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Climate, soil, input and management factors influence the crop yield. Weather is the most important natural input that affects the agricultural production and productivity. The agricultural activities starting from the land preparation to harvest and post-harvest storage are greatly influenced by the weather. The effects of weather on crops may be direct such as those of precipitation, solar radiation, humidity, temperature, etc., or indirect such as those of pest, diseases, weed competition, etc. Thus, the success or failure of a crop is determined by the prevailing weather conditions. Although influence of weather conditions on yield is well established, the quantitative assessment is not always straight forward and simple. The quantitative assessment of the effect of weather on crops is an important application of agrometeorology. The relationship between weather and crop production has been understood through crop weather modelling and study on this aspect through a systematic approach started a century ago. The aim of developing crop weather models is to ensure better utilisation of resources and hence a more environmental friendly and sustainable agriculture.

A model is a schematic representation of the conception of a system or an act of mimicry or a set of equations, which represents the behaviour of a system. Its purpose is usually to aid in explaining, understanding or improving performance of a system. Agricultural models are mathematical equations that represent the reactions occurring within the plant and the interactions between the plant and its environment. However, it is a difficult task to represent any system completely in mathematical terms because of the complexity of the system. Universal models do not exist for the agricultural systems and agricultural models are built for specific purposes and the level of complexity is accordingly adopted. Different models are developed for different subsystems and several models may be built to simulate a particular crop or a particular aspect of the production system. Crop weather models may be defined as a simplified representation of the complex relationships between weather or climate on one hand and crop performance such as growth, yield or yield components, on the other hand by using mathematical and/or statistical techniques

The word ‘remote sensing’ was coined by Evelyn L. Pruitt, an American Geographer in 1960. Remote sensing is defined as collection and interpretation of information about a target without being in physical contact with it. Remote sensing is the science and art of obtaining information about an object, area or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area or phenomenon under investigation (Lillesand and Keifer, 1994).

The information needs a physical carrier to travel from the objects/events to the sensors through an intervening medium. Any force field such as gravity, magnetic or electromagnetic could be used for remote sensing. However, the electromagnetic radiation is conventionally used as an information carrier in remote sensing. Remotely sensed data may be gathered by different devices, including sensors, film cameras, digital cameras and video recorders. Instruments capable of measuring electromagnetic radiation are called sensors.

Remote sensing is nothing but opposite of astronomy. In astronomy, man looks from the earth to the sky to understand and gain more knowledge about the celestial objects. But remote sensing refers to going upward in the sky to look downwards to understand and gain more knowledge about terrestrial objects. In remote sensing, the aerial sensor technologies are used to detect and classify objects on earth by means of electromagnetic radiation.

Weather forecasting is the application of science and technology to predict the state of the atmosphere for a given location. Weather forecasts are made by collecting quantitative data about the past and current state of the atmosphere on a given place and using scientific understanding of atmospheric processes to project how the atmosphere will evolve on that place. Weather warnings are important forecasts because they are used to protect life and property. Forecasts based on temperature and precipitation is important to agriculture.

Agricultural production is highly dependent on weather, climate and water availability, and is adversely affected by weather and climate related disasters. In many developing countries where rainfed agriculture is the norm, a good rainy season means good crop production, enhanced food security and a healthy economy. Failure of rains and occurrence of natural disasters such as floods and droughts can lead to crop failures, food insecurity, famine, loss of property and life, mass migration, and negative national economic growth (Sivakumar, 2006).

Farming in many parts of the world, especially in the arid and semiarid regions is risky, because climate is highly variable. In some developing countries as much as 80% of the variability in agricultural production is due to the variability in weather conditions. This production variability in agriculture has immediate and important macroeconomic impacts. A timely seasonal forecast of favourable conditions could permit farmers to adjust cropping patterns and input use in order to benefit fully from these conditions. Also, a timely forecast could give the marketing system and downstream users, such as the food processing industry, time to prepare for a bountiful harvest (Arndt et al., 2000). It is important to remember that under rainfed conditions, even a less reliable, but earlier forecast may be more valuable than an accurate but late forecast (Mjelde et al., 1998).

Many aspects of the global climate are changing rapidly. Evidence for changes in the climate system abounds, from the top of the atmosphere to the depths of the oceans. The climate system is the highly complex system consisting of five major components; the atmosphere, the hydrosphere, the cryosphere, the land surface and the biosphere, and the interactions among them. The climate system evolves in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations and human-induced forcings such as the changing composition of the atmosphere and land-use.

The term ‘climate variability’ is often used to denote deviations of climatic statistics over a given period of time (e.g., a month, season or year) from the long-term statistics relating to the corresponding calendar period. In this sense, climate variability is measured by those deviations, which are usually termed anomalies.

‘Climate change’ refers to a statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period (typically decades or longer). Climate change may be due to natural internal processes or external forcings, or due to persistent anthropogenic changes in the composition of the atmosphere or in land use. The United Nation’s Framework Convention on Climate Change (UNFCCC) defines ‘climate change’ as ‘a change of climate behaviour which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods’. The UNFCCC thus makes a distinction between ‘climate change’ attributable to human activities altering the atmospheric composition, and ‘climate variability’ attributable to natural causes. Climate change is a long-term shift in weather conditions measured by changes in temperature, precipitation, wind, snow cover, and other indicators. It can involve both changes in average conditions and changes in variability, including, for example, changes in extreme conditions.

A key difference between climate variability and change is in persistence of ‘anomalous’ conditions. In other words, events that are used to be rare occur more frequently, or vice versa. Occasionally, an event or sequence of events occurs that has never been recorded before, such as the exceptional tsunami in the Indian Ocean in 2004 or hurricane season in the Atlantic in 2005. Yet even that could be a part of natural climate variability. If such a season does not recur within the next 30 years, by looking back it could be called as an exceptional year, but not a ‘climate change’. Only a persistent series of unusual events taken in the context of regional climate parameters can suggest that a potential change in climate has occurred.

Weather and climate have great influence on farm animal production. The environment in which an animal lives is referred to as its habitat. A habitat includes both biotic (living) and abiotic (nonliving) components of the animals’ environment. Abiotic components of an animal’s environment include temperature, humidity, oxygen, wind, soil composition, day length and elevation. Knowledge of how potential environmental stressors (ambient temperature, humidity, thermal radiation, air speed, etc.) can directly and adversely affect animal performance, health and wellbeing is also required for a successful animal farming. The indirect consequences of weather include their impact on feed quality and availability.

Birds and mammals are warmblooded (endotherms or homeotherms), possessing a thermoregulatory system that maintains a stable body temperature and uniform internal environment (homeostasis) by converting food energy into heat. All metabolic processes generate substantial heat and much of this is retained within the body of homeotherms by insulating layers of fat, feathers or fur. Dairy cattle, like other warmblooded animals, function most efficiently in environments where they can maintain their body temperature at around 38° C. Tissue and cellular metabolism and the underlying biochemical reactions that sustain life and productive functions need body temperature to be maintained within very narrow limits. Relatively small increases in body temperature result in the breakdown of body protein and a significant depression in production.

Climate change, particularly global warming has complex impacts on domestic animal production system affecting feed supply, challenging thermoregulatory mechanism resulting thermal stress, emerging new diseases due to change in epidemiology of diseases and causing many other indirect impacts. So, climate change will have farreaching consequences for dairy and meat production, especially in vulnerable parts of the world where it is vital for nutrition and livelihoods. Due to poor availability of good quality feed and fodders in India, animals are generally maintained on poor quality grasses available in the pastures or are stallfed, mainly on crop residues. India is already deficit in feed and fodder. These shortages would be further aggravated by the adverse effects of global warming on fodder crop production.

Many diseases, nematodes, insects and weeds affect crop production, causing severe yield loss. Weather is the most important factor that determines the geographical distribution of these crop pests. The local weather patterns have a significant impact on the abundance of diseases and insect pests in the crops. The severity of disease and pest development depends on the combination of weather conditions during the growing season and is variable from season to season. The weather conditions include temperature (both the maximum and the minimum), light, rain, humidity, dew, cloudiness, sunshine, wind, air currents, evaporation, snow and atmospheric pressure. However, among these weather parameters, temperature and humidity play the major roles in infection of crops due to insect pests and diseases.

Different crops are grown over a wide range of agroecosystems. Though the crops are raised in varied climates, ranging from very hot to very cold, and very wet to very dry, across temperate, tropical and semiarid zones, they are very sensitive to climate. The crop production is dependent on climatic parameters like rainfall, light, temperature, relative humidity and carbon dioxide concentration. Each kind of cultivated crop plants has its own optimum growth requirements. Breeding and selection of new cultivars have allowed for a greater adaptability to less favourable growing conditions than was possible in the past, but the inherent climatic requirements of a specific kind of crop have not changed materially. Crop management is therefore very much about managing climate risk so as to have financially viable and sustainable agricultural systems. Professor Henry Nix of the Australian National University posed three questions that need to be addressed when considering what crop can be grown where (Nix, 1981).

Climate classification systems are ways of classifying the world’s climates. One purpose of climatic classification is to group together places with similar climatic characteristics. That means if an area or region is categorised under a particular climatic type, it possesses broadly uniform characteristics with respect to climate. Classifications have been based on climatic elements such as temperature and precipitation, which are measurable, and on differences in tree species, soil characteristics, topography, etc. The varied nature of earth’s surface and the many interactions that occur among atmospheric processes give every location on the earth a distinctive climate.

Although the delineation of distinct climates may seem likely a very straightforward job, establishing the criteria by which climates are delineated requires considerable subjectivity. There are many ways of classifying the climate depending on the user and the level of understanding of the climate system at a given time. Different regions of the same climate type constitute isoclimatic regions. Identification of isoclimates helps in the transfer of agro-technology and suggesting new cropping pattern. Climatic classification is based on two approaches, viz., generic or empirical approach and genetic approach. In the generic approach the classification is based on the observed climatic elements or their effects on the phenomena, usually vegetation or humankind. The genetic classification is based on climatic controls such as general circulation, net radiation and moisture fluxes.

The concept of climate classification was originally brought out to delineate natural vegetation, which is dependent on rainfall and temperature. Climate classification is unique tool to find out different climate types across the globe, out of which isoclimates or homoclimates can be traced out.

The climate of a particular place is the function of a number of factors such as latitude and its influence on solar radiation received, air mass influences, location of global high and low pressure zones, heat exchange from ocean currents, distribution of mountain barriers, pattern of prevailing winds, distribution of land and sea, and altitude.

Meteorological hazards are severe and extreme weather and climate events that occur in all parts of the world, although some regions are more vulnerable to certain hazards than others. Meteorological hazards include cyclones, droughts, floods, hurricanes, hailstorms, heat waves and tornadoes. The hazard is distinguished from an extreme event and a disaster. An extreme event is simply an unusual event; it does not necessarily cause harm. A disaster is an event that does cause harm in significant amounts. Meteorological hazards are often called as natural hazards. The natural hazards become natural disasters when people’s lives and livelihoods are destroyed.

Hydrological hazards are the result of either excess or a severe lack of water, i.e., flood or drought. Hydrometeorological hazard is a process or phenomenon of atmospheric, hydrological or oceanographic nature that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage. Human and material losses caused by natural disasters are a major obstacle to sustainable development. By issuing accurate forecasts and warnings in a form that is readily understood and by educating people about how to prepare against such hazards, before they become disasters, lives and property can be protected.

Evapotranspiration is the combination of two separate processes named evaporation and transpiration. Evaporation accounts for the movement of water to the air from sources such as the waterbodies and soil. Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapour through stomata in its leaves. So evapotranspiration is a bio-physical process.

Evaporation

The change of state of water from liquid to the vapour and its diffusion into the atmosphere is referred to as evaporation. During evaporation, water molecules absorb energy which gives them the motion required to escape from the surface of liquid and become a gas. Since a certain amount of energy is consumed in the process of evaporation, the remaining liquid is cooled by an equivalent amount. Thus, the process of evaporation is always accompanied by a cooling effect.

As evaporation proceeds, the surrounding air becomes gradually saturated with water vapour and the process will slow down and might stop if the wet air is not transferred to the atmosphere. The replacement of the saturated air with drier air depends greatly on wind speed. Hence, solar radiation, air temperature, air humidity and wind speed are meteorological parameters to be considered when assessing the evaporation process.

In agrometeorology, evaporation is defined as the maximum possible loss of moisture from a wet, horizontal, flat surface exposed to weather parameters, which exist in the vicinity of plants. Evaporation is an essential part of the water cycle. It is the primary pathway through which water moves from the liquid state back into the water cycle as atmospheric water vapour. The oceans, seas, lakes and rivers provide nearly 90 per cent of the moisture in the atmosphere via evaporation, with the remaining 10 per cent being contributed by plant transpiration. A very small amount of water vapour enters the atmosphere through sublimation, the process by which water changes from a solid (ice or snow) state to a gaseous one, bypassing the liquid phase.

The word ‘monsoon’ is derived from the Arabic word mawsim meaning season. The Arabs during their travel towards India recognised that by June strong southwesterly winds commence over the Arabian Sea and bring a lot of rains to the subcontinent. The term was first used in English in British India and neighbouring countries to refer to the big seasonal winds blowing from the Bay of Bengal and Arabian Sea in the southwest bringing heavy rainfall to the area. In the Indian subcontinent, monsoon is one of the oldest weather observations, an economically important weather pattern over June through September every year, and the most anticipated weather event and unique weather phenomenon. Due to its effects on agriculture, flora and fauna, and other economic, social, and environmental effects, a monsoon is one of the most anticipated, followed and studied weather phenomena of the Indian subcontinent. It has significant impact on the overall well-being of subcontinent residents.

The term ‘monsoon’ is customarily used in India to refer to the rainy season during the northern hemisphere summer from June to September and is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea. Now the term monsoon has been broadened to include almost all of the phenomena associated with the annual weather cycle within the tropical and subtropical land regions of the earth.

Precipitation is water in liquid or solid forms, falling on to the earth. In other words, precipitation is the deposition of atmospheric moisture on earth. Formation of clouds does not mean precipitation. Precipitation involves condensation, growth of hygroscopic nuclei, cooling of nuclei at different stages and their fall on to the earth’s surface. There may be several clouds but no precipitation. If the cloud particles are too small and remain suspended in the sky, they may not fall on the earth. Under certain conditions, water particles formed tend to fall but do not reach the surface since they get evaporated on the way. Only when the cloud droplets or ice crystals grow to certain size and can no more remain floating due to buoyancy of air, do they fall as precipitation.

Precipitation is the major source of water to all the living organisms on the earth. All the water sources on the earth depend on precipitation only.

Forms of precipitation

Precipitation form is the state that the moisture is in, i.e., liquid, freezing, or frozen (solid). Different forms of precipitation may occur together, such as mixed rain and snow; but such an occurrence is simply a mixture of forms, not a separate form of precipitation. Because atmospheric conditions vary greatly both geographically and seasonally, several different forms of precipitation are possible. All forms of precipitation are collectively termed hydrometeors. Hydrometeors have been classified into 50 specific types. Out of these precipitation forms, only rain (liquid form) and snow (solid form) make significant contribution to total precipitation. In many parts of the world, the term rainfall is used interchangeably with precipitation.

Clouds are visible mass of little drops of water or frozen crystals suspended in the atmosphere above the surface of the earth. The World Meteorological Organisation defined cloud as a visible aggregate of minute particles of water or ice or both, in the free air. This aggregate may include larger particles of water or ice and particles such as those present in fumes, smoke or dust.

Clouds are the most important form of suspended water droplets caused by condensation. The typical size of these water droplets and ice crystals range from less than 1 μm to 50 μm. When surrounded by billions of other droplets or crystals, they become visible as clouds. In the atmosphere sufficient moisture is required to allow condensation to take place. Then, moisture needs a suitable surface upon which it can condense. In free air, condensation begins on hygroscopic nuclei such as aerosols. These are microscopic particles and include dust, smoke, salts and chemical compounds. Nuclei range in size from 0.001 μm radius to over 10 μm. On an average, oceanic air contains one million condensation nuclei per litre and land air holds some 5 or 6 millions. On hygroscopic particles such as sea salts, condensation can begin before the air is saturated. Supersaturation in clouds rarely exceeds one per cent. On an average, clouds contain only four per cent of the total water in the atmosphere at any one time. Almost all clouds exist in the troposphere, although the tops of some severe thunderstorms occasionally extend to the stratosphere. Clouds move along with the wind and remain stationary in calm winds. They grow vertically and horizontally, depending on the temperature of the cloud and its ambient temperature. They may dissipate or precipitate. Under favourable atmospheric conditions, they burst and fall as rain.

Water vapour changes to the liquid water through condensation process. Condensation is the direct cause of the various forms of precipitation. It occurs as a result of changes in air volume, temperature, pressure or humidity. Water vapour can also be converted directly into the solid form through a process called sublimation. The latent heat expended in evaporation is liberated in the process of condensation. Four mechanisms may lead to condensation.

Water is the only substance that exists in the atmosphere in all the three phases, i.e., solid, liquid and gas. The moisture on the earth’s surface is in a constant phase change. The moisture content of the atmosphere is about 0.035% of all fresh water. The atmosphere receives its supply of moisture from the earth’s surface through evaporation from oceans, lakes, rivers, damp soil, etc. and through transpiration from vegetation. Water vapour is the gaseous state of water and is invisible.

The amount of water vapour present in the atmosphere is called atmospheric moisture or humidity. It is a measure of the amount of water vapour dissolved in the air, not including any liquid water or ice falling through the air. While humidity itself is a climate variable, it also interacts strongly with other climate variables. The humidity is affected by winds and by rainfall. Moisture content is determined by the local rate of evaporation, air temperature and the horizontal transport of moisture. Humidity indicates the likelihood of precipitation, dew or fog. It also plays a major role in the heat budget and the weather phenomenon of the atmosphere.

A big layer of air called the atmosphere surrounds the earth. The air within this layer moves from place to place when it warms up or cools down. This moving air is known as wind. In other words, air in motion is called wind. Winds move moisture and heat around the world and also produce much of our weather.

The strength of the wind can vary enormously. Sometimes air moves slowly and the wind is barely noticeable. When the weather is clear there may be a gentle breeze. When the wind is still very light, but it can be felt and there may be rustlings by leaves. At other times, the air can move very quickly and become a gale or hurricane, blowing down trees and damaging electric poles and buildings.

Winds are part of a global air circulation system that acts to balance temperature and pressure around the world. Different parts of the world receive different amounts of heat from the sun. This differential heating in turn results in differences in temperature and air pressure around the world, which drives the world’s winds.

As equatorial areas are heated most, the air above them warms and rises as it becomes lighter than the surrounding air, causing an area of low pressure. In cooler areas, the air sinks because it is heavier and results in an area of high pressure. Winds will blow as air is squashed out by the sinking cold air and drawn in under the rising warm air. Any difference in temperature like this will always cause a difference in air pressure, and therefore winds will blow. These movements result in a global wind pattern, with air moving between different areas around the world and also at different heights in the atmosphere. Colder air from the poles tends to sink and move towards the equator closer to the surface of the earth. In contrast, warm air from the equator rises and moves towards the poles high in the atmosphere because it is lighter.

Atmospheric pressure is the force per unit area exerted on a surface by the weight of air above that surface in the atmosphere of earth. The gas molecules of the atmosphere are pulled towards the earth by the force of gravity and hence exert a force on earth surface. In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. Atmospheric pressure influences other weather elements in a significant way. Small changes in air pressure may not be felt, but they are important for bringing a change in weather. Atmospheric pressure can be calculated as the summed weight of all gas molecules between a horizontal plane and top of the atmosphere and divided by the area of the plane. Low pressure areas have less atmospheric mass above their location, whereas high pressure areas have more atmospheric mass above their location.

Measurement of atmospheric pressure

The standard unit of pressure in the SI system is the Pascal which is the name given to one Newton per square metre (N/m²). For meteorological purposes, standard sea-level pressure is 101325 pascal (Pa). To simplify this large number, the millibar unit (mb) has been adopted, which is equal to 100 pascals. Units like kiloPascal (kPa) or hectoPascal (hPa) are also used to measure pressure. 1 kiloPascal is equal to 10 millibars and 1 hPa is 1 millibar. The standard sea-level pressure is represented as 1013.2 mb or hPa.

Soil temperature is an important environmental parameter for plant growth and development. It has direct effects on microbial growth and development, organic matter decay, seed germination, root development, and water and nutrient absorption by roots. In general, the higher the temperature the faster these processes occur. Variation in soil temperature is much more pronounced because of varying characteristics and composition of soil.

The soil gains heat by absorption of solar radiation and longwave counter radiation from the atmosphere, downward transfer of sensible heat and horizontal transfer of heat from the surroundings. On the other hand, soil loses heat by longwave radiation to the atmosphere, upward transfer of sensible heat to air when the soil surface is hotter than air and with evaporation and horizontal transfer of heat from the column to surroundings.

Temperature is the physical property of an object that quantitatively expresses the hotness or coldness. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot. When a heat transfer path between them is open, heat spontaneously flows from bodies of a higher temperature to bodies of lower temperature. If no net heat flow occurs between two objects, the objects have the same temperature which are then said to be in ‘thermal equilibrium’. Temperature plays an important role in all fields of natural and applied sciences. Most of the weather parameters are dependent on it, directly or indirectly. It has important role to play in the development and growth of all living organisms in all stages of their growth.

Atmosphere receives the heat energy from the sun and its temperature increases. Due to different amount of heat energy receipt at different places, the air temperatures at different places also vary. The variation in air temperature basically results into air motion, so as to equalise the energy content of the different regions of the earth. Thus, atmospheric temperature is one of the basic elements of weather and climate.

Sun is the prime source of energy injected into the earth’s atmosphere. The sun is the nearest star to the earth. It is a hot ball of glowing gases at the heart of the solar system. Its radiant energy is practically the only energy source to the earth. Very small and insignificant quantities of energy are available from other sources such as the interior of the earth, the moon, and other stars. Without the sun’s intense energy and heat, there would be no life on earth.

The mean distance of the sun from the earth, also known as one astronomical unit (1 AU), is approximately 1.496 × 10⁸ km, though the distance varies as the earth revolves round the sun in an elliptical orbit. At this average distance, light travels from the sun to earth in about 8 minutes and 19 seconds. The energy of the sunlight supports almost all life on earth by photosynthesis, and drives earth’s climate and weather. The minimum sun-earth distance is about 0.983 AU and the maximum is approximately 1.017 AU. The earth is at its closest point to the sun (perihelion) on around January 3 and at its farthest point (aphelion) on around July 4.

The sun makes up about 99.86% of the mass of the entire solar system. The visible disk or photosphere has a radius of 6.599 × 10⁵ km, and the solar mass is 1.989 × 10³⁰ kg. The sun is a completely gaseous body. The chemical composition (by mass) of the outer layers of sun is 71 per cent hydrogen, 26.5 per cent helium, and 2.5 per cent heavier elements like oxygen, carbon, neon, and iron among others. Since the sun is not a solid body, different parts of the sun rotate at different rates. At the equator, the sun spins once about every 25 earth days, but at its poles the sun rotates once on its axis every 36 days.

The gaseous envelope surrounding the earth is called atmosphere. Thus, atmosphere can be defined as the dynamic layer surrounding the earth above its surface containing various gases, moisture, aerosols, etc. The atmosphere is retained by earth’s gravity.

The atmosphere protects life on earth by absorbing ultraviolet solar radiation, warming the earth’s surface through heat retention and reducing temperature extremes between day and night. The common name given to the atmospheric gases used in breathing and photosynthesis is air. The atmosphere has a mass of about 5.15 × 10¹⁸ kg, three quarters of which is within about 11 km from the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The imaginary ‘Karman line’ lies at an altitude of 100 km above the mean sea level, and commonly represents the boundary between the earth’s atmosphere and outer space. The study of earth’s atmosphere and its processes is called atmospheric science or ‘aerology’. The atmosphere serves the life-system on the earth by the following activities.

Meteorology is derived from the Greek word meteoro which means above the earth’s surface; i.e., the atmosphere. The state of the atmosphere experienced at a given time, in any location on the surface of the earth is known as weather. Thus meteorology is the scientific study of the atmosphere or the weather. It is a branch of physics dealing with atmosphere and it is often quoted as the ‘physics of the lower atmosphere’. The main focus of meteorology is to understand the weather processes and forecast the weather. Solar radiation, the air mass and moisture are the three key ingredients that make up weather. The exchange of heat, moisture and momentum between the earth’s surface and the atmosphere determines the characteristic of weather. The observable weather events are known as meteorological phenomena and are defined by a set of variables called weather elements. Atmospheric temperature, atmospheric pressure, humidity, precipitation, cloudiness, wind and visibility, etc. are examples of such weather elements. The weather elements are not separate entities. They are closely related with each other and are highly variable in nature. Meteorology explains and analyses the changes of these weather elements.

Meteorology

The major subdivisions of meteorology are dynamic meteorology (or atmospheric dynamics) and physical meteorology (or atmospheric physics). The dynamic meteorology is concerned with the analysis and interpretation of the three-dimensional, time-varying, macro scale motions and energy transformations in the atmosphere. The science of dynamic meteorology is meant to develop models based on the hydrodynamic and thermodynamic equations. The physical meteorology is concerned with the processes that alter the physical properties and the chemical composition of air parcels as they move through the atmosphere.

Genetically modified organisms (GMOs) can be defined as organisms in which the genetic material (DNA) has been altered in a way that does not occur naturally. The technology is often called “modern biotechnology” or “gene technology”, sometimes also “recombinant DNA technology” or “genetic engineering”. It allows selected individual genes to be transferred from one organism into another, also between non-related species. Genetically modified (GM) foods are foods derived from genetically modified animals and marines. Genetically modified animals and marines are those in which specific changes introduced into their DNA by genetic engineering using a process of either Cisgenesis or Transgenesis. These techniques are much more precise than mutagenesis where animals and marines are exposed to radiation or chemicals to create a non-specific but stable change. Other techniques by which food animals can be modified are selective breeding and somaclonal variation. By this means desired quality of meat, egg and other animal products can be produced. But it is a common thinking that foods derived from genetically modified animals and marines are far from safe. They are likely to be contaminated by potent vaccines, immune regulators and growth hormones, as well as nucleic acids, viruses and bacteria that have the potential to create pathogens and to trigger cancer.

Organic meat food products are choice products for health conscious people. These are the products produced mainly in most natural way without using fertilizers, pesticides and growth regulators in their feed and fodders. In addition, meat animals are also reared without growth hormones, antibiotics drugs etc. and grazing of the animals is a prerequisite in organic farming system.

The term organic farming was first time used by Lord Northbourne. The term organic farming was derived from his concept of “the farm as organism”. It is a holistic, ecologically balanced approach to farming. In 1991, the European Commission formulated the first government system to regulate organic labelling. In India, standards for organic agriculture were announced in May 2001 and the National Programme on Organic Production (NPOP) is administered under the Ministry of Commerce. The concept of organic meat food products has been emphasized now a day due to animal welfare point of view, consumer’s conscious ness, less residue level of chemicals, antibiotics and drugs, Bovine spongiform encephalopathy (BSE), Foot and mouth disease (FMD), genetically modified food etc.

Organic meat food products as a whole are dependent on the life stages of the livestock like its origin, feeding, housing, health, breeding, transportation and slaughter. The other factors accounting for organic foods are its production, harvesting, preservation and processing. Inspite of low growth rate of organic red meat globally, growth in dairy, egg and poultry is increasing day by day. At present 1.2 million hectares (0.6%) of Indian land is producing organic products (Willer and Kelcher, 2011).

Meat and meat products industry is a sunrise industry in India having huge potential for upliftment of agricultural economy. India is the second largest food producer in world but the contribution of meat industry is still confined to localized handlers. So to uplift industry basic infrastructure, food chains, food security and safety along with standards and laws formulation and their implementations is today’s need. Standards are carefully drawn specifications with respect to a food product. These standards are mainly of three types i.e. government, trade and research standards. Government standards are formulated by the government of India or state government and also have the power to implement these standards while trade standards are implied by the individual company. Research standards are formulated on the basis of comparative study of the products by the researchers. Laws are the legislations enforced by the organisations either government or by autonomous bodies made under the constitutional acts of the country. At present numerous standards and laws are in existence in individual country or at international level. The need is to harmonize them as per the industry and trade requirement.

Domestic Organizations Involved in Standards and Laws Formulation

For the formulation, enforcement and control of standards and legislations at domestic level various organizations are of prime value. Some of these are:

Eggs are considered as Nature’s original functional food because they are abundant source of nutrients like vitamins and minerals. It contains valuable nutrients from the high-quality protein to significant levels of beneficial vitamins, antioxidants and other healthful compounds. The protein of eggs is considered as highest quality protein as compared to other animal protein sources which is readily available and most inexpensive. Eggs are good source of all well balanced nutrients for persons of all age groups. Egg is a unique combination nutrient like it is rich in protein and low in calorie. The nutrients concentration in eggs is dependent on breed, strain, species, feed, age, season, storage and processing methods.

The nutritional value of eggs lies chiefly in their proteins of good biological value; an average-sized egg (60 g) provides approximately 7 g of proteins. These proteins are rich in essential amino acids with a very good balance between these amino acids. So the egg protein can be regarded as a reference protein. On comparison we can say that 2 eggs provide as much protein as 100 g of meat or 100 g of fish. The energy value for an average egg (60 g) is approximately 376 Kj (90 kcal). The lipid content is 7 g, most of these lipids being contained in the yolk. Among the total fatty acids 2/3^rd of these are unsaturated. Egg also contains 180 mg of cholesterol and rich in vitamins (A, D, E) and trace elements (iron and zinc).

Sensory evaluation is a scientific method of evaluating foods including meat products that applies principles of experimental design and statistical analysis through the use of human senses like sight, smell, taste, touch and hearing. It is also called organoleptic evaluation in which we measure, analyse and interpret reactions to those characteristics of materials as they are perceived by the human senses. These attributes can be perceived well by the human sense organs as compared to instruments available for this purpose. It is a fact that no single instrument is able to assess all the attributes of meat products. With the help of these instruments we can very well evaluate the single quality attribute of meat product i.e. shear force instrument or penetrometer is good for knowing the texture and refractometer is for colour interpretation.

Physico-chemical and microbiological quality of meat and aquatic food and food products gives its overall safety and quality status as a food. The physico-chemical and microbiological qualities of raw material have great importance on the product development. It also affects the shelf life of the raw material as well as final product.

Fresh meat is a type of meat which has not been subjected to any processing whereas raw meat is a fresh meat which has undergone freezing. The qualities of fresh meat are important as far as merchandiser, purchaser and consumers are concerned and it is also important for adaptability in further processing. The important quality parameters of fresh meat are:

Formulation of meat and sea food products requires various ingredients which are commonly known as food additives. Food additives are those non-meat ingredients which are used to enhance colour, flavour, aroma and texture of the meat and sea food products. These food products can fulfil the demand of modern consumers. As per the definition of Food and Drug Administration (FDA) food additives are those substance which are used to provide a technical effect in foods. The use of food additives has become more prominent in recent years, due to the increased production of prepared, processed, and convenience foods. Additives are used for flavour and appeal, food preparation and processing, freshness, and safety. These additives can be classified as curing ingredients, extenders and binders, flavour enhancers and other additives. For the formulation of different products both raw materials and ingredients should be of food grade and sound hygienic strength. In the starting of this chapter we will discuss about ingredients used then the specific formulations will be discussed for better understanding of meat and sea food processing.

Curing Ingredients

Curing agents such as salt, phosphate, sugars, nitrite and nitrate, sodium ascorbate and erythorbate etc. have traditionally been used in various meat formulations from long back. The details of these ingredients have already been discussed in chapter-8 of this book. So we will try to discuss other ingredients which are relevant for meat and sea food products other than these ingredients. Cure accelerators such as ascorbates and erythorbates are used to speed the curing process. They also stabilize the colour of the final product. The examples are ascorbic acid, erythorbic acid, sodium erythorbate, citric acid, sodium citrate, sodium acid pyrophosphate, glucono delta lactone (GDL) etc. Glucono-delta-lactone (GDL) acts as a curing accelerator in meat and meat products. It is permissible up to 1% in sausages and up to this level it lowers the pH about 0.5 thus inhibits the growth of spoilage micro-organisms. GDL also facilitate the cured colour development.

Food packaging is an essential technique for preserving food quality and minimizing food wastage. It is a scientific technique of containing food against physical, chemical and microbiological contaminants. In addition package also display the product in most appropriate manner and provide product information to the consumers while at the same time allowing convenient handling and efficient distribution. The packaging of meat and meat products are particularly important because meat is highly nutritious food and provides good medium for the growth of micro-organisms. Meat and meat products are also susceptible to bacterial growth due to their high water activity. Exposure of meat and meat products on atmospheric temperature and sunlight leads to various types of deteriorative changes. For example when cut meat surfaces exposed to ambient air provide excellent breeding grounds for most bacteria. Minced meat is even more at risk due to the large exposed surface area. Packaging provides protection of food against external and internal factors but once food gets deteriorated it can not be controlled by packaging. For this reason rigorous hygiene in all processing and pre-packaging steps is vital for packaging of perishable food items like meat and meat products.

Meat processing is the set of methods and techniques used to bring substantial chemical and physical changes in the natural state of meat. These are the methods which are used for making meat and their products attractive, nutritious and marketable as well as for the prolongation of shelf-life. In processing techniques, grinding, chopping, addition of seasoning, alteration techniques for colour, heat treatments etc. are included but cutting, trimming and deboning are not included in processing operations.

History

Meat processing dates back to the prehistoric ages and probably the first processed meat product was sundried meat. Lator it turns to burning of meat over wood fire while salting and smoking of meat was practiced first time in the time of Homer, 850 B.C. In 63B.C.-14 A.D. at the reign of Augustus honey was tried for preservation of meat. Lator various types of cooking such as roasting, smoking, steaming and oven baking came in existance. Salt-preservation was especially common for foods including meat and meat products for warrior and sailor’s diets, until the introduction of canning methods.

Modern food processing technology in the 19th and 20th century was largely developed to serve military needs. In 1809 Nicolus Appert invented a vacuum bottling technique that would supply food for French troops and this contributed to the development of tinning and then canning by Peter Durand in 1810. Although initially expensive and somewhat hazardous due to the lead used in cans. Canned goods would later become a staple around the world. Pasturization discovered by Louis Pasteur in 1862 was a significant advance in ensuring the micro-biological safety of food. In 20^th century, food processing advances with the development of spray drying, freeze drying and the introduction of artificial sweeteners, colouring agents and preservatives such as sodium benzoate. In late 20^th century ready to eat meat food products were introduced to cater the need of consumers.

Ageing of meat is also known as conditioning or tenderising or ripening or maturing and sometime resolution of rigor. It is a process of holding unprocessed meat above freezing point under controlled conditions. By this process we can make muscle soft and pliable thus meat becomes tender. When we keep the meat above freezing point at temperature between 0-3ºC then all those changes occurs which are normally occurs at higher temperature i.e. atmospheric oxidation and enzymatic action of fat, bacterial action etc. When this temperature range becomes below freezing point then it inhibits completely the enzymatic action in the muscles. Ageing is required for marked increase in flavour, juiciness and tenderness of meat. In this process action of enzymes in meat plays key role while bacterial action is not of any importance. Meat tenderness and taste are definitely improved if carcasses or vacuum packed cuts are conditioned after slaughter but paradoxically beef is quite tender just two hours after slaughter and several days of conditioning are required to recover this degree of tenderness.

During the contraction of muscles, thick and thin filaments sliding to each other and decreases the length of sarcomeres. In turn, this decreases the length of fibrils, fibres and the whole muscle. If these muscles remain in contracted length when rigor develops, it causes massive overlap of thick and thin filaments leading to severe meat toughness. It is also necessary to avoid the cooling of meat too rapidly after slaughter, otherwise it cold-shortens and gets tough. If we avoid cold-shortening of muscles during conditioning, it will increase meat tenderness. But with too much conditioning, weight loss, surface spoilage and the cost of refrigerated storage increases.

Ageing of carcasses with little or no fat cover is not recommended by meat specialists. Because these carcasses loose moisture rapidly, loose weight excessively and discolour the meat surface rapidly. In addition, lean meat is also susceptible to deterioration through microbial growth, slime formation by bacteria and mould growth etc. Ageing is important for beef and buffalo meat while pork and lamb do not require ageing because they are slaughtered in the age where they are young and inherently tender. Additionally, the unsaturated fats found in pork fat oxidize during ageing causes rancidity and off flavour. Veal has very little protective fat covering and is high in moisture; thus it does not lend itself to ageing.

Preservation of foods including meat and aquatic foods is a creation of conditions for the food articles in such a way to stop or greatly slow down the activities of micro-organisms, chemical and enzymatic reactions and physical forces to prevent the meat and aquatic foods from spoilage while maintaining its nutritional value and sensory attributes.

Significance of Meat Preservation

1. Meat and aquatic foods are perishable food items and are very prone to spoilage and rancidity development due to high nutrients, moisture and neutral pH.
2. Once meat and aquatic foods is exposed to microbial contamination, chemical and enzymatic reactions then it will be very difficult to attain asepsis.
3. To enhance the keeping quality of meat and aquatic foods so that it will be available for further processing.
4. It protects meat and aquatic foods from shrinkage, sweeting and other physical forces.
5. To protect human health by providing the wholesome meat and aquatic foods to the consumers.
6. By this way we can minimize utilization of energy in processing of meat and aquatic foods.

Fraudulent substitution of meat is the adulteration or mixing of the inferior or cheaper quality meat into superior quality meat. The first case of fraudulent substitution was recorded in thirteenth century A.D. at Florence in Italy. A common fraud in the meat industry in which uninspected meat is substituted for meat that has undergone inspection and been branded as satisfactory. The other frauds are the substitution of meat of another species, e.g. horse for beef especially in Britain and Ireland, beef in kangaroo meat in Australia, cat for chicken or rabbit, goat meat for mutton, mutton for venison, dog meat and cat meat for chevon in other countries including India. As per an estimate about 25-30% of meat sold in India is adulterated. These practices are more common in comminuted meat products. These illegal practices are punishable under PFA act 1955. The choice of method to be applied is depend on the need or condition of meat recovered.

Meat is an animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat but it may also describe other edible tissues such as organs, livers, skin, brains, bone marrow, kidneys or lungs. Meat is highly nutritious food because it contains protein, fat and carbohydrates in relative proportion, supply energy as required by the human body, posses ability to build or replace tissues and the substances present in meat are easily absorbed by the human body. Meat is also a good source of B-complex vitamins but fat soluble vitamins are low in meat. It is a good source of phosphorous, zinc and iron but low in calcium. Meat also contains significant amount of copper, sodium, potassium and magnesium but low in carbohydrate contents. Carbohydrate is found mainly in form of glycogen which disappears completely after completion of rigor mortis. In general lean red meat is particularly good source of protein, niacin, vitamin B6, vitamin B12, phosphorus, zinc and iron. About 100g of meat can provide more than 25% RDI of these nutrients. It also provides more than 10% RDI of riboflavin, pantothenic acid and selenium. Of the four meats, mutton is particularly nutrient-dense and the richest source of thiamine.

Conversion of muscle to meat is a complex process in which several physical and chemical changes takes place over a period of several hours or even days. The major changes which take place during this process include fall in muscle pH and temperature as well as muscle shortening which further leads to proteolysis or ageing. These changes during conversion of muscles to meat are variable and have great effect on meat quality (tenderness, juiciness, flavour, colour etc.) and also on certain processing characteristics like emulsification, binding properties and yield of the products. To know this complex process it is necessary to understand the process of energy production and metabolic pathway shifting in live animals.

Pre Slaughter

In the living animal, aerobic metabolism is used to obtain energy. The source of energy at this stage is either free fatty acids or blood glucose or muscle glycogen. In this process total 38 ATP molecules are produced from single glucose or glycogen molecule by the complex processes known as glycolysis, oxidative decarboxylation and oxidative phosphorylation. However, under stressful situations, anaerobic metabolism may be used and lactic acid is produced. Lactic acid is usually transported from the muscles to the liver, where it is re-synthesized into glucose and glycogen, or to the heart, where it is metabolized to carbon dioxide and water.

The word meat comes from the old english word mete, which referred to food in general. Most often this means the skeletal muscle and associated fat but it may also describe other edible tissues such as organs, livers, skin, brains, bone marrow, kidneys and lungs etc. In other words we can say meat is those animal tissues which are suitable for use as food by the man. It is composed of numerous types of tissues like muscle tissues, epithelial tissues and nervous tissues but the major component of meat is muscle. Particularly skeletal muscle is the principal source of muscle tissue in meat while smooth muscle contributes little to meat. The muscle and connective tissues are the major compositional components and contributes towards qualitative and quantitative characteristics of meat. Broadly muscle can be classified into striated and smooth muscles. Striated muscles have transverse band pattern as seen in skeletal and cardiac muscle. However, smooth muscles do not show such pattern and mainly found as a component of blood vessels.

In spite of big potential of the largest livestock population in the world, meat industry in India is still in nascent stage. It is a business of those who are not trained and very much literate. The industry is primarily based on the raw material that is not reared for meat purpose but serves the secondary role after passing their viable life in primary field. The industry is also facing problem of social prejudice and meat is taboo for certain communities. But scenario is now changing and people are coming forward to organise the sector. Now the society is accepting the facts that meat is an only source of cheap and nutritious food to million of people in India and the good source of animal protein for large segment of Indian population, particularly landless, small and marginal farmers.

India ranks fifth in the world meat production with the annual meat production of about 6.3 million tones which is 2.21% percent of world meat production. In the last two decades meat industry in India has grown @ 4.5% whereas, during the last five years, this segment has been growing very fast at the rate of 27% annually. It has a good future if given proper attention by the Government and Private Entrepreneurs. In total meat production, share of cattle is 17.34%, buffalo 23.3%, sheep 4.6%, goat 9.4%, pigs 5.3%, poultry 36.6% and others 3.4%. The share of various meat types in total Indian meat production accounts buffalo meat 1.5 million tones, beef 1.28 million tones, mutton 0.24 million tones, chevon 0.53 million tones, pork 0.50 million tones, chicken meat 2.20 million tones and duck meat 0.07 million tones. To produce the above quantities, the extraction or slaughter rates in cattle are about 7.9%, buffaloes 11.1%, sheep 47.9%, goat 37.9%, pigs 88.9% and poultry 73.6%. In the world total meat production Indian cattle meat shares 13.1%, buffalo meat 55.8%, mutton 5.7% and chevon 14.9%. However, India is having world’s 15.0% (210 million) cattle, 57.0 %( 111 million) buffaloes, 7.0 %( 74 million) sheep, 17.0 %( 154 million) goat and 1.5% pigs. Overall contribution of meat sector in total output of Livestock sector was Rs 25984 crores in the year 2004-2005.

In sub-tropical agro-climatic conditions of India, a variety of insect-pest, weeds and diseases hamper the economic growth of field crops. For effective control of these pests, a number of pesticides including insecticides, fungicides, herbicides and nematicides are to be applied. Estimation technique for single pesticideonly can not be followed for detection of residues of all categories of pesticides. Hence, this constantly expanding use of pesticides on food crops accentuates the need for rapid, precise and sensitive method for determination of pesticide residues of all the major groups of pesticides. In such situation, multi-residue analytical technique can be efficiently followed for detection and estimation of multiresidues of intra and inter class xenobiotics.

The purpose of multiresidue analysesistodeterminetheresidues ofas manypesticides as possible withina short period of time even if the recoveries of somecompounds are low. In multiresidue methods the recoveries up to 70% are accepted.The recoveriesless than70%have tobe mentionedspecifically. Multiresidue analysis is relativelymore sensitiveand requires extreme vigilance on the part of the analyst during processingof samples. Additionally, instrument, GLC,need to beequipped withcapillary columnsforhigh resolutionand sophisticated detectorslikeECD, NPDand MSD for detectingmulti-residues of the pesticides. Multiresidue analytical methods/techniques havebeen developed for determination of general pesticide residues for some environmental componentsand differentfood commodities.Criteria formulti-pesticides screening as per California Department of Food and Agriculture (CDFA) are:

Crops treated with pesticides invariably contain small amount of these chemicals and the hazard depends on the amount of pesticide residues that remain on the crop and their toxicity. The amount of residue that may remain on crop or food commodity and environmental commodities depend on the nature of pesticides, good agricultural practice, environmental conditions and adoption of safe waiting periods and other perfect methods of storage. As residues are inevitable by product of pesticide use, hence pesticide residue in food commodities and their entry in to food chain has become major cause of concern all over the world. The plant science industry has a responsibility to assist farmers to produce crops that are acceptable to the food chain and consumers alike.

It is clear that pesticide residues in farm produce should be kept as low as practicable, and eliminated whenever possible through Good Agricultural Practices (GAP). However, the use of pesticides can be regulated to ensure minimum residues on food which can be considered safe to human consumption and environment as a whole.

To regulate pesticide residues to safe levels, a concept was introduced by Joint FAO/WHO Expert Committee on Food Additives (1955) and Codex Alimentarius Commissionwas established in 1964 to implement the Joint FAO/ WHO Food Standard Programmes. The Commission has laid down principles for aiming at the maximum residue limits (Tolerance limits) of pesticide on food commodities. The recommendations are based on:

In the present era, residue analyst is exposed to array of analytical choice and as per International regualtions, presence of pesticide residues in environmental components and food commodities are becoming more stringent.Generally, multiresidue methods are based on GC equipped with selective detection either electron capture detector, nitrogen phosphorous detector, flame ionization detector etc. One most widely applied technique in pesticide residue analysis is HPLC, equipped with different detectors. Another up-datemethod for confirmation is gas chromatography-mass spectrometry(GCMS)and HPLC-MS applyingparticlebeam or thermo sprayionisationtechnique. Recently one more analytical technique which has gained ground in the field of pesticide residue analysis, is high performance thin layer chromatography (HPTLC).The criteria of good analytical technique like simple, rapid, flexible, versatile, inexpensive, easily documented and validated has been the inherent advantage of HPTLC. Strictly speaking, HPTLC is not different in principleor application from conventional TLC, but due to improvements in materials, its effectiveness has also enhanced.The technique has a potential to operate upto femtogramlevel. HPTLC is a sophisticated and automated form of TLC. It is a technique which can generate about 5000 or more theoretical plates. The high performance in TLC is achieved by optimized plate coating materials, by improved sample application techniques, and by developing newmethods for the development of mobile phase. Thus HPTLC is an instrumental approach at different stages of TLC. A flow chart for HPLC principle is shown in Figure 8.1. The principle of separation is based on adsorption and this leads to easyseparationof isomers, includingchiralcompounds.Main difference between HPTLC and TLC is given in Table 8.1

The phenomenon and behavior of supercritical fluid (SCF) has been the subject of research right from 1800's and suggestion of supercritical fluid chromatography (SFC) came in to exixtence in 1958. Supercritical fluid chromatography (SFC) was first developed in 1960, and that time, it was considered as a science fiction chromatography and a revolutionary separation technique. But its reputation has slowly ebbed over the years and it is now moving forward by leaps and bounds as a stable analytical method with many advantages over the existing chromatographic methods. It is an unit operation that exploits the high dissolving power of fluids at temperature and pressurre above their critical values for extracting analytes from sample matrices.The first commercial packed column of SFC was made available in 1981 and the first commercial capillary column SFC instrument was introduced in 1985. Several refrences are useful for understanding the super critical fluid extraction and super critical fluid chromatography

High performance liquid chromatography (HPLC) was developed during late 1960s and early 1970s. Today it is a widely accepted separation technique for both sample analysis and purification in a variety of areas. HPLC, basically a highly improved form of column chromatography and popularly known as liquid chromatography, like other forms of chromatography, whether paper, thin layer or gas chromatography, needs two essential components, the stationary and the mobile phase. It has the unique ability to separate and quantitate residues of polar, non volatile and heat labile chemical compounds. HPLC uses high pressure pumps up to 400 atmospheres that makes it much faster, short and narrow columns packed with micro particulate phase and a detector. To affect a separation, mixture to be analysed is dissolved in a solvent (ideally this solvent is identical to mobile phase) and then forced to flow through analytical column along with mobile phase. In the column the constituents of mixture get resolved and are detected with a suitable detector by a proper choice of column, mobile phase and detector. HPLC is a technique having high degree of versatility. There are several excellent texts published over the last decade which may be consulted for general information on the instrumentation in liquid chromatography

Chromatography was first employed by Ramsay (1905) to separate mixtures of gases and vapours. The first scientist to recognize chromatography as an efficient method of separation was the Russian botanist Tswett (1906), who used a simple form of liquid-solid chromatography to separate a number of plant pigments. The colored bands he produced on the adsorbent bed evoked the term chromatography for this type of separation (color writing).Althoughcolor haslittletodo with modern chromatography, the name has persisted and, despite its irrelevance, is still used for all separation techniques that employs the essential requisites for a chromatographic separation,viz. a mobile phase and a stationary phase.

Gas-liquid chromatography (GC) was invented by James and Martin (1952) and is a separation technique in which the mobile phase is a gas (usually helium or nitrogen) and the stationary phase is a liquid. In the original columns used by James and Martin, the liquid stationary phase was adsorbed on the surface of an inert support such as Celite (a diatomateous earth) or calcined Celite (a form of brick dust). The support was usually deactivated before use by acid treatment and subsequent reaction with hexamethyldisilazane. The technique was extensively used for the separation of a wide range of volatile substances. Thus, chromatography has been defined as a separation process that is achieved by distributing the components of a mixture between two phases, a stationary phase and a mobile phase. Those components held preferentially in the stationary phase are retained longer in the system than those that are distributed selectively in the mobile phase. As a consequence, solutes are eluted from the system as local concentrations in the mobile phase in the order of their increasing distribution coefficients with respect to the stationary phase.By separating the sample into individual components, it is easier to identify (qualitate) and measure the amount (quantitate) of the various sample components.

Chromatography is an important analytical technique for the separation, isolation and identification of the constituents of a mixture. It is a physical method of separation in which the components to be separated are distributed between two phases; one of these phases consisting a stationary bed of large surface area, the other being a fluid that percolates through or along the stationary bed. All forms of chromatography do have the common features given in this definition. All of them involve the physical movements of the sample across a flat surface (tube like) or through a tube. The stationary phases in all of these possess a large surface area. In all the techniques, the movement of the sample is due to the motion of the fluid/mobile phase. The principle underlying all these methods is the selective retardation of the movement of the components by the stationary phase. These methods result in the production of bands of concentrated components. The basis of naming various chromatographic methods are different:

After having performed their function, pesticides in the parent form or in some converted form reach the soil, the ultimate sink for these moieties which are collectively termed as residues. According to FAO 1986, pesticide residue is defined as any substance or mixture of substances in food, agricultural commodities or animal feed resulting from the use of pesticides and includes any specified derivatives such as degradation products, metabolism, reaction products and impurities that are considered to be of toxicological significance. From the soil they move into other segments of the environment. The pesticide residues are absorbed by plants and enter the food chain, where they get concentrated in animal fat. Some residues are carried away by wind in the vapor form, which enables them to be transported to long distances from the source of application and then get collected by dust and rain before they are deposited on the ground again. Pesticide residues also move to aquatic environments through runoff, leaching, and atmosphere disposition.

The knowledge on the fate of pesticides, after application in the environment is useful to research workers associated with their safe and effective use. It is important to know whether a xenobioticwillpersist orwill be inactivated. Frequently persistence is desirable for sustained control. However, for many cases, rapid detoxificationof the compound may be required to avoid cumulative effects. Most of the pesticides are not very soluble in water andtheir oxidation orhydrolysis (or both)leads to formation of polar groups. Such reactions are called primary metabolic reactions, often, but not always. Theproducts ofthese primary reactions undergo secondary changes whereby they are conjugated with endogenous substances to form molecules that are more readily excreted. In higher animals, these changes facilitate the transportation of metabolites of pesticides in blood, which in turn leads to their eventual excretion.

Part A

1. Pesticides

A pesticideis defined as anysubstance intended for preventing, destroying, attracting, repelling or controlling pests including unwanted species of plant, or animals duringthe production, storage,transportation, distributionand processing of the food, agricultural commodities or animal's feed or which may be administered to the animals for the control of ectoparasites. Pesticides include insecticides, herbicides, fungicides, acaricides, nematicides, etc.

According to food and agricultural organization (FAO) 1986, the term pesticidehas been defined as“any substance or mixture of substances intended for preventing or controlling any pest and includes anysubstance or mixture of substances intended for use as plant growth regulator (PGR), defoliant or desiccant. The term excludes fertilizers and antibiotics or other chemicals administered to animals to stimulate their growth or to modify their reproductive behaviour”. Pesticides are the largest group of poisonous substances that are widely broadcast today.

10.1 Introduction

The following plants have been worked out in the laboratory of Prof. N. Raaman: Cynodon dactylon, Artemisia pallens, Leptadenia reticulata, Clausena dentata, Tylophora indica, Aristolochia bracteolata, A. indica, Cissus quadrangularis, Hypericum mysorense. and Solanum trilobatum. Out of some of the data of these plants have been included in the previous chapters. In this chapter, compound isolation (CD1) from Clausena dentata (worked by Dr. R. Kamaraj) and characterization of the compound are given in detail.

10.2 Preparation of extracts from Clausena dentata

The dry powder of stem bark (2.5 kg) was first soaked, at room temperature, in hexane (1:4 w/v) for 24 h. The extract was suction filtered using Whatmann filter paper. This is repeated for two more days and similar extracts were pooled together and concentrated at 40°C under reduced pressure using Buchi R - 153 Rotavapor. The residual plant material was extracted successively with chloroform and methanol in the same manner as followed for hexane. All the concentrates were subjected to column chromatography to isolate the active principles.

9.1 Introduction

Phytochemicals are the individual chemicals from which the plants are made. Phytochemical is simply a word that means plant chemicals. Plants have the ability to synthesize mixtures of structurally diverse bioactive compounds with multiple and mutually potential therapeutic effects. The plants have the capacity of manufacturing the secondary products. Phytochemicals with antioxidant properties tend to be brightly colored because they contain chromophores, ie, a series of alternating single-bonded and double-bonded carbons. Isoprene is often the building block of such units. The darkest green vegetables contain the most chlorophyll, and vegetables with the most chlorophyll require the most antioxidants. Green will mask the other colors, when other-colored antioxidant phytochemicals are present. Hundreds of phytochemicals are currently being studied. Many are believed to have a major positive impact on human health (Duke and Sternberg, 2005). Important plant secondary metabolites have been isolated over a period of time from natural sources. The phytochemical may belong to the following categories : Terpenoids, Phenolic compounds, Alkaloids, Glycosides, Carbohydrates, Lipids, Proteins, Nucleic acids, etc. Some of the phytochemicals from the plants are listed in Table 9.1 and structures of some of them are given in Fig.9.1.