Classification of carbohydrates

The word ‘carbohydrate’ was coined more than 100 years ago to disrobe a large group of compounds of the general formula Cn(H2O)n. Sugars, starches and fiber are the main forms in which carbohydrates occurs in food.

Carbohydrates can be classified based on their chemical structure and/or based on their physiological effects.  The classification of carbohydrate is a complicated subject due to in part to the numerous classification schemes or systems used in the past.

There are three main groups, monosaccharide, or simple sugars; oligosaccharides, of which the most prevalent in nature are the disaccharides; and polysaccharides the most complex of the carbohydrates.

All carbohydrates must be reduced to simple sugars (monosaccharides in the intestine before they can be absorbed into the bloodstream).

The most basic or simple form of carbohydrate is the monosaccharide. Typical monosaccharide are of the empirical formula (CH2O)n where n is a value between 3 and 9. The basic or archetypal monosaccharide is the six-carbon simple carbohydrate glucose. Glucose, a simple sugar, is the form in which carbohydrates circulate in the bloodstream.

Polysaccharides are large polymers of monosaccharides. Polysaccharides may consist of straight chains or branched chains having hundreds or ten thousands of monosaccharides joined together through glycosidic bonds.
Classification of carbohydrates

Fibers in food

Dietary fiber includes the nondigestible carbohydrates. The major portion of dietary fiber in foods is derived from the plant cell walls in foods. These may be either water soluble or water insoluble. Soluble dietary fiber tends to dissolve or swell in water while insoluble dietary fiber remains relatively unchanged.

Gel-forming soluble fibers are readily broken down by bacteria residing in the colon, as opposed to insoluble fibers, which are largely non-fermentable. Both have nutritional significance.

The water insoluble group such as cellulose and hemicellulose are found in the outer layers of whole grains, the strings of celery, the hulls of seeds and the skins of corn kernels. These fibers retain their structure and rough texture even after hours of cooking.

The water-soluble fibers such as those found in the brans of some cereals (e.g., oats and rice) and in pectin are believed to lower the levels of serum cholesterol by binding with bile acids and causing removal of cholesterol in the feces.

Dietary fiber exerts a wide range of physiological effects when consumed, and its complex nature is responsible for a range of physical and chemical properties that are responsible for these physiological effects.

Dietary fibers are now accepted to an important ingredient of a healthy diet, and are thought to reduce the probability of cancer induction in the digestive organs.

Dietary fibers shorten the time food remains in the digestive organs, and as a result a carcinogen will remain in contact with these organs for a shorter period.

The consumptions of fiber is recommended, although not to excess. It appears that excessive amounts of dietary fiber may interfere with the retention of minerals required by the body.
Fibers in food

Food minerals: classification and functions

Most foods contain mineral.  When burned, they leave a residue – a gray or whitish ash. Minerals are heat stable and classified into:
Main elements
Trace elements
Ultra trace elements

The main elements or major minerals include Na, K, Ca, Mg, Cl, P are essential for human beings in amounts >50 mg/day. Sulfur also belongs to this group.

Trace elements include Fe, I, F, Zn, Se, Cu, Mn, Cr, Mo, Co, and Ni are essential in concentrations of <50 mg/day: their biochemical actions have been elucidated

Although trace minerals are present in minute amounts, they play very important roles in the diet, and modern analytical methods are extremely sensitive to accurately measure them in foods.

Ultra – trace element (Al, As, Ba, Bi, B, Br, Cd, Cs, Ge, Hg, Li, Pb, Rb, Sb, Si, Sm, Sn, Sr, TI, Ti, W) are elements whose essentially has been tested in animal experiments over several generations and deficiency symptoms have been found these extreme conditions.

Minerals elements are used by the body in a great variety of ways. They may present in the cell fluids (potassium is particularly important) or like sodium, in extracellular fluids. Main and trace elements have very varied functions, e.g., as electrolytes, as enzymes constituents and a building materials, e.g., in bones and teeth.

The importance of minerals as food ingredients depends not only on their nutritional and physiological roles. They contribute to food flavor, texture and when digested provide the cofactors for enzymes that assists digestion.

Minerals are also responsible for food spoilage while in storage and must be viewed in the context of shelf life and food safety.
Food minerals: classification and functions

What are vitamins?

Vitamins have been defined as organic substances present in minute amounts in natural foodstuffs that are essential to normal metabolism and lack of which in the diet causes deficiency diseases.

Vitamins are required in trace amounts in the diet for health, growth and reproduction.

As the chemical structure of the vitamin became known through its isolation and synthesis; it was given a chemical name. When the chemical name was assigned, it was assumed that the name applied to one substance with one specific activity.

Some of the vitamins occur in foods in a form known as precursors or provitamin. Once inside the body, these are transformed chemically to one or more active vitamin forms.

Now it is evident that a vitamin may have a variety of functions and that vitamin activity may be found in several closely related compounds known as vitamers. An excellent example of this is vitamin A, which has several seemly unrelated functions and encompasses not only retinol but also retinal and retinoic acid.

The vitamins can further classified into two classes: fat soluble and water soluble. Soluble confers vitamin many of their characteristics. It determines how they are absorbed into and transported by the bloodstream.

The fat soluble vitamins are represented by vitamins A, D, E, and K absorbed and transported by conventional lipid transport.

For water-soluble vitamins, respective solubility coefficients are major factors that dictate the availability and ease of absorption.
What are vitamins?

Fatty acids – the simplest of lipids

Fats or lipids consists of numerous chemical compounds, including monoglycerides, diglycerides, triglycerides, phosphatides, cerebrosides, sterols, terpenes, fatty alcohols,  and fatty acids.

The fatty acids, the simplest of the lipids, are defined as monocarboxylic acids that tend to be more soluble in organic solvents than in water. They are a hydrocarbon with a methyl group at one end and carboxyl group at the other.

Some naturally occurring saturated fatty acids:
Butyric
Caproic
Caprylic
Capric
Lauric
Myristic
Palmitic
Stearic
Arachidic
Behedic
Lignoceric

The human body needs fatty acids and it can make all but two of them –linoleic acid (the 18-carbon omega-6 fatty acid) and linolenic acid (the 18 carbon omega-3 fatty acid).

Fatty acids are classified according to the number of double bonds they possess. It can be saturated, monounsaturated or polyunsaturated and are essential for energetic, metabolic and structural activities.

Some naturally occurring unsaturated fatty acids:
Monoenoic: Palmitoleic, Oleic
Dienoic: Linoleic
Trienoic: Linolenic
Tetraenoic: Arachidonic

Palmitic acid and stearic acid are by far the most commonly occurring and widely distributed of the saturated fatty acids whereas oleic acid and linolenic acid are the most prevalent of the unsaturated.

These four fatty acids account for over 90% of the fatty acids in the average American diet. Fatty acids of shorter chain length are for the most part minor constituents of plants and animal fats.

However, butyric acid and myristic acid occur in milk fat in large amounts and about 60% of the fatty acid in coconut oil consists of lauric acid and fatty acids of shorter chain length.

Highly unsaturated fatty acids are essential for cellular functions of many differentiated tissues in humans of all ages.

They are mostly incorporated in membrane phospholipids and serve as a structural component of the phospholipid membranes in tissues throughout the body.
Fatty acids – the simplest of lipids

General classification of lipids

Lipids are materials that are sparingly soluble or insoluble in water, but soluble in selected organic solvents such as benzene, chloroform, diethyl ether, hexane and methanol.

Although lipids a wide variety of structures, they possess a number of common features, which may be used in classifying them.

The following classification is limited to lipids of importance in animal nutrition and excludes the fat soluble vitamins that, although properly classified as lipids, following the classic practice of nutritionist.

A. Simple Lipids
Fatty acids
Neutral fats (mono-, di- and triacyl glycerols)
Wax
*Sterol ester
*Nonsterol ester

B. Compound Lipids 
Compound lipids are subdivided into two groups:
Phospholipids 
*Phosphatidic acids, lecithin, cephalins, etc
*Plasmalogens
*Sphinghomyelins

Glycolipid (carbohydrate containing)

Lipoproteins (lipids in combination with protein)

C. Derived Lipids, alcohol (including sterols and hydrocarbons)
General classification of lipids