Milk and dairy foods

Milk is the secreted fluid of the mammary glands of female mammals. It contains nearly all the nutrients necessary to sustain life. Since the earliest times, mankind has used the milk of goats, sheep and cows as food. Milk is basically composed of water (~87 percent), milk fat (~4 percent) and non-fat solids (~9 percent).

In addition to milk, several dairy products such as cream, butter, yogurt, kefir, and cheese have been produced and consumed worldwide for millennia.

Fresh milk is highly perishable, bulky, and easily contaminated (it is a favorable medium for bacterial growth). Because it is so susceptible to contamination and adulteration (with water), fluid milk production, treatment and distribution is widely subject to controls.

Milk tastes mildly sweet, while its odor and flavor are normally quite faint. Cow milk generally contains between 3 and 4 g of fat/100 g, although values as high as 5.5 g/100 g have been reported in raw milk. Most milks consumed now contain a standardized fat content of around 3.5 g/100 g.

Milk fat occurs in the form of droplets or globules, surrounded by a membrane and emulsified in milk serum (also called whey). The fat globules (called cream) separate after prolonged storage or after centrifugation. The fat globules float on the skim milk. Homogenization of milk so finely divides and emulsifies the fat globules that cream separation does not occur even after prolonged standing.

The major proteins found in milk are casein and whey proteins, with casein (αs1-, αs2-, β-, and κ-casein) accounting for approximately 78 percent of the protein in cow milk and whey proteins accounting for about 17 percent of the total protein

Milk and dairy products are nutrient-dense foods, supplying energy and high-quality protein with a range of essential micronutrients (especially calcium, magnesium, potassium, zinc, and phosphorus) in an easily absorbed form. Milk minerals are crucial for human health and development as well as in dairy processes as cheese-making and for all traits involving salt-protein interactions.

In recent decades, technological advances have supported the development of new dairy-based products. Broadly, dairy products can be categorized as basic products, such as fermented milk, cheese and yoghurt, and value-added products, such as low-fat and fortified milks.

Milk can be internationally traded either in dry, evaporated or condensed whole milk form or as dry skimmed milk powder (NFDM). These whole milk products may be reconstituted to fluid milk by mixing with water. Skimmed milk powder is reconstituted by mixing with butteroil (anhydrous milk fat) or vegetable fats and water to obtain a mixture of about 3.5 to 4 percent fat and 9 percent non-fat-solids. Well-reconstituted milk is said to be practically indistinguishable from fresh milk.
Milk and dairy foods

What is red meat?

Red meat is commonly considered to include beef, veal, pork and lamb (fresh, minced and frozen). In recent years, red meat has attracted much debate regarding its impact on health and the environment. Consumption trends of meat vary greatly around the world. Significant increases in consumption are apparent in developing countries with Latin America, the Caribbean and East Asia seeing particularly large increases.

Red meat continues to play an important role in the human diet today; it contains high biological value (easily absorbed and utilized) proteins and essential micronutrients, including vitamins and minerals. The composition of the meat varies based on the animal species, sex, age, and diet, as well as the climate and activity during its growth. Total nitrogen, fat, and iron levels increase as the animal approaches maturity. It also makes a significant contribution to the monounsaturated and omega 3 fatty acids in our diet.

In addition, the ratio of polyunsaturated fatty acids (PUFAs) to saturated fatty acids (SFAs) decreases with the maturity of the animal.

In terms of micronutrients, red meat (particularly beef and lamb) is an excellent source of bioavailable iron and zinc, and also provides selenium, vitamin D, and B vitamins, with red meat being one of our major sources of vitamin B12. Red meat also contains bioactive compounds such as taurine, carnitine, creatine and some endogenous antioxidants.
What is red meat?

What is meant by coconut cream?

Coconut cream is essentially a thick paste-like version of coconut milk, it is the first press of coconut and water. Similar as with cow’s milk, the coconut milk is left standing for a while with the cream separating on the top of the milk.

The amount of water added to the grated coconut determines whether to get cream or milk. It is usually to add very little water for the first squeeze to get what is called first milk or coconut cream.

The second thinner yield when more water has been added is called the second milk or just coconut milk.

Coconut milk usually contains about 17 percent fat, while coconut cream contains about 21 to 24 percent fat.

Commercial coconut creams are usually sold in cans, and the main ingredient in these products is almost always water. The dietary fiber of the coconut has usually been stripped out of these commercially available products as well.

Coconut cream concentrate is very different from coconut cream, and it is sometimes referred to as coconut butter. It consists entirely of dried coconut meat that has been ground very finely.
What is meant by coconut cream?

Moisture affecting the autoxidation of fats

Autoxidation starts with the formation of hydroperoxides catalyzed by traces of metals, particularly copper and by haematin compounds and is accelerated by light, heat and radiation of various types.

The process of autoxidation and the resulting determination in flavor of fats and fatty foods are often described by the term rancidity.

Moisture appears to prevent or inhibit fat autoxidation, perhaps by inhibiting the absorption of oxygen.

In the preparation of dehydrated foods, it has been observed that moisture levels of optimal stability vary with the type of product.  These levels range from 6% moisture for starchy foods to trace moisture for high –sugar-foods.

The protective effect of moisture is thought to occur by decreasing the catalytic activity of trace metals, by quenching free radicals and y promoting non-enzymatic browning, which produces compounds with antioxidant activities.

When moisture content is higher than the value at the monolayer, the solvent and mobilization properties of water become more important and the catalyst present are more easily mobilized and possible swelling of solid matrix exposes new catalytic site, making oxidation rates even higher.
Moisture affecting the autoxidation of fats

Temperature affecting autoxidation of fats

Temperature also has a marked effect on the rate of autoxidation. Generally, the autoxidation rate increases as the temperature is increased.

At the ordinary temperatures, the effect if increasing on the rate of autoxidation is slightly greater than for chemical reactions because increasing temperatures accelerates both the chain propagation reactions and peroxide decompositions. Low temperature storage helps to minimize temperature-induced oxidation.

The solubility of oxygen in an oil decreases with an increase in temperature therefore the effect of oxygen concentration on the rate of oxidation becomes less evident.

For example, by cooling the milk for some times before its use (at least 2 hours at 5 C), a part of the copper on the fat globules moves to the plasma; this may restricted the autoxidation. Moreover, the cooling causes a migration of protein to the plasma, and this precisely the protein that liberates H2S during heat treatment.
Temperature affecting autoxidation of fats

Heart disease and food

Some foods are found to increase the risk of coronary heart disease, while others may protect against it.

High blood total cholesterol and low density lipoproteins (LDL) cholesterol levels are major modifiable risk factors in the development of heart disease.

One group of fats have emerged as a major cause of cell damage leading to diabetes, a heart disease, cancer and many other conditions and these are trans fats. People with diabetes have a higher risk of heart disease and stroke.

Trans fats are found in almost every baked product, to prolong shelf life including potato chips, donut, and most popular breakfast cereals.

In epidemiological studies, fruits and vegetables has been an associated with decreased mortality from a variety of health outcomes including obesity, hypertension, metabolic syndrome and cardiovascular disease.

Higher consumption of fruits and vegetables has been associated with a lower risk of coronary heart disease.

In the early 1970s scientists found that Greenland Eskimos has extremely low incidence of heart disease and arthritis despite the fact that they consumed a high fat diet.

Scientists discovered that Greenland Eskimos consumption of omega 3 fatty acids play a crucial role in the prevention of atherosclerosis, heart attack, depression, and cancer.

Scientist research found that monounsaturated fatty acids (such as in olive oil), polyunsaturated fatty acids (such as in vegetables oils) and omega 3 fatty acids (such as in fish) may help lower blood lipids.

Diets high in soluble fiber such as in oat or rice bran, oat meal, legumes, barley, citrus fruits and strawberries may help lower LDL cholesterol.

The scientific evidence establishes that diets low in saturated fat and cholesterol are associated with decreased levels of blood total cholesterol and LDL cholesterol and thus decreased risk of developing coronary heart disease.
Heart disease and food 

Chemical properties of coconut oil

Coconuts, form the Cocas nucifera lam, are dehusked before cracking the nut to drain away the coconut water.  Coconut palm is productively gown within 20° north and south of the equator, especially along coastal areas.

Traditionally, coconut oil is extracted from copra by crushing in an expeller, followed by solvent extraction to recover the residual oil from the cake.

The oil content ranges from 34 to 45 % in the ripe endosperm of coconut and from 60 to 77 per cent in well dried copra.

The oil content is influenced by the water content in the nut, stage of maturity and the type of coconut variety.

The oil contains predominantly triglycerides with 86.5% saturated fatty acids. This makes the crude oil very stable against oxidation. They consist of C12, C14 and C16 with C12 predominating.

Others are 5.8% monounsaturated fatty acids, and 1.8% polyunsaturated fatty acids.

Of the saturated fatty acids, coconut oil is primarily 44.6% lauric acid, 16.8% myristic acid and 8.2% palmitic acid, although it contains seven different saturated fatty acids in total. Its only monounsaturated fatty acid is oleic acid while its only polyunsaturated fatty acid is linoleic acid.

Coconut oil is composed of a special group of fat molecules known as medium chain fatty acids (MCFA) which contains 8 to 12 carbon chains.  The sum of MFCA in coconut oil is 62%, which makes the oil the richest source of MCFA among vegetable oil.

Medium –chain fatty acids in coconut oil are broken down and used predominantly for energy production and thus seldom end up as body fat or as deposit in arteries or anywhere else.
Chemical properties of coconut oil

The importance of fats in human body

Fat is the name given to a broad category of substances we get from our food or make in our bodies. It is an essential nutrient, which contributes approximately 30-45% of food energy in western diets.

In technical they are referred to as lipids. Fat along with proteins and carbohydrates, one of the three nutrients are used as energy sources by the body.

Energy is one of the principal nutritional requirements of man and fat is a principal source of the energy. Each grams of fat consumed supplies the body with 9 calories worth of energy.

Total fat: the sum of saturated, monounsaturated and polyunsaturated fats. Cholesterol is from another lipid family called sterols.

Intake of monounsaturated and polyunsaturated fats can help reduce blood cholesterol when substituted for saturated fats in the diet.

In chemistry, a compound formed from chemicals called fatty acids. These fats are greasy, solid materials found in animal tissues and in some plants.

For most part, human did not require fat sources in their diets because the body can synthesize most of the fatty acids it needs from other constituents, including carbohydrate and protein.

The brain needs saturated fats, polyunsaturated fat, cholesterol, and a number of other fats. Fats are also a component of cell membranes, vitamin D and sex hormones.

Some types of fats give cell membranes flexibility and help regulate the transfer of nutrients into and out of cells, while others serve as precursors to vitamin D and sex hormones, such as estrogen and testosterone. 

Most saturated fats come from animal products. Unsaturated fats are prominent in both animal and vegetable foods.

The importance of dietary fat is underscored by the fat that 35% of the weight gain of an infant in early is accounted for by fat. Most of the dietary fat is in the form of triglyceride formed by the three fatty acids esterified to a glycerol backbone.

The role of fat in the diet is both physiological and psychological. In its psychological aspect, it is important to appearance and taste of foods.
The importance of fats in human body

Digestion and absorption of fat during infant stage

Newborn are limited in their ability to digest and absorb certain nutrients due to decreased activity of specific enzymes and other substances as well as functional and anatomic limitations.

The complex process of digestion/absorption can be optimally effective only when the GI tract and accessory organs are totally develop and fully functioning.

The gastrointestinal (GI) system is a complex organ system that extends from the mouth to the anus and includes the esophagus, stomach, small and large intestines, liver, and pancreas.

Not only must the muscular tube (alimentary canal) with it a mucosal lining and endocrine cells be operating efficiently in conjunction with the nervous system, but the accessory organs (pancreas, liver, and gallbladder) with their important digestive secretions also must be physiologically mature.

The secretion of gastric, intestinal and pancreatic digestive enzymes is not developed to adult levels in young infants.

Nevertheless, the infant is able to digest and absorb the nutrients in human milk fully and efficiently and breast milk contains enzymes that contribute to the hydrolysis of fat, carbohydrate and protein in the gut. 

Good examples of the emphasis on GI tract maturity are the care given to the fat in infant formula and the time and sequence of the introduction of various foods into the infant’s diet.

The infant pancreas, although structurally mature at term, is usable for several months to produce enzymes sufficient for effective digestion.

Pancreatic lipase, alpha-amylase and the proteolytic enzymes are in too short supply to accommodate digestion of a mixed diet. Digestion of fat is a real concern due to decreased levels of bile salts from the liver as well as low lipase release from the pancreas.

Bile salt low because of decreased syntheses and decreased intestinal reabsorption. While fetal lipase levels are detected at 21 weeks gestation, but do not reach adult concentrations until 6 months of age in the term infant.
Digestion and absorption of fat during infant stage

Fat changes in human body with increasing age

Fat mass is the most variable component of body composition. Changes in body fat concern and distribution occur with aging.

The nonfat component of the body is termed lean body mass. Body composition, primarily the composition of bone, fat and muscle, also change both absolutely and relatively with increasing age.

Infants average about 10% to 15% fat at birth. This increases to about 30% by 6 months of age and then begins to gradually decline during early childhood.

Percent body fat decreases to age 5, when it reaches 15% for boys and 17% for girls.

From ages 10 to 18 years percent body fat changes little in girls but decreases by about 1 % per year for boys.

The percentage of fat content of the body increases with increasing adult age, and the extent of increase varies among individuals within a population and among different populations.

Those who continue as athletes into advanced ages have a smaller increase in body fat content, but even in these people, some increase does occur.

A high percentage of body fat may be associated with established chronic disease risk factors such as elevated serum cholesterol and triglycerides, glucose and blood pressure.

Fat changes in human body with increasing age

Phospholipids in food

Phospholipids occur naturally throughout the plant and animal world, but in much smaller amount than triglycerides.

They are most abundant in egg yolks, liver, soybeans, wheat germs and peanuts.

Phospholipids may be removed by separation of two phases; from example, if butter is melted and filters, the pure oil thus obtained is free from phospholipids.

After refining of oils, neutralization, bleaching, and deodorization, the phospholipids content is reduced to vitally zero.

The amount of phospholipids associated with the glycerides of seeds is usually small, and expression, purification and refining of the oil remove most of this amount.

The phospholipids removed from soybean oil are used as emulsifiers in certain foods, such as chocolate.

Other favorable functions of phospholipids including ingredients for food, cosmetics, agriculture and pharmaceuticals.

Soybean phospholipids contain about 35 percent lecithin and 65 percent cephalin.

The fatty acids composition of phospholipids is usually different from what that of the oil in which they are present. The fatty acids make the phospholipids soluble in fat; the phosphate group enables them to dissolve in water.

The acyl groups are usually more saturated than those of the triglycerides.

Phospholipids of many vegetables oils contain two oleic acid residues.

The phospholipids of milk do not contain the short chain fatty acids found in milk fat triglycerides and they contain more long chain polyunsaturated fatty acids than the triglycerides.

The fat globules of milk are each surrounded by a thin protective layer, usually called a milk fat globule membrane.

This membrane is comprised of three major phospholipids species – sphingomyelin. phosphatidyl choline and phosphatidyl ethanolamine.
Phospholipids in food