Bacteria in Food

Bacteria make up the largest group of microorganisms and therefore, we will deal the same in details. People often think of them only as germs and the harm they do. Actually, only a small number of bacterial genera are pathogenic (disease causing). Most are harmless and many are beneficial. The bacteria and fungi are most important in relation to food. The most important genera of bacteria known to occur in foods are listed below in alphabetical order:

Acetobacter, Acinetobacter, Aeromonas, Alcaligenes, Alteromonas, Bacillus, Brochothrix, Campylobacter, Citrobacter, Clostridium, Corynebacterium, Entereobacter, Erwinia, Escherichia, Flavobacterium, Lactobacillus, Leuconostoc, Micrococcus, Moraxella, Pediococcus, Proteus, Pseudomonas, Salmonella, Serratta, Shigella, Staphylococcus, Streptococcus, Vibrio and Yersinia.

Some of these are highly desirable in certain foods, while others bring about spoilage or cause food poisoning gastroenteritis in humans. One-third of bacteria causing food poisoning belongs to the family Enterobacteriaceae.

Shapes and Arrangement of Bacteria

There are thousands of different kinds of bacteria. Some differ only slightly and it takes a highly trained person and a number of biochemical tests to identify them. There are also groups, which differ greatly in growth habits and appearance (morphology), and are quite easily identified. But regardless of minor differences, most bacteria can be classified into five basic cell shapes namely cocci (roundshaped), rods (elongated) spirochete (spiral), vibrio (comma-shaped) and filament bacteria (branched). In addition to their different shapes, their cell arrangement also varies. For example, some round-shaped bacteria (cocci) are always grouped in pairs (diplococci), some in chains (streptococci) and some in the form of bunch of grapes (staphylococci). Diplococci are the kind that causes pneumonia. Streptococci are often associated with 'sore throat'. Staphylococci are familiar to many because of their role in infections causing 'pus formation' and some types of 'food poisoning'. Bacteria also vary somewhat in size, but average about 1125,000 inch. In other words, 25,000 bacteria laid side by side would occupy only one inch of space. One cubic inch is big enough to hold nine trillion average size bacteria.

Bacterial Cell Shapes and Arrangements

The replication of bacteria

Bacteria reproduce by a process called 'binary fission', one cell divides and becomes two. Some can reproduce at a very rapid rate under proper conditions. If food and moisture are adequate and the temperature is right, certain bacteria can reproduce within as little as 20 minutes. Within 20 minutes, one cell becomes two and in 40 minutes, there will be four, and so on. In only eight hours, the original cell will have multiplied to nearly 17 million new bacteria. Of course, conditjons don't remain favourable for such a rate of reproduction for long. If they did, we could be burikd in bacterial cells.

Binary Fission

We must use a microscope capable of magnifying 500 times in order to see a single bacterial cell. However, if that cell is allowed to grow on suitable food or solid media, it will reproduce rapidly into a colony consisting of millions of cells. The colony is visible to the naked eye. Plate counting, a technique which makes it possible to determine the number of bacteria (colonies of bacteria grown from single cells) in a food sample without the aid of a microscope. An important thing to consider in the growth ofbacteria is the ability of certain types to produce spores. A 'spore' is a dormant or resting state of a bacterial cell. There are certain basic differences between the spores and the active or vegetative bacterial cells. The spores develop inside vegetative cells at the central, subterminal or terminal (at pole) positions with or without bulging of the cells. Generally, these spores are formed only when environmental conditions are unfavorable for growth. Subsequently, these may be released in the environment as free cells. Spores are not easily killed. In fact, conditions that will quickly kill active bacteria have little or no effect on spores. A temperature of 72OC (pasteurization temperature) will kill bacterial cells within minutes, but bacterial spores can resist this temperature indefinitely. This is important to us since in all processing times for canned foods are calculated by using both the time and temperature required to kill bacterial spores. Bacterial genera producing spores are Clostridiurn and Bacillus.

Bacterial Spores

Environmental and nutritive requirements of bacteria

We know that the availability of oxygen is essential for survival of human beings and animals. However, in case of bacteria, the requirement of oxygen for growth varies greatly. Accordingly, bacteria may be placed into one of the three groups.

The 'aerobic' bacteria thrive in the presence of oxygen and require it for their continued growth and existence. Other bacteria are 'anaerobic' and cannot tolerate gaseous oxygen. such as those bacteria that live in deep underwater sediments or some of those which cause bacterial food poisoning such as botulism. The third group is of 'facultative anaerobes', which prefer growing in the presence of oxygen, but can continue to grow without it.

Bacteria may also be classified on the basis of source of energy. There are two categories: 'heterotrophs' and 'autotrophs' . The 'heterotrophs' derive energy from the breakdown of complex organic compounds available from the environment. It includes 'saprobic or saprophytic' bacteria found in decaying material, as well as those that rely on fermentation or respiration. The other group is called 'autotrophs', which fix carbon-dioxide to make their own food source. They may be fueled by light energy (photoautotrophic) or by oxidation of nitrogen, sulfur, or other elements (chemoautotrophic).

Viewing of bacteria 

Bacteria under microscope can be viewed in a smear (a film) prepared directly from a little amount of food item or a bacterial colony grown on an artificial media. The bacterial cells can be viewed easily under microscope once the smear is stained with special colouring reagents called stains. The most commonly used stain is the Gram's stain. On staining the smear with Gram's stains, the circular forms (cocci) or elongated shapes (rods) of bacteria which take pinklred colour are called as Gram-negative bacteria, while the blue/violet coloured as Gram-positive bacteria.

Classification of bacteria

Depending upon their staining characteristics and shapes, bacteria have been classified into different broad groups (families), specific groups (genus) and closely related members within the groups (species).

A) Gram-positive bacteria

i) Cocci

The family Micrococcaceae includes two genera (singular-genus) of significance i.e., Micrococcus and Staphylococcus. Representative of both the genera can be isolated fiom wide range of foods, of these the micrococci are principally spoilers of salted foods. Members of the family Streptococcaceae are facultative anaerobes and form non-motile cocci that occur typically in chains or tetrads depending upon the method of cell division. Three genera, Streptococcus, Leuconostoc and Pediococcus are involved in food spoilage and the foods involved include bacon, vacuum-packed meats and milk.

ii) Endospore forming rods

The genus Bacillus consists of species that are aerobic and facultatively anaerobic. Bacillus species are very commonly isolated from both raw and cooked foods.

iii) Asporogenous rods

Lactobacillus is the remaining genus comprising 'lactic acid bacteria'. Lactobacilli are non-motile rods that often occur in chains and they are anaerobic or microaerophilic (require small amounts of oxygen for growth). They cause spoilage of variety of foods, but like streptococci, they are used as starter organisms in the food industry.

B) Gram- negative bacteria

i) Spiral and curved bacteria: Only one genus, Campylobacter is significant in foods, being important cause of food poisoning.

ii) Aerobic rods and cocci: Most important genus in this group is Pseudomonas. Many species of this genus grow at low temperature causing food spoilage. Several species produce insoluble yellow, orange or blue pigments but these are not important in foods.

The genera Acetobacter and Alcaligenes occur particularly in dairy products and eggs causing spoilage problems while, genus Brucella cause foodborne illness in man either by contact with animals or typically, by consumption of unpasteurized milk.

iii) Facultative anaerobic rods: These Gram-negative, rod-shaped bacteria grow either under aerobic or anaerobic conditions. Two distinct families are recognized. The first, Enterobacteriaceae, contains eight genera of interest, namely, Escherichia, Salmonella, Shigella, Enterobactel; Serratia, Proteus, firsinia and Erwinia. The second family, Vibrionaceae, contains only two genera of interest, Vibrio and Aeromonas.

All organisms in the family Enterobacteriaceae are either motile with peritrichous flagella or non-motile. There is only one species E. coli, in the genus Escherichia.

It is important as an indicator of faecal pollution but many strains can cause food poisoning.

The members of genus Salmonella in the form of more than 2500 different serotypes are very important cause of food poisoning. The members of Shigella species are fairly related to salmonellae except that the former are non-motile and the latter are predominantly motile. Both genera are primarily associated with man and vertebrates, and Shigella organisms are again pathogenic to man causing food-borne infections.

Yersinia species is of no great significance in foods, but one species enterocolitica, is now recognized as a cause of food poisoning in man. The remaining genera, Serratia, Proteus and Erwinia, are sometimes implicated in food spoilage. Only one species, S. marcescens, is included in Serratia and it is characteristically pigmented bright red. Proteus species are important in the spoilage of eggs and raw meats held at ambient temperatures whilest Erwinia species are involved in the spoilage of vegetables.

Family Vibrionaceae contains species that are typically motile with polar (at one end of the cell) flagella. Mbrio species is important in food since different strains cause food poisoning, food-borne infections and food spoilage while Aeromonas are sometimes involved in food spoilage as well as an important fish pathogen.

Genus Flavobacteriurn comprises of yellow-pigmented species that are regularly found on fresh meats and fish. However, their growth tends to be overgrown by other bacteria during spoilage of these foods. It has been implicated in the spoilage of milk and milk products.

Types of microorganisms in Food

The numbers and types of microorganisms present in a food or food products are influenced by the following conditions :

• General environment from where the food was originally obtained 
• Microbiological quality of the food in its raw or unprocessed state 
• Sanitary conditions under which the product is handled and processed
• Adequacy of subsequent packaging, handling and storage conditions.

Important Microorganisms in Food

Let us study to know about the microorganisms. As the name indicates these are small living forms of life, which we cannot see with e naked eye. Microorganisms are the most ubiquitous in nature. Six major groups of microorganisms are generally recognized, namely bacteria, fungi, virus, algae, protozoa and rickettsia. Some people often confuse and almost always I misunderstand, their functions, but they are just as real and alive as you are. They eat, grow, reproduce and die.

Have you ever wondered just how small microorganisms really are? Molds can be seen with only slight magnification by the use of an ordinary magnifying glass. Yeasts must be viewed through a microscope that magnifies several hundred times. Bacteria can best be seen when studied with a more powerful microscope that enlarges 1,000 times. Bacteria, yeasts and molds can be found everywhere. Scientists have gathered them fiom clouds above mountaii~to ps and in the deepest parts of the ocean. They are present on animals, human beings and even in the air we breathe. Microorpallisms have a direct impact on our daily lives. Some are helpful. They aid our bodily processes by helping break down complex foods into simpler substances. Some, called germs, are harmful to us by the role they play in causing diseases.

Lipid Disorders

Lipids are required in the body for different structural and functional activities. A dietary lipid deficiency may alterlaffect these functions to varying extent.

Hypovitaminosis

Lipids are essential for the absorption of fat-soluble vitamins, which may get affected in absence of sufficient fat. 

Ketosis

A special condition occurs in the body when the liver catabolizes excessive amounts of fatty acids in the absence or scarcity of carbohydrates. This condition is called "ketosis" and is observed:

• When glycogen stores are depleted, stored body fats becomes the chief energy source as in case of starvation
• When high fat and low carbohydrate diet is consumed
• In untreated diabetes mellitus.

In ketosis, liver gets flooded with fatty acids coming from diet or stored fat and produces compounds called ketones. These compounds cannot be oxidized by the liver and are then put in the blood. As the blood ketone levels go up, they are excreted in the urine. This statelcondition is called ketonuria. The symptoms of ketosis include greater urine volume than usual, depressed appetite, nausea, excessive tiredness, dizziness, and bad breath. Prolonged elevation of blood ketones (which are acids) is dangerous as it causes the blood to become acidic resulting eventually in death. Ketosis disappears when carbohydrates are consumed and utilized by the body. 

Coronary Heart Diseases (CHD)

Excess fat intake relates to the prevalence of diseases such as obesity, heart diseases and cancer. Most people require at least 15 to 20 per cent of the kilocalories as fat to provide a palatable diet with sufficient satiety value. Coronary heart disease refers to damage to the heart muscle due to inadequate blood supply from the coronary arteries. Fat deposition takes place in the arteries in the form of plaques and this condition is called atherosclerosis. Plaques contain cholesterol, phospholipids, triglycerides, connective tissue and fibrin. Formation of plaques narrow the blood vessel lumen through which blood flows. Platelets, a type of blood cells, also adhere to the rough surface of plaques. These changes in the blood vessels decrease blood flow and a condition called myocardial infarction (heart attack) may develop, which could be fatal. Many factors'including fat rich diet have been implicated as possible causes of CHD. Adiet low in fat is advisable to prevent such disorders.

i) Dietary fat and cancer: Dietary fat has been linked to cancer based on epidemiological data. Countries with high fat intake have high death rate due to cancer of colon, breast whereas those with low fat consumption have low incidence of cancer.

Effects of higher intake of dietary Fat, Carbohydrates and Proteins

ii) Nicemenn-Pick disease: There are some inherited lipid disorders that needs attention. There is a balance between lipid synthesis and breakdown. The breakdown is initiated by hydrolytic enzymes in the lysosomes (an organelle inside the cell). When breakdown of sphingolipid is altered due to a defect in hydrolytic enzyme, partial breakdown products of this lipid accumulate in the tissues. In Niemann-Pick disease, sphingomyelin accumulates in brain, spleen and liver causing mental retardation and early death.

iii) Tay Sachs disease: In Tay-Sachs disease, ganglioside accumulates in the brain and spleen due to enzyme deficiency. The symptoms of this disease are progressive retardation in development, paralysis, blindness and childhood death. These disorders can now be diagnosed and averted at a very early

stage during pregnancy by genetic counselling.

Lipids of Biological Importance

Fatty Acids

These are the building blocks of most lipids. They are long chain organic acids having 4 to 24 carbon atoms. They have a single carboxyl (COOH) group and a long non-polar hydrocarbon tail, which makes it non-polar (water insoluble) and greasy in nature. Fatty acids do not occur in free form in cells but are bound tightly in different types of other lipids. Fatty acids are of many types. They vary in chain length and also differ in the presence, number and positions of their double bonds (Table). Saturated fatty acids are those that do not possess any double bonds in hydrocarbon tail. Their general formula is CH,-(CH,)n-COOH. Unsaturated fatty acids on the other hand have one or more double bonds. Natural fatty acids have even number of carbon atoms.

Triglycerides

These are fatty acid esters of glycerol and are most abundant lipids, also often referred as fats. Oils also come in the same category but the only difference in fat and oil is that, at room temperature fat is solid whereas oil is liquid. More or less all animal lipid is fat. A triglyceride has a glycerol with three fatty acids attached to it. Triglycerides act as storage fat in plant and animal cells. In eukaryotic cells, triglycerides form microscopic droplets, which act as energy storehouse. Specialized cells called adipocytes or fat cells store large amounts of triglycerides that almost occupy the cell interior. Why triglycerides are preferred as storage fuel rather than carbohydrates such as starch or glycogen? There are two reasons for this: first, being hydrophobic, triglycerides do not carry extra weight of water which carbohydrates, being hydrophilic, do carry and are not advantageous to the cell. Second, carbon atoms of triglycerides are more reduced (more hydrogen atoms attached) than the carbon atoms of sugars and this gives twice the amount of energy per gram on oxidation than carbohydrates.

Triglycerides stored under the skin also serve as an insulator against low temperatures. Seals, walruses, penguins and many other warm-blooded animals are well padded with triglycerides. In hibernating animals, triglyceride serves both as an energy source as well as an insulator.

Fatty acids attached in triglycerides could be same or different. Triglycerides with unsaturated fatty acids are liquid at room temperature. Such triglycerides are converted into solid fat by adding hydrogen to the double bond of their fatty acids. This process is used in the manufacturing of hydrogenated fats commonly called as "DALDA". Oxidation (addition of oxygen) of triglycerides by air results in rancid fat, which is off-taste and has awful smell. In body, vitamin E, vitamin C and other reducing substances prevent oxidation of fat.

Waxes

These are fatty acid esters of long chain alcohols with 16 to 22 carbon atoms. Fatty acids in waxes may be saturated or unsaturated and contain 14 to 36 carbon atoms. Skin, hair, wool and fur have waxes, which serve as a protective covering and are secreted by skin glands. Waxes are the chief storage form of metabolic fuel in plankton, a free-floating marine microorganism. Waxes also have pharmaceutical and other uses in industries such as ointments, lotions and polishes.

Phospholipids

Biological membranes are rich in phospholipids. They have a highly polar (water loving) "head" group and a hydrophobic (water repelling) hydrocarbon tail. These characteristics favour formation of biological membranes in a double/ bi layer structure with semi-permeable property. As the name implies, these lipids contain phosphorous and are structural components of biological membranes. A phospholipid contains a glycerol with two fatty acids attached to carbon one, two and a phosphate bounded to third carton in the form of phosphoric acid to which a second alcohol is attached. Different phospholipids differ in their head group alcohol. Within the same phospholipid class, say phosphatidylcholine (a choline containing phospholipid), there may exist a number of molecular species differing in fatty acid composition.

In some phospholipids, one of the fatty acids is attached to glycerol in ether, rather than ester linkage. These lipids are called plasmalogens and are present in vertebrate heart tissue and constitute about half of the phospholipid content. Plasmalogens are also present in the membrane of certain bacteria and some invertebrates. The function of plasmalogens is not precisely known. Platelet activating factor, a type of plasmalogen, released by basophils (a type of white blood cells) plays an important role in inflammation and allergic response.

Sphingolipids

These are present in membranes. They do not contain glycerol but possess a long-chain fatty acid and one long-chain amino alcohol called sphingosine and a polar alcohol. The three carbons of sphingosine are structurally analogous to the three carbons of glyceroi found in Phospholipids, nervous system is rich in sphingolipids. There are three types of sphingolipids differing in polar head groups: 

(a) Sphingomyelins: They contain phosphorylcholine or phosphorylethanolamine as the head group and are clubbed with phospholipids.

(b) Glycosphingolipids: As the name indicates they contain one or more sugars as head group. 

(c) Gangliosides: It contains complex sugars.

Sterols

They contain no fatty acids and are important component of membranes. They consist of four fused rings, three with six carbons and one with five. Cholesterol is the major sterol in animal tissues and has a polar hydroxyl group. Sterols serve as precursor for many compounds, for example, steroid hormones, which regulates gene expression; bile acids that facilitates fat digestion in the intestine.

Classification of Lipids

Lipids are not a polymer of repeating nonnumeric unit similar to polysaccharide or protein. Lipids are compound soluble in ether or benzene or in chloroform but only sparingly soluble in water. There are several basis of lipid classification such as their hydrolysis product.

Classification on the Basis of Chemical Nature

On the basis of chemical nature lipids are classified into four types.

i) Simple lipids: These are esters of fatty acids with various alcohol. Examples: Fats, oil and waxes.

Structure of Ester

ii) Compound lipids: These are esters of fatty acids containing groups in addition to an alcohol and fatty acids. Examples: Phospholipids, Glycolipids, Lipoproteins.

General structure of a compound lipid

iii) Derived lipids: These are derived from above mentioned phospholipids, glycolipids etc.

iv) Miscellaneous: It includes Sterol, Tapenes etc.

Another classification of fatty acids are: Essential fatty acids and Non-essential fatty acids. Non-essential fatty acids are those which body can synthesize itself or their inclusion in diet is not necessary whereas, essential fatty acids are those which have to be obligatorily included in diets and are able to cure the diseases caused by the diet deprived of essential fatty acids. The number of essential fatty acids are three. They are Linoleic, Linolenic and Arachidonic acid. The linoleic can be converted to linolenic and arachidonic acids and therefore, the presence of linoleic acid in diet can manage other two essential fatty acid.

Classification on the basis of Saponification

Classification of lipids on the basis of Saponification

Importance and Functions of Lipids

Some of the food items that are identified as lipids are oils, butter etc. Food items rich in lipids are eggs, meat, nuts and seeds. We need fat in diet to keep our body healthy and to perform body, vital functions.

Utility of Lipids in Biological System

Energy: A major function of fat is to supply an efficient fuel to all tissues except central nervous system and brain, which depends on glucose.

Thermal insulation: The body fat underneath the skin regulates/controls body temperature. 

Vital organ protection: A web-like padding of adipose fat surrounds many vital organs such as kidney, protecting them from mechanical shock and providing a supporting structure.

Nerve impulse transmission: Fat layer surrounding nerve fibers provide electrical insulation and transmit nerve impulses.

Tissue membrane structure: Major constituent of cell membrane structure, which is vital for transport of molecules across membrane.

Cell metabolism: Complexes of fat and protein called lipoproteins carry fat in the blood to all cells.

As precursor substances: Fatty acids and cholesterol are precursor for many important molecules involved in metabolic functions and tissue maintenance.

Emulsifier: Amphipathic lipids such as phosphoglycerides, bile acids act as emulsifiers in our body.

Hormonal and Vitaminogenic: Many of the hormones (sex hormones) and vitamins are of fatty nature. Synthesis of these hormones requires lipids.

Industrial Use of Lipids

Lubrication: Almost all machinery requires lubrication for which lipids is needed.

Cosmetics: Lipids are extensively used in this industry. Volatile lipids are used in perfumes, deodorant, soap etc.

Food flavor  Lipids in food is responsible for flavour and other attributes like juiciness, texture etc. You will learn more about this in other units.

Pharmaceuticals: Many of the drugs have lipid base given orally, through injection and applied topically, like synthetic hormones, steroids, ointment and lotion.

Absorbents: Lipids are used to absorb / adsorb colour also. For a better shining, we use polish on our shoes or any other articles, which has lipid base.

Miscellaneous

In addition to their role as energy source/reservoir and as the components of membranes, lipids derivatives do perform some other vital functions Phosphatidylinositol and its phosphorylated derivatives act as intracellular signals to regulate cell structure and metabolism.

Eicosanoids are paracrine hormones, substances that act only on cells near the point of synthesis. Eicosanoids are derived from arachidonic acid, a 20-carbon polyunsaturated fatty acid. There are three classes of eicosanoids: 

(a) Prostaglandins: They were first isolated from prostrate gland. They act on tissues by regulating intracellular messenger, cyclic AMP. Different prostaglandins perform different functions such as smooth muscle contraction, regulation of I blood flow and rise of body temperature causing pain and inflammation. 

(b) Thromboxanes: Produced by platelets and facilitates clot formation.

(c) Leukotrienes: These are observed in white blood cells and liming of the airway to the lungs. These induce muscle contraction. Overproduction of leukotrienes is responsible for asthamatic attacks.

Role of Eicosanoids in human

• Cardiac function
• Regulation of blood pressure
• Bronchial muscle contraction
• Role in inflammation
• Vascular contraction
• Platelet aggregation
• Gastric secretion
• Intestinal motility
• Renin release, sodium excretion
• Lipolysis
• Luteolysis,
• Uterine contraction.

Lipids

Lipids are chemically a distinct group of substances, which are water insoluble. Fats, oils and other greasy compounds that are part of our diet are included in lipids. The commonly used term for lipids is fat. Like carbohydrates and proteins, lipids also contain carbon, hydrogen and oxygen. However, the ratio (77: 12: 1 1 approximately) differs. In addition to carbohydrates, lipids are the other basic fuel source and are highly concentrated (9.2 Kcal/gm) and give about twice the energy value of carbohydrates. Some food items are extremely rich in lipids. Lipids perform various functions in the body. Primarily it acts as a stored form of energy besides being important component of cell membranes. There are many health disorders associated with lipids.

Applications of Enzymes

As mentioned earlier most enzymes are proteins and carry out different metabolic functions in the body. They have numerous applications. Some important ones are given below:

Role in Medicines

One of the important applications of enzymes is in disease diagnosis. Alterations in the blood levels of certain enzymes occur during diseased conditions and are listed in Table. Measuring the levels of these enzymes would tell us the health status of a person.

Enzymes of clinical importance

Enzymes also have applications in medical therapy. Streptokinase is an enzyme, which breaks down fibrinogen as well as plasminogen. Plasmin formed fiom the latter helps in dissolving clot. This enzyme is now used to dissolve blood clots in the body to prevent heart ailments.

Industrial Applications

In meat industry, enzymes are used for tenderization, a process that makes muscle tissue soft. Some of these enzymes are fiom plant sources: papain (papaya), ficin (fig), bromelein (pineapple). Bacterial and fungal enzymes are: hydrolase D, protease 15 and rhozyme. Details of tenderization are given else where in this course. In milk industry, rennet, an enzyme obtained from calf intestinal linings, is used for cheese preparation.

Protein Deficiency Diseases

You all studied earlier that protein constitutes the major portion of our body mass after water. There are a number of diseases related to protein metabolism and its deficiency in diet. For better understanding its better to deal deficiency diseases in correlation to functional importance of protein. The subject has been dealt here under different headings.

Protein Turnover

Tissue proteins are continuously being broken down into amino acids and are then rebuild into tissue proteins. This process is called protein turnover and varies in different tissues. High protein turnover is observed in the intestine (epithelium), liver, pancreas and kidney whereas; muscle, brain and skin have low. Structural tissues such as collagen and bone have very low turnover. Dietary deficiency of protein may lead to structural and functional alteration of these important body parts.

Protein Balance

Body proteins exist in two compartments: Tissue proteins and plasma proteins. Balance between the two compartments is maintained by dietary protein intake. There is a give and take relationship between the two compartments at times. During growth, the protein synthesis is higher so that the new tissues could be formed whereas during ageing, tissue breakdown exceeds that of synthesis and the body gradually deteriorates.

Criteria to assess a person's state of protein balance are the measurement of total nitrogen. Total body nitrogen includes, protein nitrogen and non-protein nitrogen represented by compounds such as urea, ammonia, uric acid etc. It is an indication of all nitrogen gains and losses in the body protein. A net negative nitrogen balance is not a healthy sign and reflects increased loss of body protein and low input of food protein. It is observed during long illness, starvation or hyper metabolism (higher body activity).

Protein Requirements

The primary purpose of protein in the diet is to supply amino acids in sufficient quantity for growth and tissue maintenance. There is an enhanced protein requirement during growth. Also important is the nature of protein in the diet and its amino acid composition. Sufficient non-protein foods in the diet are also essential so that proteins are not used up for energy production. This is called protein-sparing effect. The digestibility and absorbability of the protein is affected by cooking methods and other factors. The recommended amount of protein per day (RDA) amounts to about 60-65 gramsfday for a healthy man and 50 grams 1 day for a woman, which increases during pregnancy and lactation. The nutritive value of a food protein is often expressed in terms of its chemical score, a value reflecting its amino acid composition. The chemical score of aprotein is calculated by comparing its amino acid composition with that of egg protein, taken as a standard, having a value of 100. Other criteria that are also considered during the calculation of chemical score of a protein are:

• Biological value (BV) based on nitrogen balance.
• Net protein utilization (NPU) based on biological value and degree of digestibility
• Protein efficiency ratio (PER) based on weight gain of a growing test animal divided by its protein intake.

As we discussed in the protein function that it plays a vital role in the regulation of body process. Deficiency may lead to hormonal imbalance, poor immune status, anemia, wasting condition as well as impairment of several body processes because of lack of necessary enzymes.

Protein Calorie Malnutrition (PCM) 

Growing children require a higher amount of protein and energy (Kcal) per kilogram of body weight than adults. Breast milk usually provides these needs during infancy (first six months). After that, weaning foods adequate in calories, protein, vitamins and minerals need to be added to the breast milk diet for growth.

Protein calorie malnutrition (PCM), a nutritional deficiency, is prevalent among infants and small children particularly in underdeveloped poor countries. PCM is characterized by poor growth and is manifested in two forms: Marasmus, a chronic state with severe wasting of the body tissues and Kwashiorkor, in which edema occurs.

Marasmus is seen in young children (three months to three years) and kwashiorkor occurs in the age group of one to five years. Marasmus is due to low calorie low protein diet whereas kwashiorkor develops due to protein deficiency even though there are sufficient kilocalories in the diet.

Meat Proteins - Structure and Classification

Meat in true sense refers to the flesh of animals used as food. It includes muscles (musculature), organs such as liver, kidney, brains and other edible tissues. The term carcass is used in meat industry and represent the portion of body left after removal of the blood, head, feet, hides, internal organs (digestive tract, intestine, bladder, heart, trachea, lungs, kidneys, spleen etc.) and adhering fatty tissues.

Chemical and Biochemical Constituents of Muscle

The approximate composition of meat is: 75 per cent water, 19 per cent protein, 3.5 per cent of soluble non-protein substances and 2.5 per cent fat. It must be remembered that meat is the resultant product of a complicated postmortem changes of a tissue.

Chemical composition of a typical adult mammalian muscle

Muscle proteins can be broadly classified into three types depending on their solubility properties:

i) Sarcoplasmic proteins: These are readily extracted in aqueous solution of low ionic (0.15 or less) strength i.e., soluble in water or very dilute salt solutions. It constitutes about 5.5 per cent of total muscle mass. There are about 50 sarcoplasmic proteins. It includes myoglobin, hemoglobin, enzymes associated with glycolysis, the tricarboxylic acid cycle and the electron transport chain, flavour proteins.

ii) Myofibrillar proteins: These are soluble in concentrated salt solutions and require higher (0.3 or greater) ionic strength solutions of sodium or potassium salts for their extraction. Since they are extracted by salt solutions, they are called salt-soluble proteins. They constitute about 11.5 per cent of muscle mass. The myofibrillar proteins are hrther classified into three categories.

a) Contractile Proteins: Actin and myosin constitute the major contractile proteins. They are named so because of their role in muscle cot traction. Actin constitutes approximately 20 per cent of the myofibrillar proteins whereas myosin, fibrous in nature constitutes 45 per cent of the myofibrillar protein. Actin forms the thin filament whereas myosin forms thick filament. The monomeric unit for actin is globular actin or G action and it links to form fibrous actin or F actin. In F action, the G action monomers are linked together in strands, much like beads on a string of pearls. Super helix, a characteristic of actin filament is formed as result of spiral coiling of two strands of F actin around each other. As far as myosin is concerned, proteolytic enzyme degradation reflects two fractions - light meromyosin and heavy meromyosin. The structure 01 the myosin molecule is an elongated rod shape with a thickened portion at one end called head, thin backbone called tail and a connecting between two is neck. Myosin has six subunits (polypeptides): two heavy chains and four light chains. The heavy chains are extended and wrapped around each other in a coiled manner. Molecules of myosin aggregate in muscles to form thick filaments which act as the basic contractile unit.

b) Regulatory proteins: These are involved in regulation of actin-myosin interaction during muscle contraction and in maintenance of myofibril integrity. The chief regulatory proteins are tropomyosin, troponin. a-actinin and p-actinin. Tropomyosin is approximately five per cent ol myofibrillar protein and lies in close contact with actin filament Tropomysoin exerts inhibition on crossbridge formation between actir and myosin except during contraction. Troponin is another regulator protein, approximately five per cent of myofibrillar protein and also founc in close association to actin. It is responsible for picking up the Ca2- available in sarcoplasm because of action potential. The calcium bind to troponin and this calcium activated troponin relieve inhibition being exerted by tropomyosin to facilitate contraction. The other two protein a and p-actinin constitute approximately two per cent and one per cen respectively and found in Z disc and free end of thin filaments within r band.

c) Cytoskeleton protein: They serve as the template and / or provide th scaffold for the alignment of myofilaments during myofibril an sarcomere formation. In mature muscle, these are responsible for maintenance of overall longitudinal and lateral alignment as well as structural integrity of myofibrils. Cytoskeleton proteins includes titin, nebulin, C-protein, myomesin, M-protein, desmine, filamin, vinculin, synemin, 2-protein, creatinine kinase.

iii) Stromal protein: They are of fibrous nature and not soluble even in high ionic strength salt solutions. These are refered as insoluble protein fraction of muscle. As such in muscle fiber they are approximately two per cent but more in connective tissue. The major stromal proteins are collagen, elastin and reticulin. Collagen is the most abundant protein in  animal body, about 20-25 per cent of total body protein. The tropocollagen is the structural unit of collagen fibril. Collagen is a glycoprotein which is a most abundant amino acid and one third of collagen is glycine. The relative insolubility and high tensile strength of collagen fibers results from intermolecular cross-linkages which influence meat tenderness.

Elastin is rubbery protein present throughout the body in ligament and arterial walls. It comprises of high content (about 90 per cent) of nonpolar amino acids responsible for its extreme insolubility. Being resistant to digestive enzyme and cooking, it contributes little or nothing to nutritive value of meat. Reticulin is another stromal protein which gives black with ammonical silver. It is different from collagen in having intimate association with lipids containing myristic acid.

Proteins - Building Blocks, Types and Sources

Each protein is a collection of several amino acids and these amino acids are called building block of proteins. Depending upon these buildigg blocks, nature of the protein'varies. Building blocks, types and sources of different proteins are described below:

Building Blocks of Protein - Amino acids

There are 22 amino acids that usually makeuplform proteins. Amino acids are covalently linked in proteins in a linear fashion by a linkage called peptide bond.

A molecule of water is removed from two glycine amino acids to form a peptide bond

It is remarkable that though different proteins contain the same set of amino acids, they differ in their arrangement in linear chain to give rise to proteins with diverse functions such as enzymes, antibodies, hormones etc. As the name indicates, amino acids contain at least an amino and a carboxyl group. Based on their chemical properties, amino acids can be grouped into five classes: nonpolar, polar, aromatic, basic and acidic. However, on nutritional basis they are classified as essential amino acids and non-essential amino acids. There are eight amino acids that are grouped under essential amino acids. These are required in the diet because body cannot synthesize them. The remaining amino acids can be synthesized in the body and are therefore non-essential in the diet. However, this classification is ambiguous as all the 22 amino acids are necessary for building body's tissue proteins.

Classification of amino acids

Types of Proteins and their Sources

According to the nutritional requirements, proteins are classified as complete or incomplete. This classification is based on the amount of essential amino acids present in a protein. Complete proteins are those that contain all the essential amino acids in sufficient amount and ratio to meet the body's requirements. Proteins of animal origin such as those in egg, meat and milk are considered as complete proteins, whereas proteins derived from plant products such as grains and legumes are incomplete  proteins. Poultry, fish, meat, peanuts, wheat germ, cheese are most concentrated protein foods on weight basis. Milk has 3.0 - 3.5 per cent protein whereas cereals such as rice and oat meal and potatoes have only about 2.0 per cent protein. Vegetables and hits have low protein concentrations.

The nutritive value of plant proteins can be improved by complementation. By combining a plant source low in one amino acid with another supplying that amino acid, we can complement or mutually supplement proteins. Vegetarians should use a combination of complementary protein in their diet. For example, beans, peas are rich in lysine but low in sulphur containing amino acids such as methionine and cysteine which can be complemented by including cereals (wheat) in the diet.

Importance and Functions of Proteins

Proteins are major component of our body cell and play various important roles. Major functions of proteins are detailed out below:

a) Tissue building (growth) and maintenance: This is the main function of dietary proteins. Many proteins are involved in body tissue formation. For example, proteins myosin and actin contribute significantly to muscle structure. Collagen and keratin are other structural proteins.

b) Physiological role: Proteins play a vital role in functionary of body. Enzymes being biocatalyst in nature, are among the most important proteins in the body. They act as catalyst and increase the rate of chemical reactions in the body. Various hormones are of proteinous nature and similar to enzymes regulate metabolic reactions. Besides this, the breakdown product of protein i.e., amino acids, di-peptides, polypeptides are utilized for synthesis of much needed bio-compounds inside body. Tryptophan, an essential amino acid is used to build Niacin (Vitamin B,) and serotonin acts as neurotransmitter. Acid-base balance is important for all physiological activities and is maintained by the buffering action of the proteins. The pH of the blood is slightly alkaline (pH 7.3-7.4). A drastic alteration in blood pH would be fatal. The blood pH is maintained by the buffering actions of proteins, which can accepted release H'essential for pH maintenance. Besides this, blood pigment haemoglobin that helps in transport of gases posses a protein globulin portion. Several lipoproteins are also engaged in transportation work. Protein provides defense to body in the form of antibodies. These proteinous substances are also responsible for gene regulatory, detoxicating and hemostatic function in body. 

c) Energy source: Body does not use proteins as main source of energy. Protein rich foods are expensive. However, proteins can be used for energy requirements ddrhg fasting, long distance running but not in fed state. Protein is also utilized as reserve material for nutrition of developing cells. One gram of protein, releases 4.08 Kcal of energy. It is estimated that close to 58 per cent of dietaty protein may be used up for energy production.

Proteins

The word Protein is derived from greek word proteus, which means to come first. They are the most abundant biological macromolecules / substances present in all types of cells constituting the major components of our muscle mass. Nearly half of the dry weight of a typical animal cell is protein. All proteins contain carbon, hydrogen, oxygen and nitrogen. It also contain sulphur with occasional occurrence of phosphorus. Average composition of protein shows 50% of carbon, 7% of Hydrogen, 23% of Oxygen, 16% of Nitrogen, 0-3% of Sulpher and 0-3% of Phosphorus. Proteins are made up of small building blocks called amino acids. the amino acids chemical compounds that contain both an acidic carboxyl (-COOH) and a basic Amino (-NH2) group.

General structure of an amino acid

Different proteins have different sizes depending on the number of amino acids they contain. They represent molecules through which genetic information is expressed. 'Proteins perform diverse functions and are therefore important part of our diet. Some foods are rich in protein whereas some have low protein content.

Low protein diet results in many disorders that may impair our abilities to perform well. Some specialized proteins called enzymes perform chemical reactions in the body. Enzymes referred as bio catalyst also have industrial applications.

Dietary Fibers and their Importance

Dietary fibers are also known as crude fibers and these are made of polysachharide. Importance of dietary fibers in body physiology, specially in relation to consumption of meat is discussed below:

Carbohydrate Content of Meat

Meat provides calories from proteins, fats and limited quantities of carbohydrates. It's more vital contributions to diets are derived from protein, B vitamins, certain minerals and essential fatty acids. Carbohydrates constitute less than one per cent of the weight of meat, most of which is present as glycogen and lactic acid.

The liver is the main storage site of glycogen. Meats are poor source of carbohydrates except those processed products to which sugars or other carbohydrates have been added. The lack of carbohydrates content in meat and meat products induces constipation and particularly for old age group. Now-a-days the introduction of dietary fiber in diet and even in meat product fornlulation is being practiced. Besides reducing the cost, it has various added advantages because of its physiological properties. Some of the physiological properties of dietary fiber along with related effects in body system have been discussed below.

Physiological Properties of Fibers

Dietary fiber includes a variety of polysaccharides. About 15-20g /day of dietary fibers is recommended for health. Different physiological properties are:

Water absorption: Water absorption contributes to bulk forming laxative effect. It influences the transit time of food mass through the digestive tract and further absorption of nutrients.

Binding effects: Binding effect of fibers influences blood lipid levels through their capacity to bind cholesterol and bile salts and prevent their absorption. Excessive dietary fiber has undesirable effect of binding minerals such as iron, zinc or calcium thus preventing needed absorption.

Clinical Association Between Dietary Fiber and Various Diseases

Because of diverse physiological function dietary fibers are useful in various diseases. The effects of fibers in various diseases are listed below:

Use of dietary fibre during disease condition

Clinical Applications of Carbohydrates

you all learnt how much important is carbohydrate for our body. The carbohydrates should be supplied.to body in a continuous manner. Both excess as well as lack of carbohydrates is detrimental for body. There are a number of diseases associated with carbohydrates such as hypoglycemia, ladtose intolerance, diabetes mellitus, galactosemia, glycogen storage disease etc. Diseases associated with carbohydrate are given below.

Hypoglycemia

Hypoglycemia means low sugar level in blood.

Symptoms: Nervousness, anxiety, hunger, palpitations and headache.

Causes: Clinicians have identified two types of hypoglycemia and their causes.

i) Reactive hypoglycemia: Reactive hypoglycemia occurs after a meal if persons had abdominal surgery or has diabetes.

ii) Fasting hypoglycemia: Fasting hypoglycemia occurs due to inadequate food or from poor eating habits: Several drugs may cause hypoglycemia e.g., alcohol which blocks glucose productiori in the liver.

Other clinical conditions which cause hypoglycemia are: 

(i) Tumors in pancreas stimulate excessive insulin secretion 

(ii) Adrenal insufficiency: Stress conditions increases metabolic demands of the body and contribute to hypoglycemia which is due to adrenal insufficiency.

Diagnosis: Normal blood glucose range is 70 - 110 mg/100ml. Below 70mgl 100ml of blood sugar level is the sign of hypoglycemia.

Treatment: A diet of frequent small meals, rich in complex carbohydrates and a good dietary fiber content with fewer carbohydrates and sugars.

Lactose Intolerance

One of the most common problems throughout the world is lactose intolerance. In this condition, the man is unable to digest product with lactose such as nonferhented milk.

Symptoms: Abdominal cramps, nausea, bloating or diarrheoa when milk is consumed.

Cause: The problem is due to deficiency of lactase, a digestive enzyme found in - the microvilli of small intestine that converts milk sugar and lactose (by hydrolysis) into its component monosaccharide, glucose and galactose for absorption. Children are born with high level of lactase to utilize high lactose level in mother's milk. In animals, lactase activity decreases shortly after birth

and in human after five years of age.

Diagnosis: Based on symptoms along with history of non-fermented milk consumption.

Treatment: Treatment consists simply cutting down of milk consumption. Most lactose intolerant patients digest fermented milk products (cheese, butter milk, yogurt) very well and they can consume these as their primary source of calcium instead of milk. Low lactose milk and sweet acidophilus milk have been

developed for lactose intolerant people.

Diabetes Mellitus

It is a metabolic disorder in which the ability to oxidize the primary fuel glucose is almost lost. It also affects the fat and protein metabolism.

Normal Pbysiological Functions of Pancreas

Symptoms: Glucose level increases in the blood and is lost in the urine, causing excessive urination, thirst and hunger and on prolonged disease develops multiple system complications.

Cause: Sugar and other simple carbohydrates can contribute to blood glucose level in persons with diabetes. Sugar does not cause diabetes but the cause is due to lack of available insulin, the pancreatic hormone.

Diagnosis: Diagnosis of diabetes can be done by different methods like:

i) Estimation of sugar in urine (Glycosuria): Presence of sugar in urine is dctected by colorimetric method.

ii) Elevation of blood sugar (Hyperglycemia): Normal level of blood sugar is 70 - 100 mg/100ml. In diabetes, blood sugar level increases from the normal level.

iii) Glucose tolerance test: In this test, 75 gram dose of glucose is given to patients. The patient is kept on fasting and two hour plasma was collected.

The glucose level is estimated. A two hour plasma glucose value of 200mgl lOOml or above indicates diabetes and 140 - 200mg/100ml indicates the impaired glucose tolerance.

iv) Glycosylated Hemoglobin Alc: It is a relatively stable molecuie within the red blood cells. Higher the level of circulating glucose over the life of the red blood cells, the higher the concentration of glycohemoglobin. It provides an effective tool for evaluating long-term management of diabetes and degree of control.

Treatment and control: Treatment of diabetes includes:

Well-planned food habits and exercise

Insulin therapy

Self-monitoring of blood glucose level

Nutrient balance: Ratio of carbohydrate, protein and fat in the diet is based on the recommendation of ideal glucose regulation. Majority of carbohydrate in the form of complex carbohydrate, starch should be used. About 50 - 55 per cent of total kilocalorie of the diet is of complex carbohydrates. It gives simple sugars slowly over a time. Fiber rich diet (polysaccharides) also has some effect on blood glucose level.

Other Conditions

Hyperactivity: Greater activity, ease of stimulation and other hyperactive signs suggesting an association of sugar intake and hyperactivity.

Dental caries: Dental caries is the only health problem caused by sugar. Better dental care can greatly reduce the incidence of caries.

Sources of Carbohydrates

Starch and sugars constitute the main carbohydrates in human diet. Grains and vegetables constitute the primary source of the starch while fruits may contain considerable amount of sugars. Small amount of glycogen is present in the meat and seafood. The common sources of different carbohydrates are as follows:

Monosaccharides: Corn syrup, fiuits, honey.

Disaccharides: Sugarcane, sugar beets, milk, germinating cereal grains.

Polysaccharides: Cereal grains, legumes, potatoes and other vegetables, liver, muscle tissues, algae and sea weeds.

Many fruits contain large amounts of organic acids like citric and malic acids. Though these acids are not carbohydrates, they contribute to the total intake because of their rapid conversion to carbohydrates in the body.

Classification of Carbohydrates

Carbohydrates or saccharine (Greek: Sacharon, sugar) means "carbon hydrate" which is (CH,O), wherein n>3. Carbohydrates arc classified according to the number of basic sugar or saccharide unit.

Monosaccharides

Monosaccharides are the simplest form of carbohydrate known as simple sugar. Monosaccharides are classified according to their functional group and number of carbon atoms.

Aldoses: If the functional group is aldehyde, as in glucose, it is referred as aldose.

Ketoses: If the functional group is ketose, as in fructose, it is referred as ketoses. Trioses are the smallest monosacchirides of three carbon atoms. Those with four, five, six, seven carbon atoms are tetroses, pentoses, hexoses, and heptoses respectively. Six-carbon aldose is an aldohexose and of ketose is ketohexose.

The three main monosaccharides important in human nutrition are glucose, fructose and galactose.

Glucose: Naturally preformed sweet sugar, glucose is found only in few foods such as corn syrup. Digestion of starch produces glucose. In body, all other types of sugars are converted to glucose. It is also known as "dextrose". (Normal blood sugar level is about 70 - 1 10 mg /lo0 ml.) Glucose is the ultimate energy fuel, which is oxidized in cell to give energy.

Structure of Glucose

Fructose: It is the sweetest simple sugar. Fructose is found in fruits as honey. Fructose is converted into glucose in our body to provide energy.

Structure of Fructose

Galactose: It is not found in free-form in food, but is produced from lactose (milk sugar). Galactose is also changed to glucose for energy, which is a reversible reaction. During milk production, glucose is converted to galactose. Galactosemia, a genetic disorder, is due to the absence/ deficiency of the enzyme required for the conversion of galactose to glucose and thus galactose accumulates.

Structure of Galactose

Oligosaccharides

Oligosaccharides are composed of 2 -10 monosaccharides linked together. Those with two monosaccharides unit are called disaccharides. The three main disaccharides of nhvsiological impoflance are sucrose, lactose and maltose.

Sucrose: Sugarcane beet is a rich source of sucrose. It is a common disaccharide. Sucrose can be found in all molasses, some fruits and vegetables such as pineapple, carrot etc.

Lactose: Lactose is also known as milk sugar. During lactation, it is formed in the body from glucose. It is 116" as sweet as sucrose. Cheese, a milk product, has very little or no lactose.

Structure of Lactose

Maltose: Commercial malt products of starch breakdown and germinating cereal grain's are the rich source of maltose. It is an important metabolic carbohydrate and an intermediate product of starch digestion.

Structure of Maltose

Polysaccharides

Polysaccharides are made up of many saccharides (simple sugar) units. The most important polysaccharide in human nutrition is starch. Other polysaccharides are glycogen and dextrin. The bulk of animal diet is composed of non-digestable forms of dietary fiber e.g., cellulose. Polysaccharides are of two types:

Homopolysaccharides and Heteropolysaccharides.

i) Homopolysaccharides

They yield only one type of monosaccharide (glucose) upon complete hydrolysis. Some important homoploysaccharides are as follows: 

Starch: It is made up of many glucose units attached in a branch chain manner. Actually, it is a mixture of two polymers, amylase (10-20 per cent) and arnylopectin (80-90 per cent). It yields only glucose on digestion. Starch is the most important source of dietary carbohydrate in the world. It is an important part/component of human nutrition Ad health. In many countries, starch is the staple food material forming the bulk of the diet. Cereal grains, legumes, potatoes and many vegetables are rich in starch.

Dextrin: Dextrin is formed as an intermediate product in the break down of starch.

Starch to Glucose 

Glycogen: The storage carbohydrate in animals is glycogen, also known & animal starch. In fact, it is a polymer of glucose similar to amylopectin but with high branching and its branches are smaller. It is formed during cell metabolism and stored in small amounts in liver and muscle tissues. During fasting period such as sleep hours, glycogen provides immediate energy fuel or glucose for muscle action. Dietary carbohydrates are needed to maintain glycogen stores. Low dietary carbohydrate intake causes symptoms like fatigue, dehydration and excessive protein breakdown.

Cellulose: Cellulose is the main component of the framework of plant cell wall. The repeating unit is a disaccharide cellobiose which is made up of two units of D glucose joined by P- l,4 glucosidic linkage, It provides most of the substances labeled "crude fiber". The main food sources are stem and leaves of vegetables, seed and grain coverings, skin and hulls. Humans cannot digest cellulose. Human lack the necessary digestive enzymes which can break P- l,4 glucosidic linkage. Therefore, cellulose remains undigested. Non-cellulose fibers absorb water and have slow gastric emptying time. They are gum like water-soluble substances that aid in binding cholesterol and controlling its absorption. They provide bulk for normal intestinal muscle action to prevent colon pressure.

Structure of Cellulose

ii) Heteropolysaccharides

These are the polysaccharides, which on complete hydrolysis yield more than one particular type of components (sugar acids, amino sugars as noncarbohydrates). These are also referred as non-cellular portion of plant. Some of the important heteropolysaccharides are:

Hemicellulose: The constituents of hemicellulose are xylose, arabinose, uronic acid, glucose and galactose. It is more digestible than cellulose.

Chitin: It forms the structural element in lower plants and in invertebrates. Its subunits are 2-acetarnido-2-deoxy-D-glucopyranose linked by P-1,4, glycosidic bonds.

Pectin: 1t is composed of galactouronic acid chain with arabinose, glucose and xylose. It is used in fruit conserving industry.

Gums: The complete hydrolysis of gums yields arabinose, glucose, rhamnose, glucuronic and galacturonic acids. In nature, it occurs in the form of copper and magnesium salt.

Mucilages: According to source, their constituents differ. Mainly composed of arabinose, galactose, rhamnose and galacturonic acid.

Classification of Carbohydrates