Phospholipids in Milk: Essential Roles in Nutrition and Stability

Milk, a staple in many diets worldwide, contains approximately 33 grams of total lipids per liter. Within these lipids, phospholipids and glycosphingolipids make up around 1%. Despite their small proportion, these lipids are significant due to their composition and function. Unlike triacylglycerols, phospholipids and glycosphingolipids contain higher quantities of polyunsaturated fatty acids, which are beneficial for health.

Phospholipids are unique because they contain phosphorus in addition to fatty acids and glycerol, along with a nitrogenous base. This molecular structure grants them amphiphilic properties, featuring both hydrophobic tails and hydrophilic heads, making them essential constituents of natural membranes. These properties enable phospholipids to function effectively within cell membranes, providing structural integrity and facilitating the selective permeability necessary for cellular function.

In milk, the primary phospholipids are lecithin, cephalin, and sphingomyelin. Though these phospholipids are fat-soluble, they are also hydrophilic, allowing them to absorb large quantities of water and swell. This characteristic makes them valuable as antioxidants in fat-rich dairy products, enhancing product stability and shelf life. Furthermore, phospholipids are crucial for the formation and maintenance of the milk fat globule membrane (MFGM). This membrane, which envelops lipid droplets secreted by mammary gland cells, consists of 60 to 70% of all milk polar lipids and plays a vital role in stabilizing fat globules in the milk's oil/water emulsion.

In addition to their structural and functional roles in milk, phospholipids are essential in the human diet. They facilitate the absorption of fats and fat-soluble nutrients, such as omega-3 fatty acids, which are important for maintaining overall health. The amphiphilic nature of phospholipids ensures that these nutrients are effectively absorbed and utilized by the body, supporting various physiological functions.

In summary, while phospholipids and glycosphingolipids constitute a small percentage of milk lipids, their contributions are substantial. They not only enhance the stability and quality of dairy products but also play a critical role in human nutrition and cellular function.
Phospholipids in Milk: Essential Roles in Nutrition and Stability

Composition of Cow’s Milk: Nature's Complete Nutrient Package

Cow’s milk is a remarkable fluid, consisting predominantly of water at approximately 87%, with the remaining 13% encompassing vital milk solids. These milk solids comprise two major components: butterfat and solids not fat (SNF), collectively contributing to the milk's nutrient richness and versatility.

The fat portion, also known as butterfat, constitutes about 3.7% of cow’s milk. This fat content can slightly vary depending on the breed, with Ayrshire, Brown Swiss, Guernsey, and Jersey cows generally yielding milk with slightly higher fat content compared to Holstein cows. Despite these variations, Holstein cows, renowned for their high milk production, remain a dominant source of milk globally.

The SNF portion, accounting for 8.9% of the milk, is where the essence of milk's nutritional value lies. SNF can be further categorized into lactose (milk sugar), essential minerals (such as calcium, potassium, and phosphorus), and proteins (including casein and whey proteins).

The protein content in milk, constituting approximately 3.3% of its composition, primarily consists of casein and whey proteins. Casein, representing 77% of the total protein content, is unique for its role in forming micelles—complex structures essential for transporting calcium and phosphate. Meanwhile, whey proteins complement the nutritional profile with their high-quality amino acids, crucial for growth and tissue maintenance.

Furthermore, cow’s milk is revered as a nutrient-dense food due to its balanced composition of essential nutrients relative to its caloric content. It stands out as the quintessential complete food, even containing trace amounts of essential vitamins and minerals vital for human health.

However, the suitability of milk can vary across species due to differences in lactose composition. Some young mammals might face lactose intolerance issues when exposed to milk from different species.

In summary, cow’s milk is a nutritional powerhouse, providing an array of vital nutrients essential for growth and development. Its varied composition, influenced by breed and species, underscores its significance in global agriculture and nutrition. Whether it’s for sustenance in infancy or as a staple in adulthood, cow’s milk remains unparalleled as a source of nourishment, offering a comprehensive blend of nature's finest nutrients.
Composition of Cow’s Milk: Nature's Complete Nutrient Package

Lactoperoxidase: Antimicrobial Milk Enzyme

Lactoperoxidase, a heme-containing glycoprotein, is found in the milk of most mammals and various bodily fluids such as tears and saliva. This antimicrobial protein is produced by mammary, salivary, and mucosal glands.

In its catalytic center, this enzyme binds a heme prosthetic group derived from protoporphyrin IX, placing it in the category of mammalian heme-containing peroxidase (XPO) enzymes.

Activated by H2O2, lactoperoxidase has been utilized to impede the growth of microbes in raw milk, particularly in regions where refrigeration is not feasible.

The lactoperoxidase system plays a vital role in the innate immune system by eradicating bacteria in milk and mucosal secretions, suggesting potential therapeutic applications through system enhancement.

This system exhibits antimicrobial efficacy against a diverse range of microorganisms responsible for milk spoilage and diseases, including bacteria, the HIV-1 virus, molds, yeasts, mycoplasma, and protozoa. Notably, the lactoperoxidase system does not support the growth of pathogenic microorganisms once the bacteriostatic effect has concluded.
Lactoperoxidase: Antimicrobial Milk Enzyme

High Temperature Short Time (HTST)

Pasteurization is an established process invented by Louis Pasteur in 1864. Milk should be free from toxins and pathogens and also it must retain all nutrients and vitamins with extended period of storage life. To achieve the above said criteria, milk is heated to a particular temperature for a brief time then cooling it down once more quickly.

The most common types of milk pasteurization process are Batch Pasteurization, High Temperature Short Time (HTST) and Ultra High Temperature (UHT).

HTST pasteurization is an effective method of making milk safe for consumption, without unduly changing either its sensory characteristics or its nutritional value. In this method the heating of every particle of milk to at least 72°C and holding for at least 15 seconds.

Real-time HTST process consists of three integrated sections, (a) plate-heat-exchanger engaged in regeneration, heating and cooling (b) holding tank, and (c) holding tube.

An HTST system includes a balance tank, an efficient heat exchanger to bring milk to pasteurization temperature and to cool it afterward, a means to maintain a constant flow through the system (e.g., a timing pump), a holding tube where the product is held at pasteurization temperature for the required time.
High Temperature Short Time (HTST)

Dairy product: Kumis

Kumis or kumiss or koumiss is a fermented dairy product traditionally produced using mare’s milk. The drink remains important to the people of the Central Asian steppes, including the Turks, Bashkirs, Kazakhs, Kyrgyz, Mongols, Yakuts and Uzbeks.

It is produced commercially in Central Asia. Although it is traditionally made from mare’s milk, modern industrial variants may use cow’s milk instead.

Mare’s milk contains higher sugar (about 7%) than those of cow’s milk (4.5%). Kumis has higher levels of alcohol (ca. 2%) than kefir (ca.0.5%).

Kumis is a dairy product similar to kefir, but is produced from liquid starter culture, in contrast to the solid kefir ‘grains’.

In addition of the fermentation of lactose by yoghurt starter bacteria and Torula kumis, proteolysis is observed during manufacture of kumis due to complex microflora and the proteolysis contributes to flavor of kumis.

Traditionally, kumis is fermented in a horsehide bag or pouch. Mares would be milked in the spring and summer months after foaling. Approximately half of the horse’s milk would be used in kumis production.

Kumis cure has been applied for patients for treatment of intestinal and chronic deceases.
Dairy product: Kumis

Raw milk associated with Campylobacter jejuni

Raw milk is a common source of infections. The bacterial are often carried by healthy cattle and by flies on farms. Non-chlorinated water may also be a source of infections. However, properly cooking chicken, pasteurising milk, and chlorinating drinking water will kill the bacteria.

Raw milk may become contaminated with C. jejuni in one of two ways. It may excreted directly by a mastitis udder or feces may contaminated the product.

Contamination of milk from C. jejuni mastitis is thought to be rare, but direct milk excretion leading to human cases has been reported.

Milkborne campylobacteriossis outbreaks have even almost invariably associated with consumption of raw or inadequately pasteurised cow’s milk.

However, a few cases of C. jejuni and E. coli enteritis have been trace to ingestion of raw goats milk in United States, Great Britain and Australia, with the epidemic strain identified in fecal samples from incriminated goats.
Raw milk associated with Campylobacter jejuni

Definition of Grade A pasteurized milk and milk product

This is Grade A raw milk which has been pasteurized in accordance with the regulations of the US Public Health Service Pasteurized Milk Ordinance and Code. Such milk must meet all the regulations, pasteurization confirmation tests, and sanitary requirements for this grade.

Temperature
Cooled to 45 ° C or less and maintained thereat

Total bacterial count
Milk and milk products < 20000 per ml

Coliform count
Not exceeding 10 per ml: provided that in the case of bulk milk transport tank shipment, shall not exceed 100 per ml.

Phosphatase
Less than 1 mg per ml, by Scharger Rapid method (or equivalent by other means)

Antibiotics
No detectable zone by Sarcina lutea Cylinder Plate Method or equivalent.
Definition of Grade A pasteurized milk and milk product

Nutrition of kumiss

Kumiss is a fermented milk product found in Russia where it’s commonly made from the milk of mares. Limited availability of mare’s milk has led to the development of kumiss from cow’s milk.

Because of the composition of mare’s milk, finished kumiss has a uniform consistency with no tendency to whey-off.

Kumiss is considered a very nutritious and rehabilitative drink. The biological value of kumiss is based e.g. on its high-quality protein, easily absorbable fat and lactic acid and vitamin content.

The final product has an acidity of 0.9 – 1.25% titratable acidity and contains between 0.5 and 2.5% alcohol. Kumiss is regard as a dietetic product and is used to treat GI disorders.

By the year 1215, Genghis Khan conquered Mongolia, and Khan personally believed that part of his military success could be attributed to the fact that his army stayed strong and healthy by consuming the nutritious product, kumiss.
Nutrition of kumiss

What is imitation milk?

Imitation milks can be manufactured to resemble milk and be used in place of milk. These products resemble whole milk but contain no actual milk ingredients. They generally contain water, vegetable fats, corn sugar, starch, vegetable protein, sodium caseinate, and stabilizers, such as gums or alginates.

Vitamins and minerals may be added to the product to improve the nutritional value. Imitation milks usually do not taste like whole milk and often require the addition of flavorings.

An imitation milk product may look and taste like the traditional product, yet is nutritionally inferior. Specifying the term ‘imitational’ on labels is no longer a legal requirement.

Imitation milks are lactose-free and so are useful for people with lactase deficiency, but sometimes sodium caseinate and whey are added, which makes these products inappropriate for people with milk-protein allergies.

The vegetable fat, like milk fat, may be high in saturated fatty acids from coconut or palm oils used in the manufacture of these products.

Both imitation and filled milks are used as a basis for formulation of synthetic and semisynthetic of flavored milk drinks, ice cream, and other frozen desserts, butter, cream cheese, coffee cream, whipped cream, and other imitation dairy products.

All these products are processed, stored and distributed in a manner similar to that of the dairy products that they resemble. Coffee whiteners or lighteners are popular among consumers because of their excellent storage life. Such longevity is a distinct advantage to people who rarely use ice cream.
What is imitation milk?

Minerals in milk

Milk is important source of growth-supporting mineral, also referred to as type II nutrients, such as potassium, magnesium, phosphorus and zinc. Milk contains about 30 different minerals, but only a few of them are present in greater than trace amounts.

The normal levels of the major mineral constituents of cow’s milk are listed below. These are average values; there is a considerable natural variation in the levels of these constituents.

The two most abundant are calcium and phosphorus. Calcium constitutes about 30 percent of the total minerals in milk. In turn about 30 percent of the total calcium is soluble.

Milk also an important source of phosphorus. This essential mineral plays a central role in metabolism and is a component of lipids, proteins and carbohydrates.

A number of factors influence the variations in salt composition, such as feed, season, breed and individually of the cow, stages of lactation and udder infections.
Minerals in milk

Drum drying processing of milk

The main drying process of skim milk powder and whole milk powder is spray drying. However, drum drying and fluid-bed drying are used for special purposes.

In drum drying the milk is distributed on rotating, steam-heated drums, where the water evaporates.

Drum dryers were introduced into industries about 100 years ago and it starting with the double-drum dryer which features the feeding by nipping between two drums. J. A Just was one of the first inventors to receive –patent rights on a drum dryer with two rolls in 1902.

Drum dryer consists of one or more hollow metal cylindrical rolls or drums that are mounted to rotate on horizontal axes at a variable speed.

Using film evaporating systems, the milk is first pre-concentrated to 40-50% solids. A thin layer or film of product is dried over an internally steam-heated drum with steam pressure up to 620 kPa and 149 °C. Approximately 1.2 – 1.3 kg steam are required per kilogram of water evaporated.

The film dries as the drum rotates. The dried milk then is scraped from the drum surface, as they rotate, by metal scraper. The feeding materials can be slurries, paste, or solutions and final dried products are in the form of powders, flakes or chips.

The operating variables for a drum dryer include condensation of incoming product in an elevator, temperature of incoming product, steam pressure in drum, speed of drum, and height of product over drum.

In the process, relatively large particles are obtained.  It has poor dissolving properties and where sold for domestic use is subjected to further instantisation, which agglomerates granules and leads to a faster dissolution time.
Drum drying processing of milk 

Food sources of calcium

Early humans are thought to have consumed a diet rich in calcium from a wide range of plant sources.

Milk and dairy products are the richest food source of calcium.  In the last few years, an enormous increase in diversity of food sources of calcium has become available in North America through extensive fortification.

Milk and other dairy foods provided 84% of the calcium from foods in the United States in 1889-1993. Milk and milk products such as yoghurt and cheeses are outstanding sources of calcium.

Now, calcium requirements can be met through consumption: naturally occurring foods, calcium-fortified foods, and supplements.

There are also food plants contain plenty of calcium that is highly bioavailable: cauliflower, watercress, parsley, Brussels sprouts, rutabaga, kale, mustard greens, bok choy, broccoli and turnip greens.

Eventhough green leafy vegetables contain less calcium per serving than milk, but calcium in these vegetables is absorbed well or slightly better than calcium from milk.

Although slightly less bioavailable, calcium is also abundant in almonds, sesame seeds, pinto beans and sweet potatoes. Mineral waters are also often a good natural source of calcium.
Food sources of calcium

Fat in ice cream

The main ingredients provide the required sensory properties: ice gives cooling, fat provides creaminess, air gives lightness and softness, sugar provides sweetness and flavors enhance its taste.

Milk fat or butterfat, as it is sometimes called, is the most important component of ice cream. It is also the most expensive major ingredient of ice cream, and so the higher the fat content, generally the more expensive the product.

Milk fat gives ice cream a rich and creamy flavor. Fat also contributes to producing a smooth texture and greater resistance to melting.

The fat also is a concentrated source of calories and contributes heavily to the energy value of ice cream.

A milk fat content between 14% and 22% is ideal for producing a rich tasting, full bodied ice cream. According to US standards, ice cream must contain at least 10% milk fat, before the addition of bulky ingredients and must weigh a minimum of 4.5 pounds to the gallon. Ice cream made with less than 14% milk fat is weak-bodied coarse and icy.

Decreasing the fat content of ice cream decreases the creamy sensation and increases the intensities of flavors of skim milk powder and of corn syrup.

It also impacts on added flavors, since there are many flavor components that are fat soluble, which are released to the olfactory senses as fat melts.
Fat in ice cream

Disaccharide sugar of lactose

In disaccharides, pairs of single sugars are linked together. Three disaccharides are important in nutrition: maltose, sucrose and lactose.

Lactose is the principal carbohydrate of milk. Lactose, the 12-carbon sugar present in milk, is broken down in the intestine to glucose and galactose (6-carbon sugars), both of which can be used as sources of energy and exist in two anomeric forms of which the α-form predominates.

It is the only sugar not found in plants, it is found in milk; hence, it is called milk sugar. Lactose gives milk and other dairy products a slightly sweet taste.

Most human infants are born with digestive enzymes necessary to split lactose into its two monosaccharide parts, glucose and galactose, so as to absorb it.

Lactose is probably the most troublesome disaccharides as some people lack of the enzyme lactase which splits the molecule glucose and galactose. These people may experience nausea, bloating, abdominal pain or cramping, diarrhea or excessive gas after drinking milk or eating lactose-containing products.

Lactose also facilitates the absorption of calcium and promotes the growth of beneficial bacteria in the intestines.
Disaccharide sugar of lactose

Fat globules in milk

The milk fat included in the globules is the major native form of milk fat. The milk fat globule is a spherical particle that is the form in which milk fat is secreted in milk. The physical, chemical and technological properties of milk fat globules are influenced by their size.

In milk as secreted by the cow these globules average about 10 microns in diameter, with a range from 0.1 microns to ~15 microns. The globules were significantly higher in the milk with the highest fat content.

Milk fat globule membrane is a delicate structure and can easily be ruptured by either physical or thermal shock. It forms around fat globules as they pass from secretory cells in the cow’s udder into the milk. All interactions between fats and plasma must take place through the membrane.

When the milk fat globule membrane is intact, it protects the fat exposure to naturally occurring lipase enzymes and the resulting development of a rancid off-flavor. T

he density of the milk fat globules is much lower than that of the m ilk serum and as a result, milk fat globules rise at form a fat rich phase, a process commonly called creaming.

In the globule, fatty fractions e.g. sterols, triglycerides that are less soluble in water are found in the interior of the globule.

The lipids of milk fat serve nutritionally as an energy source, act as a solvent for the fat soluble vitamins and supply essential fatty acids.
Fat globules in milk

Casein in milk

A method for the preparation of protein from milk by acid precipitation was described in 1838 by J.G Mulder, who coined the term ‘protein’. The acid-precipitated protein is referred to as casein.

Casein is the primary protein of milk comprising approximately 80% of the milk protein.  It is found in no product other than milk.

Beta casein is one of the major caseins in cow’s milk. Broadly, beta casein may be present as either A1 or A2 beta casein. Most cow in Australia produce milk with a combination of A2 and A1 beta-casein.

Casein is a phosphorus-containing protein that is heat stable, but precipitated by alcohol, rennet and acids.

The caseins are actually a group of similar proteins, which can be separated from the other milk proteins by acidification to a pH of 4.6.

At this pH, the caseins aggregate, since they are hydrophobic, are poorly hydrated and carry no net charge.

Individual fractions are combined into larger units called casein micelles, structure and stability of which are related to calcium content.

Casein in uncooled cow’s milk is present in spherical particles with a diameter of about 20 to 600 nm, comprised of 20 to 150,000 casein molecules. The inorganic matter of casein micelles, mainly colloidal calcium phosphate, is about 8 g/100 g casein,

In cheese making, most of the casein is recovered with the milk fat.
Casein in milk

What is toffee?

Toffee is buttery rich, very crunchy creation. A good toffee has equal or nearly equal amounts of butter and sugar and a large helping of nuts to impart their special flavor.

Like hard candy and brittle, toffee is a sugar candy cooked to a high temperature. Toffee contains dairy products which provide its caramel color and flavor through cooking.

All toffees contain skim milk solids and usually some fat. A toffee can be and using full cream milk and butter or with skim milk and vegetable fat – some toffees lie somewhere in between the two extreme.

Toffee made using higher fat dairy products has a crisp and delicate texture, while toffee made lower fat ingredients has more of a hard candy texture.

A special ingredient for toffee recipe is soy lecithin. In toffee, soy lecithin prevents the fats from separating and creating an oily residue.

A few toffees are extremely hard: they are in the glassy state. Most toffees are chewable rather than glassy.

They are made with sugar, glucose syrup and some form of milk. They referred form of milk for making toffees is sweetened condensed milk, either full cream or skimmed.
What is toffee?

Low fat milk processing

Centrifuge or milk separator is designed to separate the cream from the milk as soon as drawn from the cow.

The milk is heated in a plate heat exchanger to approximately 57° C and subsequently separated into a high fat fraction and low fat fraction.

The centrifuges rotates at a high speed and this facilities the separation of oil or fat from the milk. Fat being lighter floats to the top and the remaining milk solution being heavy remains at the bottom.

The fat rich cream after skimmed off is to be used for the manufacturer of butter, butter oil, ghee or other fat rich products.

The principle used in separation by centrifugation is the difference in the density of the component of a mixtures.

The process of separating has not really changed since the first invention of the centrifuge at the end of the nineteenth century. However, the reliability of equipment and the scale at which these process are run are far beyond the imagination of the inventors.

Low fat milk are as nutritious as whole milk, but contain much less fat and cholesterol than whole milk. Low fat milks may contain 1% or 2% fat.

Because fat soluble vitamins are removed when fat is separated, the new federals standard for low fat milk required addition of vitamin A. The lower fat content drops the calories to 299 per cup.
Low fat milk processing

Whey protein of milk

Whey is the fluid remaining following precipitation of casein micelles. Whey is typically a by-product formed after the fat and casein have been removed from the milk in cheese and casein production.

Whey protein makes up approximately 20% of milk protein and includes the alpha-lactalbumins and beta-lactoglobulins A and B. Other components are bovine serum albumin BSA, immunoglobulin and protease peptones.

Beta-lactoglobulins and alpha-lactalbumins are primarily responsible for the physiochemical properties of whey proteins.

Whey proteins are more hydrated than casein and are denatured and precipitated by heat rather than by acid.

Because alpha-lactalbumins has low solubility but good water absorption characteristics after heating, it is used widely in bakery products, meats, yoghurts and processed cheese.

High level of denatured whey proteins in cheese milk may exploited as a means on improving the texture of low-fat cheeses, which tend to be too firm and rubbery, compared with their full-fat equivalents.
Whey protein of milk

Low fat milk processing

Centrifuge or milk separator is designed to separate the cream from the milk as soon as drawn from the cow.

The milk is heated in a plate heat exchanger to approximately 57° C and subsequently separated into a high fat fraction and low fat fraction.

The centrifuges rotates at a high speed and this facilities the separation of oil or fat from the milk. Fat being lighter floats to the top and the remaining milk solution being heavy remains at the bottom.

The fat rich cream after skimmed off is to be used for the manufacturer of butter, butter oil, ghee or other fat rich products.

The principle used in separation by centrifugation is the difference in the density of the component of a mixtures.

The process of separating has not really changed since the first invention of the centrifuge at the end of the nineteenth century. However, the reliability of equipment and the scale at which these process are run are far beyond the imagination of the inventors.

Low fat milk are as nutritious as whole milk, but contain much less fat and cholesterol than whole milk. Low fat milks may contain 1% or 2% fat.

Because fat soluble vitamins are removed when fat is separated, the new federals standard for low fat milk required addition of vitamin A. The lower fat content drops the calories to 299 per cup.
Low fat milk processing