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PLANT BIOCHEMISTRY:TECHNIQUES AND PROCEDURES

G. Nagaraj
  • Country of Origin:

  • Imprint:

    NIPA

  • eISBN:

    9789389547542

  • Binding:

    EBook

  • Number Of Pages:

    506

  • Language:

    English

Individual Price: 3,795.00 INR 3,415.50 INR + Tax

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This book is aimed at helping the analyst with respect to analysis of samples, mainly, plant material. The book is divided into two parts. o The first part deals with the different techniques involved in the biochemical analysis. The theoretical aspects of the same are presented in detail. The mechanism and some information on the buildup of the equipments are furnished. The need and scope of the instruments and their utility are also presented. o The second part deals with specific methods of analysis. Analytical methods of sugars, amino acids, proteins, fats, enzymes and their components are presented. Nucleic acid, vitamin, antinutrient (toxicants) and mineral analytical methods also have been included. o Information on alkaloid and pesticide residue analytical methods etc. has also been furnished. In many cases two or more methods have been given. o They have been given in such a way that they include reagents, apparatus and step wise procedures. o Final calculations needed for arriving at the concentration of the constituents have also been included.

0 Start Pages

Wide diversity exists within and across the species of the plant kingdom. Plants, in general, have extensive utility in our day to-day lives and for the maintenance of congenial environment. The utility of the plants and their products depend on their composition and quality. Useful components like sugars, proteins, fats and other nutrients like minerals and vitamins are present in varying proportions in the plants. Additionally, antinutrients and toxins which are harmful to the humans and animals are present. However, some of the components present are useful as medicine to the living beings, as also, animals. Some chemicals used in growing and increasing the production of crops, apart from having a positive influence, have negative effects on the health and environment. Hence assay of the plants and their products is essential to understand their quality and utility. This book deals with various methods and procedures of analysis of the beneficial and harmful constituents of the plant. Attempts have been made to compile highly useful and more practical procedures in analysis of the components. The book deals with theoretical aspects of the analytical techniques like chromatography, U.V., I.R., N.M.R., Mass and other photometric techniques. Even radiochemical and radio- immunoassay methods find a place. Traditional methods like volumetry, gravimetry, conductometry, polarimetry, etc are also included. Methods of analysis have been grouped into sugars, fats, proteins, enzymes, nucleic acids, antinutrients, toxins, pesticide residues, alkaloids, plant nutrients etc. Wherever available more than one procedure is listed. The analyst can follow any procedure depending on the convenience and facility available in the laboratory. Each method gives information relating to the principle, reagents and equipment needed, actual procedure stepwise and required calculations.

 
1 Introduction

Analysis of materials or samples is essential to understand their nature and quality. In recent years it has become mandatory to display the composition of food as well as non-food items. This is because of the need for their safety from the point of view of their day to day use. Environmental awareness has further imposed many restrictions on items of wide ranging nature. Analytical information gained from a laboratory is highly useful in knowing the qualitative and quantitative composition of the material.

1 - 6 (6 Pages)
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2 Chromatography 

Chromatography is a general technique available for the separation of closely related compounds in a sample. The term chromatography is derived from Greek where chroma means colour and graphein means to write. It is a very useful technique for both qualitative (preparative ) and quantitative (analytical) analyses. The separation is effected by the differential distribution of the components between two immiscible phases, namely, stationary and mobile phases. The various constituents of the mixture travel at different speeds, causing them to separate. The separation is based on differential partitioning (partition coefficient) between the mobile and stationary phases. The stationary phase is a porous medium through which the sample mixture percolates under the influence of a moving solvent (mobile phase).

7 - 10 (4 Pages)
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3 Paper Chromatography

Paper chromatography (P.C.) is the easiest to perform and requires simple and ordinary apparatus. It easily provides qualitative information since components of a mixture can be separated based on their mobilities or molecular weights. It also can provide quantitative information if some special attention and calculation procedures are followed. Paper chromatography is a technique that involves placing a small dot or line of sample solution on to a strip of chromatography paper. The paper is placed in a jar containing a shallow layer of solvent and sealed. As the solvent rises through the paper, it meets the sample mixture, which starts to travel up the paper with the solvent. This paper is made of cellulose, a polar substance, and the compounds within the mixture travel farther if they are non-polar. More polar substances bond with the cellulose paper more quickly, and therefore do not travel as far.

11 - 12 (2 Pages)
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4 Column Chromatography

Column chromatography is a separation technique in which the stationary bed is in a tube. The particles of the solid stationary phase or the support coated with a liquid stationary phase may fill the whole inside volume of the tube (packed column) or be concentrated on or along the inside tube wall leaving an open, unrestricted path for the mobile phase through the tube (open tubular column). Differences in rates of movement through the medium are calculated as different retention times of the sample.   The separation of compounds in the column chromatography takes place based on the phenomenon of adsorption. Here the substance gets attracted by electrostatic forces to the surface of a unit particle. If the substance is in solution and the particle insoluble in the solvent, then part of the substance is adsorbed and part remains in solution. The ratio between the amount adsorbed and the amount in solution is a constant called adsorption coefficient. The separation takes pace based on the differences in the adsorption coefficients.

13 - 16 (4 Pages)
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5 Thin Layer Chromatography

Kirchner was the first in 1950 to think of thin layers. But it was Egon Stahl in 1958 who was responsible for bringing out standard equipment and related procedures to popularize thin layer chromatography (TLC). TLC is a modified form of column chromatography. Hence it is also called open column chromatography. The adsorbent is spread over a supporting material (glass or plastic sheets) to form a thin layer of adsorbent. As a binder, plaster of Paris or gypsum is added to the adsorbent material like silica gel (hence silica gel TLC). The adsorbent is spread over the plate as a thin layer of 0.25 or 0.5 mm. The adsorbent to water ratio is 1:2. It is initially allowed to air dry, followed by drying in an oven at 110oC for 1-2hr or overnight (activation of TLC plates) after which the plate is ready for thin layer chromatography.

17 - 20 (4 Pages)
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6 Electrophoresis

Electrophoresis is the migration of particles under the influence of a direct electric current. There are two requirements for this process to be carried out. First the particles to be separated should be charged or at least should accept charge. Proteins, amino acids, nucleotides etc. conform to this requirement. Second, the medium used for separating the compounds also should carry charge. The mobilities of the ions depend on the nature of the electrolyte solution, the concentration and temperature. The cations and anions move in opposite directions with the cations moving towards the anode and the anions towards the cathode.

21 - 24 (4 Pages)
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7 Ion Exchange Chromatography

This technique is used in the separation of ionised and ionisable compounds.It consists of an insoluble matrix to which charged groups are covalently bound. The charged groups are associated with mobile counter ions. These counter ions can be reversibly exchanged with other ions of the same charge without altering the structure of the matrix. The ion exchanger is complex and polymeric. The polymer carries an electric charge that is exactly neutralized by the charges on the counter ions. These active ions are cations in a cation exchanger and anions in an anion exchanger. A cation exchanger consists of polymeric anions and active cations whereas anion exchanger consists of polymeric cations and active anions. Amberlite IR 120 and Dowex 50 WX are cation exchangers while Amberlite IRA 400 and Dowex 1X are anion exchangers. Ion exchangers should be insoluble in water and hydrophilic to allow the ions to pass through. It should be chemically stable and should be denser than water when swollen.

25 - 26 (2 Pages)
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8 Gel-filtration Chromatography

Gel-filtration chromatography or molecular sieve chromatography is a method based on molecular dimension. The gel consists of beads which are composed of dextran polymer (sephadex, agarose or polyacrylamide gels). The separation depends upon the different abilities of the various sample molecules to enter pores which contain the stationary phase. Very large molecules, which never enter the stationary phase, move through the chromatographic bed fastest. Smaller molecules, which can enter the gel pores, move very slowly through the column, because they spend a proportion of their mobility, time in the stationary phase. Molecules are, therefore eluted in the order of their decreasing molecular size.

27 - 30 (4 Pages)
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9 Solvent Extraction

Solvent extraction is mainly used to remove dissolved substances from solutions or soluble material from solids /powders/ solid mixtures. Solvent extraction is explained using distribution law or partition law. The law states that if to a system of two liquid layers made up of two immiscible liquids/ slightly miscible liquids is added a third substance soluble in both layers , then the substance distributes itself between the two layers so that the ratio of concentration in one solvent to the concentration in the second solvent remains constant at a constant temperature.

31 - 34 (4 Pages)
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10 Dialysis, Ultra Filtration and Lyophilization

Dialysis   The main purpose of dialysis in biological research is the removal of small molecular weight (M.W.) constituents from biological fluids. This is achieved by dialysing the material in a cellulose tubing with a pore size of 40-80 A0 (4-8mm) diameter which allows the passage of compounds with molecular weight less than 10,000. The following is the procedure followed: cut the length of the dialysis tubing depending upon the volume to be processed. Open the sides of the tubing with a flow of distilled water and transfer it to a boiling water bath. Do not allow the tubing to dry as it will distort the pore size. Make a bag by tying a knot at one end of the tubing. Transfer the solution to be dialysed into the bag. Tie another knot at the top of the bag. The bag is then put in a beaker containing the solution against which dialysis is to be carried out. In general, one volume of the desired solution is dialysed against 50-100 volumes of buffer. The total period of dialysis could range from 8-48hr. The efficiency of dialysis could be increased by stirring and changing the dialysate solution at frequent intervals.

35 - 38 (4 Pages)
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11 Centrifugation

When a particle revolves around an axis, a force is developed and acts away from the axis of rotation. This force is called centrifugal force. A particle suspended in a medium takes some time to sediment, which depends upon the size, molecular weight, and viscosity or density of the medium under normal “g” (gravity). To speed up the process of sedimentation, the external field of force is allowed to act on the particle which depends also on the distance of the particle from the axis of rotation in addition to the other factors.

39 - 42 (4 Pages)
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12 Gas Liquid Chromatography

Gas chromatography is one of the most valuable techniques available for organic analysis. It has been applied for the separation, identification and analysis of virtually all volatile compounds. In gas chromatography, the mobile phase is gas. When the stationary phase is liquid , it is called gas liquid chromatography (GLC). If the stationary phase is solid, it is called gas solid chromatography (GSC). The sample is transported through a stationary phase with help of an inert carrier gas, namely the mobile phase. The fractionation of the components in the sample mixture takes place based on the partitioning between the stationary and mobile phases.

43 - 50 (8 Pages)
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13 High Pressure Liquid Chromatography

High pressure (or performance) liquid chromatography (HPLC) is more versatile than GC since it is not limited to volatile compounds. The choice of mobile and stationary phases is wider. HPLC has high resolving power, separations are speedier, quantifications are more precise and it is in general, more reproducible. Liquid chromatography basically involves separation of components due to differences in the equilibrium distribution of sample components between the mobile (liquid) and stationary phases.

51 - 54 (4 Pages)
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14 GC/MS and LC/MS

The mass spectrometry (MS) is not very well suited to the analysis of mixtures of similar substances because of the multiplicity of fragment ions. The gas chromatography (GC), of course,  has no ability to identify compounds on its own. The GC/MS can easily overcome these defects and can identify the components (fractionated by GC). The combined instrument of GC/MS is an unexcelled instrument that can identify the compounds after their  fractionation. The GC-MS is composed of two major building blocks: the gas chromatograph and the mass spectrometer. The gas chromatograph utilizes a capillary column which depends on the column’s dimensions as well as the stationary phase properties. The difference in the chemical properties between different molecules in a mixture and their relative affinity for the stationary phase of the column will promote separation of the molecules as the sample travels the length of the column. The molecules are retained by the column and then elute (come off) from the column at different times and this allows the mass spectrometer downstream to capture, ionize, accelerate, deflect, and detect the ionized molecules separately.

55 - 60 (6 Pages)
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15 Spectrophotometry

Spectrophotometry measures how much a chemical substance absorbs light by measuring the intensity of light as a beam of light passes through the sample solution. Chemical compounds normally absorb or transmit light over a certain range of wavelength. Hence spectrophotometry is used to measure the amount of a known chemical substance. It is one of the most useful methods of quantitative analysis in the laboratory and is widely used. A  colorimeter or spectrophotometer is an instrument that measures the amount of photons (the intensity of light) absorbed after it passes through the sample solution. With the spectrophotometer, the amount of a known chemical substance (concentrations) can also be determined by measuring the intensity of light detected. Depending on the range of wavelength of light source, it can be classified into two different types, namely,1) UV-visible spectrophotometer which uses light over the ultraviolet range (185-400nm) and visible range (400-700nm) of electromagnetic radiation spectrum and 2) IR spectrophotometer which  uses light over the infrared range (700-15000nm) of electromagnetic radiation spectrum.

61 - 66 (6 Pages)
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16 Infrared Spectroscopy

Infrared light (800-1500nm) interacts with molecules at the level of atomic vibrations. An infrared spectrum gives valuable information about the molecular structure. It is rarely used for quantitative purposes and hence concentration measurements are not possible. Infrared light detects vibrations characteristic of functional groups. For example the C=O (carbonyl) group absorbs at 1700 cm-1 (wave number). The main region of interest for analytical purposes is from 2.5- 25µm or 4000- 400 cm-1. At wavelengths below 25µm the radiation has sufficient energy to cause changes in the vibrational energy levels of the molecule, and these are accompanied by changes in the rotational energy levels. The pure rotational spectra of molecules occur in the far infra red region (50-1000 µm) and are used for determining molecular properties.

67 - 70 (4 Pages)
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17 Flame Photometry

When an element burns in a flame it emits radiation characteristic of its identity. Flame photometry is the determination of an element in solution by measurement of emission of light by atoms of the element in flame. Initial tests for identification of a few elements by flame tests are well known. Na burns with yellow flame, K with lilac flame, Ca, with red flame, Cu, with green flame etc. Emission of characteristic radiation by an element and correlation of emission intensity with the concentration of that element form the basis for flame photometry. The sample to be analyzed is prepared in solution and sprayed under controlled conditions into a flame. The light from the flame enters a monochromator to isolate the desired region of the spectrum. A photocell and an amplifier measure the intensity of the isolated radiation. After proper calibration of the photometer with solutions of known composition and concentration, it is possible to correlate the intensity of a given spectral line with the unknown concentration of that element. A calibration curve prepared using known concentrations is useful. Internal standards and addition of known concentration of sample to be quantified are more useful.

71 - 74 (4 Pages)
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18 Atomic-absorption Spectroscopy

Atomic-absorption (AA) spectroscopy uses the absorption of light to measure the concentration of gas-phase atoms. Since samples are usually liquids or solids, the analyte atoms or ions must be vaporized in a flame or graphite furnace. The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels. The analyte concentration is determined from the amount of absorption. Applying the Beer-Lambert law directly in AA spectroscopy is difficult due to variations in the atomization efficiency from the sample matrix, and non-uniformity of concentration and path length of analyte atoms (in graphite furnace of AA). Concentration measurements are usually determined from a working curve after calibrating the instrument with standards of known concentration.

75 - 76 (2 Pages)
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 Atomic-absorption Spectroscopy

Atomic-absorption (AA) spectroscopy uses the absorption of light to measure the concentration of gas-phase atoms. Since samples are usually liquids or solids, the analyte atoms or ions must be vaporized in a flame or graphite furnace. The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels. The analyte concentration is determined from the amount of absorption. Applying the Beer-Lambert law directly in AA spectroscopy is difficult due to variations in the atomization efficiency from the sample matrix, and non-uniformity of concentration and path length of analyte atoms (in graphite furnace of AA). Concentration measurements are usually determined from a working curve after calibrating the instrument with standards of known concentration.

75 - 76 (2 Pages)
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19 Inductively Coupled Plasma Atomic Emission Spectroscopy

Inductively coupled plasma atomic emission spectroscopy (ICP-AES) uses an inductively coupled plasma to produce excited atoms and ions that emit electromagnetic radiation at wavelengths characteristic of a particular element. A plasma is a neutral gas containing a good number of positive and negative ions or free electrons. A plasma can only be created. A combustion flame is one example of a plasma. Advantages of ICP-AES are excellent limit of detection and linear dynamic range, multi-element capability, low chemical interference and a stable and reproducible signal. Disadvantages are spectral interferences (many emission lines), high cost and operating expense and the fact that samples typically must be in solution.

77 - 80 (4 Pages)
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20 NMR Spectroscopy

Nuclear Magnetic Resonance spectroscopy is a powerful and theoretically complex analytical tool. The nuclei of certain isotopes are continuously spinning with an angular momentum, which can give rise to an associated magnetic field.

81 - 84 (4 Pages)
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21 Radiochemical Methods

In 1896, French physicist Becquerel observed that uranium compounds affected a photographic plate that was wrapped inside a black paper. He found that all uranium compounds gave off penetrating rays. He called the production of radiation by uranium compounds “radioactivity”. Madame and Pierre Curie later identified thorium, polonium, and radium as the other radioactive elements.

85 - 92 (8 Pages)
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22 Mass Spectrometry

Mass spectrometry (MS) is a  useful  technique which produces spectra of the masses of the atoms or molecules in a sample.  The spectra are used to determine the elemental or isotopic   details  of a sample. The masses of particles and of molecules, are used to elucidate the chemical structures of molecules, such as peptides and other chemical compounds. Mass spectrometry works by ionizing chemical compounds to generate charged molecules and measuring their mass-to-charge ratios. A sample, which may be solid, liquid, or gas, is ionized, by bombarding with electrons. This may cause some of the sample’s molecules to break into charged fragments. These ions are then separated according to their mass-to-charge ratio, typically by accelerating them and subjecting them to an electric or magnetic field. Ions of the same mass-to-charge ratio will undergo the same amount of deflection. The ions are detected by a mechanism capable of detecting charged particles, such as an electron multiplier. Results are displayed as spectra of the relative abundance of detected ions as a function of the mass-to-charge ratio. The atoms or molecules in the sample can be identified by correlating known masses to the identified masses or through a characteristic fragmentation pattern.

93 - 98 (6 Pages)
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23 Polarimetry

Compounds having one or more asymmetric carbon atoms can rotate the plane of polarized light. Such compounds are called optically active. Measurement   of this property is called polarimetry.   The magnitude and direction in which the plane of polarized light is rotated depend on 1.The nature  of the compound, 2. The  concentration of the solution, 3. The path length of light, 4. The solvent, 5. The wave length of light and  6. The temperature. These variables are related and can be presented in the formula

99 - 102 (4 Pages)
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24 Conductimetry

When a fixed voltage is applied to two electrodes dipping into a solution,a current will flow, depending on the conductivity of the solution. Conductivity measurements do not give information about the nature of the ions in solution. However, they are useful in the quantitative measurement of the ions.

103 - 104 (2 Pages)
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25 Potentiometry

When a metal M is immersed in a solution containing its own ion Mn+, then  an electrode potential  develops. The value of  the  electrode potential  is given by the Nernst equation.

105 - 108 (4 Pages)
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26 ELISA and Radioimmunoassay (RIA)

Immunoassays rely on the ability of an antibody to recognize and bind a specific macromolecule in what might be a complex mixture of macromolecules. In immunology the particular macromolecule bound by an antibody is referred to as an antigen and the area on an antigen to which the antibody binds is called an epitope. In some cases an immunoassay may use an antigen to detect for the presence of antibodies, which recognize that antigen, in a solution. In other words, in some immunoassays, the analyte may be an antibody rather than an antigen.

109 - 112 (4 Pages)
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27 Gravimetric Analysis

Gravimetric analysis describes a set of methods in analytical chemistry for the quantitative determination of an analyte based on the mass of a solid. A simple example is the measurement of solids suspended in a water sample. A known volume of water is filtered, and the collected solids are weighed.   In gravimetry, the analyte needs to be first converted to a solid by precipitation with an appropriate reagent. The precipitate can then be collected by filtration, washed, dried to remove traces of moisture from the solution, and weighed. The amount of analyte in the original sample can then be calculated from the mass of the precipitate and its chemical composition. In some cases, it is easier to remove the analyte by evaporation. The analyte might be collected—perhaps in a cryogenic trap or on some adsorbent material such as activated carbon—and measured directly. Or, the sample can be weighed before and after it is dried; the difference between the two masses gives the mass of analyte lost. This is especially useful in determining the water content of complex materials such as foodstuffs.

113 - 116 (4 Pages)
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28 Volumetric Analysis

Titration, also known as titrimetry, is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte.  Since volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the titrant or titrator is prepared as a standard solution. A known concentration and volume of titrant reacts with a solution of analyte or titrand  to determine concentration. The volume of titrant reacted is called titre. Volumetric analysis originated in late 18th-century in France.

117 - 124 (8 Pages)
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29 Amplification and Sequencing of Nucleic Acids

DNA and RNA are the carriers of genetic information in all the living organisms. The study and analysis of the genetic code can provide information that can be used in clinical diagnostics, drug discovery, genetic engineering and forensic sciences. Hence there is need to understand the techniques in isolation of DNA and RNA followed by their amplification and sequencing.

125 - 128 (4 Pages)
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30 Methods of Analyses

Organic material especially, seeds, grains, leaves, fruits and nuts contain prominently three groups of compounds. They are carbohydrates, proteins and fats/oils, mostly in that order. They also contain 3-5% minerals and smaller quantities of vitamins and other minor constituents. Cereal grains contain more of carbohydrates while oilseeds and nuts contain more oil. Tree nuts and even oilseeds may contain 30-50% protein while cereal grains contain 5-8% protein only. The starch and sugar contents of oilseeds may be less than 10% while the oil content of cereal grains ranges around 5%. The actual content and the composition of these groups of compounds really account for their quality as well as commercial value.

129 - 130 (2 Pages)
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31 Carbohydrates and their Methods of Analysis

Carbohydrates are the most abundant biomolecules on earth. They occur in nature as glucose, starch and cellulose etc. Each year, photosynthesis converts more than 100 billion metric tonnes of carbon dioxide and water into starch, cellulose and other plant products. Carbohydrates are polyhydroxy aldehydes or ketones and their derivatives. They provide 4K calories of energy per gram. They promote utilization of lipids and reduce wastage of proteins. They are readily available in roots, tubers, cereal grains, sugarcane and sugar beet.

131 - 166 (36 Pages)
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32 Fats / Oils / Lipophilic Constituents

Lipids are a diverse group of chemical molecules. They are generally insoluble in water but soluble in organic solvents. Lipids include long-chain hydrocarbons, alcohols, aldehydes, fatty acids, and their derivatives, especially, glycerides, phospholipids, glycolipids and sulfolipids. Other compounds like sterols, fatty acid esters of sterols, vitamins A, D, E, and K, carotenoids, and other poly-isoprenoids also are part of the lipids. Oils and fats are mainly triglycerides and neutral molecules. Those in the liquid state at ambient temperatures are called oils while those in the solid state are called fats. Lipids and lipid components have varied uses in the food and non food sectors. Vegetable and animal matter contain a variety of these constituents in different proportions. It is neccessry to evaluate the composition and quality of these constituents from the point of view of their utility.

167 - 222 (56 Pages)
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33 Amino Acids and Proteins

The word protein was first coined in 1838 to emphasize the importance of this class of molecules. The word is derived from the Greek word proteios which means “of the first - rank”. Proteins are polymers/macro molecules made up of several amino acids. When there are more than 50 amino acids in a chain, the polypeptide is normally called a protein. Each protein in the cells of living beings has a unique sequence of amino acids that determines its biological function. The proteins are folded into specific defined structures, which are maintained by large number of relatively weak bonds. The three dimensional structure is well defined and suited to it’s specific function.

223 - 262 (40 Pages)
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34 Enzymes

Enzymes are organic catalysts produced by living organisms. They make possible biochemical reactions. Hence they are called biocatalysts. They are mostly a specialized class of proteins. However, there are some non-protein enzymes like ribozymes, which are RNAses. Enzymes speed up reactions at ambient temperatures. This is in contrast to chemical reactions like saponification of lipids which take place when lipids are boiled for a few hours with concentrated alkali. Enzymes, namely, lipases, hydrolyze lipids at body temperatures in minutes. They are superior to chemical catalysts by a factor of 107 to 1014 . An enzyme may be a simple protein or a complex protein. They are produced by cells and are mostly globular proteins. Each cell contains an estimated 3000 different enzymes.

263 - 298 (36 Pages)
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35 Nucleic Acids

Nucleic acids were first discovered in 1868 by Friedrich Meischer. Nucleic acids are high molecular weight polymers that are present in our cells. They store and transfer genetic material from generation to generation. Knowledge of how genes are expressed and how they can be manipulated is becoming increasingly important for understanding of nearly every aspect of biochemistry. These macromolecules p ass on information for cellular growth and reproduction. All the genetic information in the cells is called the genome. Every time a cell divides, the information is copied and passed on to the new cells.

299 - 306 (8 Pages)
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36 Vitamins

Vitamins are essential organic nutrients required by an organism in small quantities. They are essential since they cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. The term vitamin does not include other essential nutrients like dietary minerals, essential fatty acids, or essential amino acids which are needed in larger quantities than vitamins. The term vitamin is derived from “vitamine,” coined in 1912 by the Polish biochemist Funk. The name is from vital and amine, meaning amine of life. Thirteen vitamins are generally recognized presently. Vitamins are used in small quantities by an organism to keep it in a healthy condition.

307 - 328 (22 Pages)
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37 Phenolics and Antinutrients

Phenol is normally a benzene ring containing an –OH group, and hence an aromatic alcohol. The term “phenolic” refers to similar aromatic compounds with one or more -OH groups. Phenolics constitute one of the most widespread classes of secondary metabolites. Commonly talked about class of compounds like anthocyanins, flavonoids, lignins, tannins, coumarins and chalcones are all phenolic substances. Phenolics are water insoluble substances. However, the water solubility increases with the increase in the number of -OH groups. Phenolics absorb electromagnetic radiation strongly. Many of the phenolics absorb in the visible part of the spectrum (Ex. anthocyanins) and are coloured. Phenolics are produced in plants by 1. Shikimate pathway through phenylalanine (C6-C3) and 2. Acetate/malonate pathway.

329 - 366 (38 Pages)
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38 Toxins

Certain constituents associated with plants are toxic. When such items are consumed by men and animals, they become hazardous. Mold growth on food items may be the cause of toxicity. Some of them are called mycotoxins. Aflatoxins are the best examples of such a group of compounds. Sometimes processing also produces some toxins. Fumigants, smoke and some metals (mercury, lead, cadmium, arsenic etc.) used for such purposes are some such toxic constituents. Pesticides used in protecting the crops and grains during storage remain on the items and the residues are hazardous.

367 - 390 (24 Pages)
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39 Alkaloids

Alkaloids are of plant origin and are alkaline in reaction. They contain N as part of a hetercyclic ring. They exhibit pharmacological activity. Presently more than 2000 alkaloids are known. They have a lot of uses in medicine and as  flavoring agents, psychoactive agents, pain killers and as pesticides.

391 - 396 (6 Pages)
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40 Plant Nutrients

Sixteen chemical elements are known to be important to a plant’s growth and survival. The sixteen chemical elements are divided into two main groups: non-mineral and mineral.  The Non-Mineral Nutrients are hydrogen (H), oxygen (O), and carbon (C). These nutrients are found in the air and water.    In a process called photosynthesis, plants use energy from the sun to change carbon dioxide (CO2 - carbon and oxygen) and water (H2O- hydrogen and oxygen) into starches and sugars. These starches and sugars are the plant’s food. Since plants get carbon, hydrogen, and oxygen from the air and water, there is little the farmers and gardeners can do to control  how much of these nutrients a plant can use.

397 - 442 (46 Pages)
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41 Plant Pigments

Plant pigments impart colour to the different components like leaves, flowers, fruits etc. They in turn are responsible for the colour of raw food, we eat. Pigments like chlorophyll, anthocyanins, flavonoids, tannins, xanthones etc. are the different pigments that are present in plants. The primary function of pigments in plants is photosynthesis, which uses the green pigment chlorophyll along with several red and yellow pigments that help to capture as much light energy as possible. Chlorophyll is green in colour. Carotenoids like a, b, and g, carotenoids are yellow in colour. Lycopene is red in colour. Flavones and falvonols are also yellow in colour. Anthocyanins are purple and magenta in colour. Other functions of pigments in plants include attracting insects to flowers to encourage pollination. The assay of pigments is mostly based on their native colour.

443 - 454 (12 Pages)
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42 Pesticide Residue Analysis

Chemicals in the form of insecticides ,fungicides and herbicides are extensively used in large numbers in agricultural production. Commercial production of some crops would be impossible if chemicals are not used. Small quantities of chemical residues often remain in such crops and the harvested grains and other products. The residues of pesticides  have been observed in small quantities (ppm level) in soil, water, agricultural produce  and even in animal tissues and their products like meat and  milk. They finally reach the consumer, namely, man (and even animals). Even the environment  is  now-a-days polluted with pesticides and other chemicals harmful to the humans. In view of the importance and seriousness of the problem the residues need to be estimated in the food and non-food products to assess their safety. Analytical details of a few pesticide residue procedures are presented below. Specialized texts may be consulted for  more extensive information.

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43 End Pages

Appendix Important chemical terms Percentage It is expressed as either weight by volume or as volume by volume.  It is the amount of solute in grams or ml in 100 ml of solvent.  For ex. 5g solute in 95g solvent is 5% w/w solution. A 30 ml solute in 70ml solvent is 30% v/v solution. A 20g solute dissolved and made up to 100ml solvent is w/v solution.   Molarity or molar solution (M) It is the number of moles ( gram molecular weight) of solute dissolved in a litre of solution.  For ex. if one gram molecular weight of a salt is dissolved in one litre of water, it is called 1M solution.

 
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