syndrome, feeding, genetic variation, and changes in the energy status of the cow due to administration of bovine somatotropin.
Milk fat composition

Separation of fat or cream from milk

Most milk plants separate milk for standardization or the obtain cream for bottling purpose and skim milk for butter milk and cottage cheese.

A layer of cream will form on the top of fresh milk, as it comes from cow, if it is allowed to stand for twenty or thirty minutes. This known as gravity creaming and it was very important prior to the invention of the cream separator. For many years it was customary to heat milk to 85 to 95 °F separation, because at this temperature the difference in density between the fat and skim milk is greatest and results in the most efficient separation of fat from skim milk.

Cream is separated from milk in a cream separator. Cream separator is a heavy metal bowl spinning at a very high speed which sediments the skim milk phase of incoming milk toward the wall of the bowl and displaces the cream inward along the centre of the bowl.

The cream and skim milk can then be recombined in desired ratios to obtain low-fat, light and whole milk with 1%, 2% and 3.25% fat respectively. This standardization usually is performed in a continuous manner.
Separation of fat or cream from milk

What is the meaning of filled milk?

Unsweetened and sweetened condensed milk can be made from fresh milk or recombined milk (nonfat dry milk, fat and water). When the source of fat is other than butterfat, the resultant milk is called filled milk.

Filled imitation dairy products are made in semblance of a dairy product. A vegetable or animal fat is used to substitute for milk fat.

Today, filled milk can be found on the canned milk shelved of any supermarket. Fat-filled powders are frequently manufactured for use as alternatives to whole milk, in both human and animal nutrition.

For human consumption filled milk powder contain 26 to 28% fat and are used for reconstitution, either domestically or by caterer. The type of vegetable oil, or oils sued will depended on nutritional requirements of the product, as different oils can be used to achieve a given fatty acid profile and given ratios of saturated, mono unsaturated and poly-unsaturated fats.

For animal feeding, fat filled milk powder contain 30 to 50% fat and up to 2% of emulsifying agent e.g. lecithin, monoglycerides.

Hardened palm kernel and coconut oils have commonly been used in fat-filled milk powder production but selectively hydrogenated rapeseed oil has found favor in grounds of cost.

While it contained no butterfat, filled milk had the same taste, odor, color consistency, specific gravity and cooking qualities as ordinary evaporated whole milk.
What is the meaning of filled milk?

Nutrient in low fat milk

The term ‘milk’ is synonymously with whole milk, which must contain not less than 3.25% milk fat and 8.25% solids not fat.

Fat provides a perception of creaminess and improves the mouth feel of acid dairy products.

Fat reduce milks are labeled according to their contribution of grams of fat per reference amount (RA) of 240 mL. Low fat milk contributes less than 3 g fat per RA, while nonfat milk contributes less than 0.5 g of fat per RA.

Low fat milk contains 0.5%, 1.5% or 2% milk fat and not less than 8.25 percent nonfat solids.  Though it contains 2% fat by weight, this amount is equivalent to 30 percent of the total calories. Sometimes low-fat milk is fortified with nonfat dry milk.

One cup of low fat milk provides 121 calories; protein, 8.1 g; carbohydrate, 11.7 g; calcium, 297 mg; fat, 4.8 g; cholesterol, 22 mg; vitamin A, 140 retinal equivalents; thiamin, 0.1 mg; riboflavin, 0.4 mg; niacin, 0.21 mg.
Nutrient in low fat milk 

Nutrients in Milk

Nutrients in Milk 

Lactose It is the principal and typical carbohydrate of milk, known as milk sugar. Glucose, galactose and other sugars such as oligosaccharides are also present in traces. Lactose exists in true solution in milk. It is a disaccharide, composed of two molecules of monosaccharides; glucose, and galactose. Lactose is readily fermented by the lactic acid fermenting bacteria producing lactic acid and has significance in milk and milk products. It exists in two isomeric forms, designated as α and β forms of which the β form is more soluble than the alpha form in water. Lactose content of cow milk is 4.9 percent. The lactose content of milk is inversely proportional to the ash content of the milk. Udder infection promotes an increased level of chloride in the milk and depresses the secretion of lactose.

Proteins Milk protein is a rich source of essential amino acids. Whey proteins are proteins that are passed along with the whey portion after the coagulation of milk. They contain 51% essential amino acids when compared to 45% in casein. The sulphur containing amino acids, which are considered essential and important, are found in higher concentration in whey protein than in casein. Usually the quality of egg proteins are regarded as very high. But the net protein utilization, biological value and the protein efficiency ratio of milk protein come neck in neck with the quality of egg protein. Lactalbumin, a whey protein , whose biological value, net protein utilization and protein efficiency ratio is considered superior when compared to the major milk protein, casein. Normally double the quantum of vegetable protein is required to meet the daily requirement of essential amino acids when compared to that obtained from the milk proteins.

Casein May be defined as the major protein, which is precipitated at pH 4.6 and is exclusive to milk. It is present in spherical bodies as micelles, which vary in size with negative surface charge. The caseins of milk may be sub-divided into five main classes, αs1, αs2, β, gamma and k-caseins. In milk, casein is present in combination with calcium in the form of calcium caseinate or more precisely calcium hydrogen caseinate.

Whey proteins Are those in the whey fraction, after the precipitation of casein at pH 4.6. These are the alpha-lactalbumin, beta-lactoglobulin, immunoglobulins, lactoferrin, transferrin, proteose-peptone fractions etc. Most of these are globular proteins subject to heat denaturation. α-lactalbumin exists in variants A and B forms and is susceptible to denaturation by unfolding of the tertiary structure. β-lactoglobulin is identical to blood globulin and insoluble in water and is responsible for the transfer of antibodies. Normal milk contains 0.1%, whereas colostrum contains 6 %.

Milk fat The digestibility of milk is comparatively higher than other oils and fats. This can be attributed to existence of fat globules in aqueous phase forming an emulsion. This facilitates its easy absorption through the intestinal tract when compared to other fats which have to be emulsified with bile salts, enzymes from pancreas and fat splitting lipases. Endowed with short and medium chain fatty acids, milk fat can be easily absorbed when compared to long chain fatty acids because of the ability of the lipases to split the ester bonds in the former. Supplementation of milk fat in the diet increases the energy density. When compared to human milk, the cow milk is low in essential fatty acids such as linoleic and linolenic acids. Short and medium chain fatty acids with 4-12 carbon atoms, which occur at comparatively higher concentration in milk fat, reported to have antibacterial and fungistatic activity. Milk fat plays another important role in preventing tooth decay by forming a protective coat over the surface of enamel. It is composed of triglycerides of fatty acids. A fatty acid molecule is composed of hydrocarbon chain and carboxyl group. Triglycerides are of two types, simple and complex. In simple, all the three fatty acids are of same nature, whereas complex triglycerides on hydrolysis give glycerol and different fatty acids. The milk fat exists in the form of small globules of sizes ranging from 2 to 10 microns with different glycerides of low melting points in suspension. Milk fat varies in amount and composition, according to the breed, species, feed and lactation time, of which, feed being a major factor. Fat is distributed in globules as triglycerides (98-99 %), fat globule membrane in combination with phospholipids and lipoprotein (0.2 to 1.0 %) and also as free fatty acids, cholesterol and phospholipids in the serum.

Phospholipids These contain phosphorus in their molecules in addition to the fatty acids and glycerol; they also contain a nitrogenous base. Principally milk phospholipids are the Lecithin, Cephalin and Sphingomyelin. Though fat-soluble, they are hydrophilic and imbibe large quantity of water and swell. They are used as antioxidants for fat rich dairy products.

Vitamins Various vitamins present in milk are as follows. Fat Soluble Vitamins - include vitamins A, D, E and K. Water-soluble vitamins are the, B1 (thiamine), B2 (riboflavin), B6 (pyridoxine), Biotin, Niacin (nicotinic acid), Pantothenic Acid, Para-amino benzoic acid, Inositol, Choline, Folic acid, B12, and Ascorbic acid. Fat rich milk products contain large quantities of fat soluble vitamins, whereas whole milk, skim milk, buttermilk and whey are a good source of water soluble vitamins.

Minerals The portion left after ashing of milk at 150ºC is known as the 'ash of milk' and is composed of various inorganic constituents. Ash forms about 0.75 % of milk and plays a very important role in milk and is basic in character. The minerals in milk consist principally of the chlorides, citrates and bicarbonates of calcium, magnesium, potassium and sodium.

Nutrients in Milk Article Source: http://EzineArticles.com By Thenmozhi Kathirvelu