eChapters

Abstract

The tsunami has struck many coastal countries of South Asia on 26 December 2004 and caused greater devastation along Andaman - Nicobar and Indian coasts. In India, Tamil Nadu coast is worst affected in Kanyakumari, Nagapattinam and Cuddalore districts. Subsequently, damage assessment, in respect of natural and physical resources, was done using Remote Sensing and GIS in parts of Cuddalore and Pondicherry coasts. The structural damages were studied village wise and categorized as maximum, moderate and least affected areas. As far as the natural resources are concerned, the changes in geomorphology, land use/ land cover, soil and water have been studied. On the basis of the same, the risk maps were also generated in GIS environment.

Keywords: Tsunami, Damage Assessment, Remote Sensing, GIS, Cuddalore, Pondicherry

Abstract

Geomatics (Remote Sensing and GIS) based tsunami damage assessment was carried out for Nagapattinam coast as a part of All India Coordinated Programme of NRDMS, Department of Science and Technology, New Delhi. The paper discusses the methodology and the inferences made for Nagapattinam region, Sirkali block and north Poigainallur panchayat village, holistically for the former and as case studies for the latter two. The regional studies show that the coastal geomorphology has played a significant role in tutoring the tsunami inundation and the damages with beach, dunes, tidal flats, backwaters and rivers / streams facilitating the inundation of tsunami. The studies in Sirkali block show the similar role of geomorphology, but the damage assessment carried out for Water bodies, soil and ground water show appreciable damage to Aquifer in the form of saltwater mixing / intrusion due to tsunami. Detailed geospatial data bases were generated village wise too. On the basis of the studies, possible remedial strategies were also suggested.

Keywords: Remote Sensing, GIS, Tsunami 2004, Damage Assessment, Tsunami mitigation, Nagapattinam.

Abstract

The damages caused by the tsunami surge of 26, December 2004 could not be recuperated. There is no second opinion for the above statement as attested by the consequences of tsunami surge on the coastal landforms, human lives, properties, biological assets, etc., The attempt made to evaluate the damages caused by the tsunami surge along the study area divulges various factors regarding the response of the coastal environment to this weird phenomenon. Kanyakumari district witnessed the tidal inundation of 50 – 450 m, the least along Colachel and the maximum in Kanyakumari and Muttom coasts. Run-up elevations were seen even up to 6 m in Manakudi and Colachel coasts. In major parts, the beaches of the study area had endured lofty erosion of beach sediments. High occurrence of Casualty was reported in the Coasts of Colachel, Kotilpadu, Manakudi and Azhikkal. Similarly, loss of man-made structures were also observed to be high along the Coast of Manakudi, Colachel, Kotilpadu, Azhikkal and Muttom. Costly articles like boats, fishing nets, etc., were also damaged in Kanyakumari, Pallam, Muttom, Kadiapatanam, Kesavanputhenthurai and Colachel. The quality of water has also been found to be affected with high level of pH and TDS in the coasts of Manakudi and Colachel. Such Colossal damages in the area is attributed to its geo-position exactly at the receiving point of the diverted tsunami surge by Sri Lanka. Bathymetry also seems to have played a crucial role in determining the intensity and angle of the seismic wave propagation in the area.

Keywords: Tsunami, India, Damages in Kanyakumari, Evaluation, Map, GIS.

Abstract

The seaquake on 26^th December 2004 with its epicenter at Sumatra triggered a tsunami, which had a major impact on South East Asian countries. During that incident, the average height of the tsunami wave was 7-10 m and the penetration of seawater was up to 1-1.5 km. The surface water resources meant for irrigation and other drinking purposes got affected by the ingress of seawater in many areas. The direct environmental impacts of the tsunami have more impact along the entire east coast and caused more damages in coastal systems. The physical and chemical perturbations caused in the coastal zone by the tidal waves are discussed. In order to assess the environmental impact on coastal system, it is suggested that significant physical and biogeochemical factors could be framed to quantify the problems.

Keywords: Tsunami, Physical and Chemical Alterations, Coastal zone.

Abstract

The Car Nicobar Island is one of the several islands in Indian Ocean which was severally damaged by the Great tsunami on 26 December 2004. The great tsunami event caused massive devastation, in the form of loss of life and property in south and south East Asia. The objectives of the study are to assess the changes in the coastal features of the Car Nicobar Island using various indicators such as the tsunami height, run- up elevation, water flow direction, erosion, sand deposition and coastal subsidence. Andaman &Nicobar Islands are the summit of the submarine mountain range lying along the great tectonic suture zone extending from Eastern Himalaya to Sumatra and Lesser Sunda via Myanmar border and Arakan hills. The IRS P-6 satellite data has been found to be very useful in the present tsunami assessment studies. The digital analysis of the satellite data was done using the image processing software (ERDAS IMAGINE 8.4) and DTM to quantify the tsunami height (15 m), run up elevation (2-19 m), inundation (295-1203 m) and coastal responses. The settlements and coconut plantations have been severely damaged in the island, which were assessed using GIS analysis of the pre and post-tsunami satellite data.

Keywords: Tsunami, Wave Height, Run-up Elevation, Inundation, Coastal Responses, Remote Sensing, GIS.

Abstract

Coral reefs, the marine representatives of tropical forests, coupled with the sea grasses contribute considerably to the coastal productivity. Damages to these ecosystems will immediately affect the fishery productivity of the region. Due to this, the long-term ecological impact of the recent tsunami will be a serious set back to the local, national and regional economy than the immediate losses. Andaman and Nicobar reefs represent the second largest coral reef formation next to the Great Barrier Reef and are also comparable to the coral reefs of Indonesia and Philippines in terms of diversity of species and associated floral and faunal components. The recent mega – subduction of the Indian plate below the Burmese micro – plate in Andaman – Sumatra region has not only deepened the southern and uplifted the northern group of Andaman – Nicobar islands but also created a disastrous tsunami on Dec 26, 2004. While such tectonic changes are expected to cause longterm changes in the coral reefs of Andaman, Nicobar group of islands, the tsunami has damaged the coral reefs instantaneously. However, the coral reefs of the Gulf of Mannar and Palk Bay are not much affected by the tsunami by virtue of their geographic position in the shadow region of Sri Lanka.

Keywords: Indian coral reefs, Tsunami effect, Coral recovery

Abstract

The mangrove wetlands form dynamic ecotones between land and sea. Mangrove wetlands are unique in terms of environment, plant and animal communities and their distribution is restricted in tropical and subtropical coastlines. They perform a number of protective and productive functions, which ensures ecological and livelihood security to the coastal communities. The role of mangroves in mitigating the impact of cyclones and storm surges is well known but only limited information is available on their role in reducing the impact of tsunami. The Pichavaram mangroves, located on the southeast coast of India in Tamil Nadu, which was hit by the 26 December 2004 tsunami, provided opportunities to understand the contribution of it in tsunami mitigation. Through a systematic field study, a comparative analysis was made on the impact of tsunami in a set of villages, one was protected by mangroves and the other lacks any vegetation surrounding it. These villages are located at more or less equal distance from the sea and situated at about same elevation. Assessment carried out with well defined indicators such as loss of lives due to forceful entry of tsunami water, damages to houses and types of houses, etc., shows that loss of lives and damage to houses were much less in the village surrounded by Pichavaram mangroves. Thus, Pichavaram mangrove wetland, which was restored with the participation of the local community, Tamil Nadu Forest Department and M.S.Swaminathan Research Foundation (MSSRF) during 1993-2004 provided great dividend during tsunami. This underlines the importance of strengthening the ecological foundation of the coastal zone with mangroves and other vegetation as one of the strategies for mitigating the impact of natural disasters in the coastal areas.

Keywords: Mangroves, Natural Disasters, Tsunami, Impact Reduction and Pichavaram.

Abstract

Ennore is an industrial region having many industries on chemicals, fertilizers, refineries etc., discharging their effluents into the Buckingham canal. Present study focuses on the impact of tsunami on water quality of Buckingham Canal segment found to the north of Chennai city, Tamil Nadu, India, in addition to the human interferences. Water samples were collected from surface and near bottom at five locations covering about 20km stretch of the Buckingham Canal during high tide on the spring tide day before (December 2004) and after (January 2005) the mega tsunami. Various water quality parameters measured were pH, Temperature, Salinity, Dissolved Oxygen, Suspended Particulate Matter, Nutrients and Chlorophyll. The maximum depth observed in the canal was 2.5m in December, whereas a shallow depth of less than 0.5m was recorded in January. The water quality analyses confirmed the incursion of saline water (upto 32ppt) into the Canal. Not much variations were observed in Dissolved Oxygen and pH. Because of the organic pollution in the canal, the water was rich in nutrients before tsunami, whereas due to the large quantity of seawater invasion, dilution had occurred after tsunami. High turbidity was observed in January 2005 indicating the tsunami induced disturbance and resuspension of the sediments from sea bed.

Keywords: Tsunami, Ennore, Tamil Nadu, Buckingham Canal.

Abstract

Tsunami (2004), that struck the Tamil Nadu coast has left deep marks in the minds of the affected society. The interview conducted in the coastal villages of the tsunami affected Nagapattinam has brought out many salient societal issues like, loss of leadership, widow hood, debt grip, psychological depression etc, which warrant deeper look to bring them out from the syndrome.

Keywords: Tsunami (2004), Social issues, Nagapattinam, India

INTRODUCTION

The damages caused by tsunami (2004) along the coastlines of most of the South Asian countries are indelible not only from the minds of the coastal population but also from the heart of the entire humanity. The worst affected in the disaster are the fishing community. Many of their mechanized and un-mechanized boats and catamarans were converted to useless debris and garbages by the heartless tsunami. When their settlements themselves were swallowed even with out chewing, nothing to talk about their fishing nets which were just blown off by the ferocious tsunami. In addition, the infrastructure facilities like roads, communication systems, water and power supply were also incalculably damaged. Next to fishermen community, the affected souls were the farmers whose cultivable lands were turned into marine wet lands with swimming and tossing fishes. The Indian subcontinent was facing such onslaughts of various natural disasters periodically but our morale always stood by our side prohibiting us declaring them as national calamities for getting international aids. Specifically in this case, the central and state governments, NGOs and Voluntary Organizations have risen phenomenally to help the affected who were in need. Despite best efforts taken to provide relief and rehabilitation to the affected people, the tsunami has seedled some societal issues / syndrome, which may take long years to settle; it may not settle too. The paper discusses some of such issues gulled out through the interview conducted amongst various cross sections of the affected community.

Abstract

During natural disasters, mostly panic and curiosity lead to greater causalities. But the tsunami is such a disaster which no one have witnessed during their life time nor heard of from their ancestors. On 26, December 2004, tsunami has struck all of a sudden many South Asian coasts including the east coast of Tamil Nadu and Andhra Pradesh causing greater devastation and causalities. This historical event has taught us many lessons and the paper deals with some aspects related to tsunami from the citizen’s view point.

Keywords: Natural calamities, Tsunami mechanisms, Mitigation strategies, Citizen’s perspective.

INTRODUCTION

The tsunami that ravaged the coasts of South India had left tell tale signs that affirm the need for early warning systems as well as well-planned mitigation measures for the benefit of the affected. Over the last 12 months, since the tsunami struck the east coast of India on 26 Dec. 2004, numerous seminars, discussions, programmes and project proposals have been deliberated on various aspects that deserve attention. Government agencies, self-help groups and non-governmental organizations (NGOs) have done commendable post-tsunami work. All sections of the society have responded both emotionally and rationally to the event in an unprecedented manner. In retrospect, to the informed citizen – one who has heard about the event, read about it and discussed it with others, though not have had the ‘experience’ of the natural disaster by himself / herself - what do all these mean ? the tragedy and its aftermath. This paper documents the issues that a citizen would like to ponder over so as to understand the various dimensions of the post-tsunami activities and draw a few lessons that the tragedy had taught us. The major issues pertain to (i) the mechanisms (ii) the coastal vulnerability and the need for assessment (iii) mitigation strategies (iv) media exposition (v) communication networking and (vi) educational facilitation.

Abstract

The paper deals with the roles played by the NGO’s in the relief and rescue phase of Dec, 2004 tsunami and the effective role played by NCRC -NGO Coordination and Research Centre - in the rehabilitation phase along Tamil Nadu coast by creating successful partnership with government and the public.

Keywords: The Role of NGO’s, Tsunami 2004, Relief and Rehabilitation, NGO Coordination Research Centre.

INTRODUCTION

The scale of the tsunami disaster was unprecedented and the response too was out of the ordinary. Tamil Nadu was the worst affected state in India with Nagapattinam district being the most affected with over 6000 lives lost, about 40,000 houses damaged or destroyed and 1.96 lakh people affected. Relief poured in from both government and non-governmental organizations, including the religious organizations, and the first few days witnessed heartwarming outpourings of help and support.

There were about 400 NGOs and an equal number of volunteers to help in the relief operations which included food, clothing, household utensils and bedding. With such a large scale of external support, mainly from organizations and people from outside Nagapattinam, it was not surprising that chaos and confusion marked the first few days of relief operations still. Based on the experience of some professionals experienced in disaster management, a coordination platform was created called the NGO Coordination Cell. This platform was managed by two NGOs, who had long standing field presence in Nagapattinam, viz., South Indian Federation of Fishermen Societies and SNEHA, with the mandate and support of the District Administration. The main role of this platform was to meet the field based requirements of all the relief camps with the resources and materials available with the NGOs and the Govt. The paper briefly deals with challenges faced by the NGO’s in relief and Rehabilitation of the historical Dec 2004, Tsunami.

Abstract

Though people belonging to different disciplines from the common citizen to top level administrators are familiar with cyclones, floods, earthquakes, landslides, droughts, etc., the tsunami which struck and devastated over 1000 km long Tamil Nadu coast was not only unexpected but also an unknown phenomenon for the people of this part of the region. The Government of Tamil Nadu, though faced with this disaster for the first time, has efficiently managed the crisis owing to clear policy directions from the top political executive of the government, the planned working of the ministers, the committed service rendered by the senior officials and the tireless efforts of district collectors and their supporting staff down the line. The immediate measures taken in search, rescue and relief operations are detailed in this paper. Also covered are the rehabilitation measures undertaken including those for orphaned children and unmarried girls and the steps adopted for the prevention of epidemics.

Keywords: Tsunami Disaster, State Administration, Relief and Rehabilitation, Tamil Nadu.

INTRODUCTION

India is traditionally vulnerable to natural disasters on account of its geo-climatic conditions. Floods, droughts, cyclones, earthquakes and landslides have been occurring regularly in some part of the country or the other. In Tamil Nadu, the unprecedented drought in 2002-03, followed by another drought of comparatively less severity in 2003-04 and the floods in the northern coastal districts in October-November, 2004 had kept the State machinery on constant alert. But the tsunami that struck the coastal districts on 26^th December, 2004 was an altogether new and nightmarish experience. It was a disaster, the like of which, had not been seen before. The suddenness and the ferocity with which the waves gushed into the habitations along the 1076 km long coast line, taking the people totally unaware, caused unprecedented damage, death and destruction and posed the greatest challenge to the State administration. However, the state faced the challenge successfully, thanks to the vision and commitment shown by the Government and the timely help rendered by a number of non-governmental organisations and groups.

Abstract

Subsequent to December 26^th 2004 historical Tsunami, The Government of India has conceived a master plan for setting up Tsunami Warning System (TWS) similar to Pacific Ocean Tsunami Warning System. Concurrently, the union Govt has also initiated scientific studies through Department of Science and Technology and the significant amongst these are the

• All India Co-ordinated Programme on Tsunami disaster and risk assessment using GIS technology and
• Bilateral programme with Norway to know the know – how and capacity building in the fields of Landslides and Tsunami

As a part of this bilateral mission, the authors visited institutions connected to Geohazards and Tsunami affected areas of Norway. The article briefly narrates the salient inferences on the Tsunami scenario and the related studies in Norway.

Keywords: Landslides triggered tsunamis, Norway

Abstract

Drying is a widely used method of food preservation. It leads to some structural changes in the dried material resulting in poor quality and rehydration. Freeze drying, though a costly process, reduces water activity without exposing the food material to high temperatures, eventually retains the original quality to a great deal. Moisture in the foods is frozen to ice which is sublimated under low pressure. Low pressure helps to vaporise the ice without transforming it to liquid, hence leaving the food structure porous in nature. The food is claimed to preserve the nutritional, sensory and re-constitutional qualities.

1.1 INTRODUCTION

Most food materials are composed of a very high percentage of water, which can be as high as 95%, and this makes them susceptible to microbial activity. Microbial activity spoils the products, leaving them useless for human consumption. It not only changes their taste and color but it may also develop toxins, thus making them unsafe. There are various methods for preserving food but in order to make them shelf stable, removing water from foods helps keep them from spoiling for a longer period of time.

Abstract

Drying is one of the most important industrial operations for preservation of food material. Due to the major limitations posed by convective drying methods, there is always a need for novel drying techniques which are technically, economically and environmentally sustainable. Based on the principle of moisture diffusion due to vapor pressure gradient, atmospheric freeze drying (AFD) offers a promising alternative to conventional drying systems. A cold gas with low water vapor pressure is used as drying medium to sublimate moisture directly from the frozen material at atmospheric pressure conditions. As a result the product gets dried at much lower temperature unlike convective drying. Thus, products dried with AFD retain better nutrition, texture and color and the process is also considerably cost effective. Major limitation of the AFD process is longer drying time, which can however be accelerated by using heat pump drying or new ultrasound technology. This chapter focuses on mechanism, benefits, limitations and comparative study of AFD with other drying methods such as hot air drying and vacuum freeze drying. It provides an insight regarding effect of AFD on properties of food material based on various studies reported in literature.

Abstract

Multiflash drying (MFD) process is based on the application of multiple cycles of heatingvacuum pulse to a solid food. Heat can be provided by convection (from hot air), conduction (by contact with a hot surface), microwaves, or by a combination of these methods. Due to the moderate temperatures applied to the drying food, and the sudden decompression step (vacuum pulse), MFD processes allow obtaining crispyanddried foods with very good nutritional and sensory properties. Vacuum pulses cause food texturization, which depends on the pressure drop rate during decompression. In fact, the dried products are similar to freezedried foods, but with more open structures, which result in higher crispness. The dehydration can be performed in relatively short processing times, when compared with traditional drying processes (e.g. solar drying, airdrying, vacuum drying and freezedrying). The short process time indicates clearly that this class of drying process presents a huge potential to the production of driedandcrisp foods at industrial scale.

Abstract

Airflow drying persists as the main dehydration operation. Indeed, the high expense of freeze-drying in term of equipment cost and energy consumption considerably restricts its use and confines its applications to high added value products (pharmaceutical products, cosmetics, etc.). However, airflow drying undergoes fundamental problems such as low operation performance, poor product quality and short reliability of the equipment. The time of drying is long; particularly at the end of the operation, which implies crucial energy consumption. The poor quality of the end product is related to thermal degradation and in particular to the compactness of texture as a result of the phenomena of shrinkage and case hardening. Another main problem common to all drying operations, including freeze-drying, is the safety of the end products. Swell-drying is defined as an operation that combines optimized hot air drying with instant controlled pressure controlled texturing. The improvement of texture, the preservation of sensory and nutritional quality, the possibility of manufacturing expanded granule powders and the reduction of drying time and energy consumption allow considering swell-drying as the most relevant drying process.

Abstract

This chapter presents the principle of fluidisation and its use in drying of food materials. Being a convective drying process, capacity and kinetics are limited by process conditions and material properties. The influences are discussed as well as presenting the main equations that describe drying in fluidised beds. The main focus lies on hot gas drying, additionally superheated steam drying as well as atmospheric fluidised bed freeze drying and microwave-assisted fluidised bed drying are presented and discussed.

Abstract

Increasing global demand for ‘fresh-like’ processed food products has forced food industries to investigate into various minimal processing techniques. Food processing in general has been associated with thermal processing, alone or in various combination with chemical and mechanical preservation and processing methods. However, thermal processing methods are energy intensive in nature and tend to reduce product quality and freshness at the cost of shelf-life gain. Advance technique such as microwave, radio-frequency and freeze drying do maintain the product quality but their implementation at industrial scale involves high operational and maintenance cost. An ideal processing method therefore would be one that can process food products without losing its quality, is energy efficient and is easily scalable. In this chapter, we discuss about ‘Electrohydrodynamic (EHD) Drying’, which is can be classified as a minimal processing technique. The heat and mass transfer principles involved in EHD drying have been extensively discussed and so has been the key consideration for designing an EHD drying system.

Abstract

Pulse combustors provide an advantageous superposition of unsteady gas flow and high intensity sound waves. Such a combination does not only accelerate drying rates because of increased heat and mass transfer but also allows processing of liquids, pastes and agglomerated solids in a dispersed state due to aerodynamic impact from the high intensity sound wave. Over last decades, applications of pulse combustion in drying have been exploited continuously and different pulse combustion dryers have been designed and fabricated. In pilot tests and technical reports on these dryers, short drying time, high energy efficiency and product quality are generally reported, which cause that pulse combustion drying is regarded as a technology of the future in convective drying.

This chapter attempt to introduce basic knowledge and state-of the art about this emerging technology and summarizes some recent studies in pulse combustion drying and equipment design. Following a concise description of pulse combustion and pulse combustor, the basic types of pulse-combustion dryers are presented, including spray dryers, fluidized bed dryers, impinging dryers, and dryers of special design. The existing commercial applications and pilot test projects are described and potential applications are identified.

Abstract

Foam Mat Drying (FMD) is an economical alternative to drum, spray and freeze-drying for the production of food powders. The raw material is converted into stable foam by adding foaming agent through beating or whipping in presence or not of foam stabilizers, and dehydrated by different classical airflow and thermal means. A high-quality food powder attributes can be obtained by the proper selection of foaming method, foaming agents, foam stabilizers, time taken for foaming, suitable drying method and temperature. FMD can be used for large production of food powders because of its suitability for all types of food materials, rapid drying at lower temperature, retention of nutritive value and bioactive compounds, good reconstitution characteristics and flowability and cost-effective for producing powders.

In this chapter, basics of foam and its structure, mechanisms of foaming, types of foaming agents and stabilizers for the production of stable foam have been discussed. The influence of foaming agents, foaming properties, thickness of foam and drying temperature on the drying characteristics of mat are also studied. This chapter analyzes the application of foam drying process for different food materials, the microstructure and whole quality attributes of obtained powder, and the energy consumption and costs of FMD as well.

Abstract

Application of ultrasound is one of the most promising uses of novel technologies in food processing. Use of ultrasound at various stages of drying has resulted in significant decrease in drying time and improvement in quality characteristics of dried products. The chapter discusses the principle behind use of ultrasound, general application in food industry with detailed description of various drying processes and equipments assisted by ultrasound.

Abstract

Cocoa and coffee are highly sought after commodity crops in the market owing to the distinct flavor and aroma characteristics. Cocoa beans are mostly used in the manufacturing of chocolates and various types of confectioneries while coffee is mainly consumed in the form of beverages. Both cocoa and coffee need to be dried and roasted in order to produce the flavor precursors which further develop into the desired flavor and aroma in the finished products. This chapter aims to provide an overview of cocoa and coffee processing with particular emphasis on drying and roasting aspects and its impact on product quality.

Abstract

Mushrooms are the fruiting bodies of fungi, a group of organism that is different from fruits and vegetables. They are a rich source of good quality protein having more essential amino acids and vitamins with low calories. There are about six commonly known edible mushrooms throughout the world with button mushroom (Agaricus bisporous) being the most familiar and commercially important variety. Mushroom is a highly perishable product with a shelf life limiting to a few days. Soon after harvest, it starts to undergo physiological disorders like shriveling, wilting, liquefaction, browning, textural as well as weight losses and flavour changes. The main responsible factors for the quality deterioration after harvest are respiration rate, browning, bacterial spoilage of mushrooms, temperature and relative humidity. Because of its limited shelf life under ambient conditions of temperature and humidity, the preservation of mushrooms is a matter of concern. Various techniques have been involved in the extension of shelf life of mushrooms including chemical treatments, cooling, modified and controlled atmospheric storage, radiation, drying etc. Drying is one of the most accepted and effective methods for the long term storage of mushrooms. Mushrooms preserved by drying have a pleasant flavour and are used as an important ingredient in several food formulations including salads, instant soups, meats and rice dishes. Various drying processes like sun drying, hot air drying, freeze drying, vacuum drying etc. can be used for the long term storage of mushrooms. As mushrooms are sensitive to temperature, determining the right drying method is the key for the successful and effective operation of the system. The different operating conditions involved in various methods of drying affect product quality considerably. The effect of drying methods on the process and the quality of the dried mushroom is explained in detail in this chapter.

Abstract

Vitamin C is one of the most important phytochemicals and can be found in almost all fruits and vegetables. Since it covers almost all eventualities, being water solute and prone to leaching from cells, thermally labile (one of the most labile vitamins), pH-, metal ion-, light-sensitive, as well as readily oxidizable by ascorbic acid oxidase, vitamin C is selected as the most frequently measured nutrient to evaluate the nutrients loss during thermal processing. It is generally accepted that if vitamin C is well preserved, the other nutrients are also well retained. Higher retention of vitamin C in processed products is highly desired. Herein this chapter reviews the degradation mechanism and kinetics of vitamin C of fruits and vegetables during thermal processing, such as blanching, drying, cooking and frying. It starts with an overview of the functions of vitamin C in human’s health. Then the current status for understanding of the degradation kinetics of vitamin C during thermal processing was outlined, followed by the discussion of its degradation mechanism. At last, potential strategies or alternatives to keep vitamin C are identified and discussed.

Abstract

Design, operation and optimization of dryers demands the calculation of energy consumption, in most cases in the form of thermal energy, equipment sizing, temperature and moisture distribution of solids as well as temperature and humidity distribution of drying air. Energy calculations are very important as drying is a widespread process in a variety of industries and is highly energy demanding. In the energy analysis of the process the first step is the estimation of the minimum energy requirement followed by the estimation of energy rejection through solids stream and especially through drying air. Increase of thermal efficiency is always willing and the two most common ways for its achievement is the application of heat exchange between cold feeding air and relatively hot rejecting drying air and hot air recirculation. The later is also employed for the adjustment of air temperature and humidity gradient through the dryer. The combination of a heat pump with the dryer decreases considerably the thermal energy consumption but demands electricity and the method can be beneficial in cases of excess electricity production in the process plant, e.g. by cogeneration. Utilization of exhaust hot air from the main drying unit for the predrying of wet solids can also decrease the total energy requirement. The application of humidity adsorption from the feed air increases its drying potential, but regeneration of adsorbent is required. Grand composite curve of the process plant can reveal potential heat sources from different unit operations.

Abstract

The increasing interest in polyphenolic compounds in industries has led to the exploration and exploitation of rich bio-compounds from natural sources, essentially plants and their by-products. Solid-liquid extraction is mostly applied for the recovery of these valuable compounds from plants. Since the extraction process is often difficult in a fresh matrix, a drying operation is needed to reduce the moisture content, and preserve the targeted valuable compounds. An uncontrolled drying operation will lead to product damage and hence, loss in quality, reason why, several studies have been carried out to understand and control the drying process. The present chapter aims to present some data on drying for bioactive compound recovery from plants and their by-products, mainly polyphenolic compounds. Our main interest is the mathematical tools used to model the drying process.

1.1. Introduction

The significance of milk as the most wholesome single food available in nature has never been debated. It is as ancient as mankind itself, as it is the substance created to feed the mammalian infant. All species of mammals, from the lowly rat to the mighty whale, produce milk for this purpose. Several centuries ago, perhaps as early as 6000-8000 BC, ancient man learned to domesticate species of animals for obtaining their milk for consumption. These included cows, buffalos, sheep, goats and camels, all of which are still used in various parts of the world for the production of milk for human use (Fig. 1.1 & 1.2).

Milk is the secretion of the mammary glands of animals. For human consumption, milk is that liquid obtained from the cow or the buffalo during the period following at least 72 hours after calving or until the milk is colostrums-free. It is a complex biological fluid consisting of seven main components: water, fat, protein, sugar (lactose), minerals, vitamins and enzymes. Milk is a white opaque fluid in which fat is present as an emulsion, protein and some mineral matters in colloidal suspension and lactose together with some minerals and soluble proteins in true solution. The opacity of milk is due to its content of suspended particles of fat, proteins and certain minerals. The colour varies from white to yellow depending on the carotene content of the fat. Skimmed milk is more transparent with a slightly bluish tinge. Milk of a good flavour has a pleasant, slightly sweet taste, and no odour. It is an excellent source of calcium, phosphorous and riboflavin. Vitamin A and D are currently added to whole milk, partly skimmed and skimmed milk.

Milk production in India is a subsidiary activity of agriculture in contrast to the organized dairy sector in the western countries. Farmers and landless labour maintain one to five milch animals. As a result, small quantities of milk are produced in a scattered manner. Due to this reason, milk procurement models from western countries, such as bulk cooling and bulk transportation are not applicable under Indian conditions. Collection of small amounts of milk is scattered over long distances and, therefore, poses a formidable challenge in maintaining the quality attributes and keeping costs down.

3.1. Rural Milk Collection

A systematic approach to rural milk collection suitable for the tropical climate and techno-economic conditions prevailing in India has been developed, based on the indigenous experience gained over the past few decades. In the first phase, extensive surveys are undertaken in the milkshed areas, where the milk plant is to be established. The second phase involves ‘route planning’ taking into account, availability of quantities of milk, access to roads for plying vehicles and distance from the site of dairy plant. Then zones are identified, representing equal costs of collection and transportation. In the third phase, planning is done for locating the primary collection centres as well as chilling centres, where, milk can be cooled to 4ºC before transporting to the milk plant. Milk may be collected from individual producers either by the contractor or by forming village level cooperative societies.

Milk, on reception at the dairy factory is subjected to various unit operations on its way to product manufacture. Processing is applied as a means to convert liquid milk into products or to render the milk (and products) safe from harmful organisms. The basic processing operations to which milk is subjected at processing units have been described in this chapter. The common processing operations employed are depicted in Fig. 4.1. Several of these operations are routine compulsory processes common to all dairies, while certain others are undertaken for specialized purposes in some dairies.

4.1. Filtration and Clarification

At the time of milking various foreign materials such as dirt, feed, manure, dandruff, hair, flies, dust particles, worn out cells, cell debris and many other undesirable substances may find their way into milk. The process of removal of this extraneous matter (solid particles of higher density than that of milk) is called filtration or clarification. This can be achieved either by simple filtration through specially woven filter cloth or continuous process of centrifugal clarification that helps

Milk, as secreted in the udder of a healthy animal is practically sterile, but during its transit to the processing plant, becomes heavily contaminated with a variety of micro-organisms. These may be responsible for spoilage of milk or for causing diseases in animals and human beings. It thus becomes imperative that adequate heat treatment is given to milk to destroy these micro-organisms, thus increasing the shelf-life of milk as well as making it safe. Varied heat treatments offer the potential of producing different kinds of processed milk to satisfy the needs of the consumer. To cater to the ever-increasing demand of consumers, several varieties of processed milk are available in the market, some of which are discussed below.

5.1. Pasteurised Milk

Pasteurisation was named after the renowned French scientist Louis Pasteur, who discovered that spoilage organisms could be inactivated in wine by applying heat at temperatures below its boiling point. The process was later applied to milk and remains the most important operation in the processing of milk.

It is the process by which every particle of milk is heated to such temperature-time combinations (usually to 63°C for not less than 30 minutes or to 72°C for not less than 15 seconds) and promptly cooled to 4°C or below so as to destroy any harmful bacteria that may be present without affecting flavour and food value. Pasteurisation does not involve the use of any additives. Apart from making milk safe to drink, pasteurisation increases the length of time it can be kept before it spoils. The nutrient losses due to pasteurisation are so small, that they are considered insignificant.

Packaging is a tool that is used to contain the product, protect the product from environmental hazards and help in marketing the product. Examples of ideal natural packaging systems are that of a banana, orange, coconut and egg, where the packaging is provided by nature. The major step forward in the food processing arena has been the ability to protect and preserve products with packaging and hence ensuring the availability of fresh and processed products out of season and over long distances in various forms. Milk is a highly perishable product and is not uniformly available round the year to the whole country due to geographical and genetic variations. If dairy products are to be available all the year round the country, irrespective of the season and area, it must be presented in packages that are convenient to purchase and use.

Packaging has additional responsibilities of providing convenience, safety and facilitating, besides handling, storage and distribution of products. It should prevent spoilage of food by microbial or insect attack. It also preserves the quality and nutritive value of many foods by the exclusion of oxygen and the control of moisture loss or gain. It increases the shelf-life and ensures longer availability and contributes to the product image through structural and graphic design. Product information is also given out through the medium of labeling, which acts as a tool for marketing and advertising.

Cleaning and sanitisation are the two processes employed in dairy industry to ensure hygiene and product safety. The safety of milk and milk products is a very important aspect and every attempt should be made, during processing, to minimize contamination through handling and processing equipments. The accumulated dried milk solids (milk stones) consist largely of calcium phosphate, milk proteins (precipitated, coagulated and baked on by heat) and insoluble calcium salts from water and washing detergents. The surface can also contain biofilms, which are formed by the incorporation of bacteria into the accumulated inorganic and organic materials that attach to most surfaces. With time and in the presence of nutrients, a biofilm and the bacteria within the biofilm will grow and become strongly attached to the surface. The removal of dairy soil, milk stones as well biofilms is the prime objective of the cleaning process. International Dairy Federation (IDF) defines a clean surface as one which is free from residual film or soil that will not contaminate the food products coming in contact with it.

While cleaning refers to the removal of soil from the surface of the equipment, sanitisation implies destruction of all pathogenic and almost all non-pathogenic organisms. Cleaning and sanitisation are complimentary processes. Either of the processes alone will not achieve the desired result, which is to leave the surface as free as possible from soil and viable organisms. In actual practice cleaning and sanitisation overlap to some extent, as during cleaning a high proportion of bacteria are destroyed and others get removed in the detergent solution. Inadequate or faulty cleaning and sanitisation can have serious consequences, as milk is a prefect nutrient in which bacteria can multiply. A thorough understanding of the cleaning methods is, therefore, necessary for economic production of high quality food products.

India has achieved a commendable position of being the highest milk producing country in the world. Nearly 110 million tons of milk per annum is contributed by small and marginal farmers having 2-3 milch animals which are scattered in lakhs of villages across the length and breath of India. The poor socio-economic conditions are serious constraints in producing raw milk of good quality. The quality of milk is further deteriorated during subsequent handling and transportation. Milk being a product of biological origin, is extremely vulnerable to attack by microbes. It is also a good vehicle for additives and adulterants without any apparent changes in its appearance. Thus, milk is susceptible to several post-secretion changes, some natural and some man-made.

Indian dairy industry faces a mammoth task to meet the world quality standards, particularly in the present context of globalization and increasing quality conscious consumers. In view of the highly perishable nature of milk soon after it is secreted, it is important to monitor its quality by having a firmly installed quality assurance programme along the entire production-to-supply chain. This can be possible with application of sensitive, accurate and rapid methodologies as a tool in quality assurance programmes.

Quality comprises of several attributes ranging from physical, chemical, technological and bacteriological through nutritional to aesthetic. All dairy plants have a quality assurance laboratory (Fig. 8.1) and usually follow chemical quality control with the intention of payments to contractors/producers, processing of milk and meeting mandatory requirements for end products. Quality is judged both by objective and subjective tests.

The dairy processing industry in India deals mainly with the fluid milk and/or short shelf life products, despite India being the largest producer of milk in the world, with an output bordering the 110 million ton mark. This feature offers immense potential in the area of R&D in dairy processing in terms of value addition. The potential gains are many, including higher returns for producers and advantages in terms of health, therapeutic, nutritional and/or gastronomy for the consumers. However, the Indian Dairy Industry can amass possible benefits by being a global contender in trade only when its products are at par with those available in the rest of the world in terms of price and quality. It is evident from the post-WTO scenario that for sustainability, Indian dairy industry will need to maintain wholehearted commitment to quality management right from the farm to the consumer, shedding its inhibitions and resistance to changes.

9.1. WTO Agreements and Food Industry

The General Agreement on Tariffs and Trade (GATT) was formed in 1947 and lasted until 1994, when it was replaced by the World Trade Organization (WTO) in 1995. The WTO is the only global international organization dealing with the rules of trade between nations. It provides a forum for negotiating agreements aimed at reducing obstacles to international trade and ensuring fair deal for all, thus contributing to economic growth and development. Currently, there are 16 agreements to which all WTO members are parties and two agreements to which only some WTO members are parties. WTO currently has 153 members, of which 117 are developing countries or separate customs territories. The Head Quarters of WTO is at Geneva (Switzerland) and the official languages are English, French and Spanish.

Plant body consists of numerous microscopic box like components called cells. The word cell has been derived from the Latin word cellula, meaning a small room. The descriptive term for this smallest living biological structure was coined by Robert Hooke in a book he published in 1665. When he compared the cork cells, he saw through his microscope to the small rooms monks lived in. The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life, which is classified as a living thing and is often called the building block of life (Maton et al., 1997). It is defined as a mass of protoplasm surrounded by a membrane- the plasma membrane- within which complicated chemical reactions are going on.

The capacity to reproduce is one of the most important characteristics of all living beings. Reproduction is a process of producing offspring and is aimed to preserve individual species. This is known for self-perpetuation. There are several modes of reproduction, which vary from species to species, in available conditions. All the reproductive methods of plants are broadly classified into two types, i.e., (i) asexual reproduction (apomixis) and (ii) sexual reproduction (amphimixis). In asexual reproduction, the new individuals are produced by any means other than the fusion of sex gametes. In sexual reproduction, the gametes from male (androecium) and female organs (gynoecium) of the flower are fused to produce a zygote (Schranz et al., 2005; Rodrigues et al., 2008). Amphmixis and apomixis are the two sides of same coin (Curtis and Grossniklaus, 2007).

Photosynthesis- the word photo refers to light and synthesis means preparation. Thus, photosynthesis is the process by which the green plants use light energy of the sun to synthesize carbohydrates. Carbohydrates like simple sugars (glucose) can be stored as starch.

The green plants are eaten by the herbivores, which in turn are consumed by carnivores. Ultimately, the decomposers derive their nutrition from the dead plants and animals. Thus, all organisms are dependent directly or indirectly on green plants, which synthesize food by photosynthesis. Thus, photosynthesis is the most important life sustaining process of nature (Calvin, 1976; Emerson and Arnold, 1932). Photosynthesis is a series of biochemical reactions, which can be essentially summarized as follows:

Respiration is the oxidative breakdown of complex substrate molecules such as starch, sugars, and organic acids normally present in plant cells to simpler molecules such as carbon dioxide and water. Concomitant with this catabolic reaction is the production of energy and intermediate molecules that are required to sustain the myriad of metabolic reactions essential for the maintenance of cellular organization and membrane integrity of living cells. Since respiration rate is so tightly coupled to the rate of metabolism, the measurements of respiration provide an easy non-destructive means of monitoring the metabolic and physiological state of tissues, e.g., the events of senescence and ripening are often signaled by abrupt changes in respiration.

Maintaining a supply of high-energy compounds like adenosine triphosphate (ATP), nicotinamide adenine dinucleotide (NADH) and pyrophosphate (PPi) is a primary function of respiration. Nicotinamide adenine dinucleotide plays very important role in mitochondrial matrix (Moller and Ramusson, 1998). The overall process of aerobic respiration involves regeneration of ATP from adenosine diphosphate (ADP) and inorganic phosphate (P_i) with the release of carbon dioxide and water. If glucose is used diphosphatas substrate, the overall equation for respiration can be written as follows:

The transition from vegetative to floral meristems in higher plants is programmed by the coincidence of internal and environmental signals. The timing of floral transition has a direct impact on reproductive success. One of the most important environmental factors that affect the transition is the change in day length (photoperiod). Classical experiments imply that plants monitor photoperiods in the leaf and transmit that information coded within an elusive signal dubbed florigen to the apex to reprogram development. Recent advances in Arabidopsis research indicate that the core of the day-length measurement mechanism lies in the circadian regulation of CONSTANS (CO) expression and the subsequent photoperiodic induction of the expression of FLOWERING LOCUS T (FT) gene, which might encode a major component of florigen. The florigen paradigm was conceived in photoperiod-sensitive plants; nevertheless, it implies that although it is activated by different stimuli in different flowering systems but the signal is common to all plants. Flowering time, the major regulatory transition of plant sequential development, is modulated by multiple endogenous and environmental factors.

Flowers are the reproductive structures of Angiosperms. The apical shoot meristem of the vegetative plant continues to produce new leaves and vegetative buds, which may develop into branches, but after sometime, the meristem, instead of producing leaves and branches, becomes transformed into specialized reproductive structures called flowers. The transformation of vegetative shoot apex into re-productive structure is called flowering. The process of flowering is controlled by two main important environmental factors, i.e., (i) the duration of light received by the plant called photoperiod and (ii) the low temperature treatment given to the seed or the plant referred to as vernalization (Figure 6.1).

Fruits provide a suitable environment for seed maturation and often a mechanism for the dispersal of mature seeds. By anatomical definition, fruit is a mature ovary, and therefore, includes carpel tissues in part or in whole. However, many fleshy fruit species develop mature fruit tissues by including extra-carpellary floral components. The examples include strawberry, pineapple, mulberry and pome fruit (apple, pear, etc.) in which the receptacle, bracts, calyx and floral tube (the fused base of floral organs), respectively constitute majority of mature fruit tissues. Even species with fruit derived from carpel tissue exclusively can display a range of developmental programs, spanning the relatively uniform single expanded carpel or drupe of stone fruit to the differentiated carpel tissues, giving rise to the peel (flavedo) and multi-carpel flesh as observed in citrus and banana. Although genetic selection of agriculturally valuable fruits is being done since centuries but most of the information about how fruits develop, how this development is coordinated with embryonic development and seed formation and the molecular, cellular and physiological events that control fruit growth and differentiation are still lacking. In the following sections, the various aspects controlling fruit setting and development have been discussed.

In addition to pathogenic diseases, numerous abiotic disorders may also arise during growth, development and post-harvest storage of solanaceous vegetables. The physiological disorders of vegetables that have been included in this chapter are directly or indirectly associated with genetic, cultural, nutritional, physiological and environmental factors, and in most of the cases, the definite cause of disorder is not well understood due to the association of numerous factors together. These disorders may be related to colour, shape and form/condition of the produce. The genesis of physiological maladies was earlier poorly understand due to complexity in their characteristic symptoms but at present is relatively more transparent. The characteristic symptoms of abiotic disorders discussed below have not been attributed solely to a single agent or to a single cultural or environmental factor. The environmental factors correlated with the incidence of these disorders include high light intensities and low or high temperature of that growing area. For many abiotic disorders, very limited research work has been done, and the causes are poorly understood both in terms of why cultivars differ in susceptibility and why certain environmental factors predispose the plants or parts of the plant to the disorder. The growers feel concerned with the incidence of abiotic disorders as these cause huge economic loss. Therefore, the control of these abiotic disorders is essential for profitable production of solanaceous vegetable crops. In this chapter, emphasis has been given on practical aspects of diagnosis and potential control measures.

Fresh fruits are an important component of our diet since they provide essential nutrients like minerals and vitamins and are often attractive to the consumer because of their taste, texture, colour, aroma and flavour. Fruits of different species are botanically different, and they may be derived from various parts of the flower, including the pericarp, mesocarp and receptacle. Growth of fruit tissues is initiated shortly after fertilization and accompanied by the accumulation of food reserves donated by the parent plant. Fruit ripening corresponds to a number of physiological, structural and biochemical changes, which make the fruit attractive to the consumers. These changes include physical changes, viz. the changes in colour, texture, taste, aroma and flavour, and the metabolic changes such as changes in the level of enzymes and gene expression. The varieties of mechanism, which exist in different fruits to bring about a series of these changes to make them attractive for consumption, have been summarized in Table 9.1.

Because of the variety of ways in which these quality attributes are generated, there are significant differences existing in enzymes involved in ripening of different types of fruit. Once initiated, these physiological and biochemical modifications continue until the fruit is in peak condition for consumption. If the fruits are not harvested at appropriate stage of maturity, these changes continue and make them more susceptible to mechanical damage, infection and senescence. Since harvesting fruits at right stage of their maturity is critical, it is important to understand the biochemistry of fruit ripening process fully. This chapter will highlight the biochemical and metabolic changes involved during fruit ripening to make the fruit acceptable for potential consumers. Some of the possible genetic manipulations, which can be done to delay the onset of these ripening related changes, are given in later part of the chapter.

Most of the plants undergo a period of rest, and in this period, the growth activities temporarily halt. The whole plant looses its aerial parts and undergoes a rest period in the form of rhizome, corm, or tuber. Researchers who study fruit trees use the term rest for dormancy (Samish, 1954). This period is sometimes called as quiescence. The term rest and quiescence can be included under common category dormancy. Some workers differentiate the term dormancy and rest period (Burton, 1964). Wareing and Co-workers (Robinson and Wareing, 1964; Wareing et al., 1964) isolated dormancy inducing substance in sycamore seedlings (Acer pseudoplatanus) which was named as dormin. Further, analysis of this substance by Cornforth et al. (1965) reveals that dormin was identical to Abscisin-II (a substance speeding the abscission of the young flowers of Lupinus luteus and have antiauxin effect).

Dormancy can be defined as an arrest in development of buds, seeds, embryos, or spores under conditions otherwise suited for growth (Taylorson and Hendricks, 1977). It is a survival strategy (exhibited by many plant species), which enables them to survive in climates where part of the year such as winter or dry seasons is unsuitable for growth. The dormancy may be due to the factors within the dormant organ or seed itself and it is called spontaneous dormancy. This type of dormancy is found in seeds, buds and perenating organs like tubers, bulbs, bulbils, corms and rhizomes. In some weeds, dormancy is caused by high or low temperature and this type of dormancy is called as imposed dormancy. Seeds normally germinate in darkness but are inhibited by light are considered to become dormant after exposure to light (Bewley and Black, 1982; 1985). Seeds that require light for germination are said to be photo dormant.

Plant hormone is an organic compound synthesized in one part of the plant body and translocated to another part where in very low concentration it causes a physiological response. However, this definition could not demarcate the vitamins and other growth influencing substances from hormones. For this reason, the term Phytohormone was introduced with included vitamins, growth hormones and flowering hormones. Phytohormone can be defined as an organic substance produced naturally in higher plants, controlling growth or other physiological functions at a site remote from its place of synthesis and active in minute amounts, whereas, an organic substance, which promotes growth, i.e., irreversible increase in height or volume, when applied in low concentration to the shoots of plant is known as growth hormone.

The plant hormones are naturally occurring as they are synthesized by the plant. On the other hand, there are several manufactured chemicals, which often resemble the hormones in physiological action and molecular structures, are called growth regulators. Generally, there are five classes of phytohormones.

The phytohormones universally present in all plants are classified as under:

Water is the most abundant compound on the earth but its sufficient availability is always a big constraint in crop production, particularly in arid and semi-arid areas since agriculture is the last priority for good quality water due to severe competition with public health and industrial demand, hence, the judicious and efficient use of water for irrigation in agriculture needs through knowledge of soil-plant-water relationship. The integrated approach for water management in rain fed areas or irrigated agriculture in soil-plant-atmosphere system helps in the selection of suitable crops and varieties and also helps in improving the crop yield and water use efficiency in relation to water supplying capacity of soil profile depending on its texture and rhizosphere depth. Similarly, atmospheric demand of evapotranspiration by various weather parameters via temperature, relative humidity, radiation, rainfall and wind speed is highly variable during the crop season depending on geographical location and is highly area specific. In irrigated area, the saving of irrigation water through improved management practices will further help in extending the irrigated areas with same amount of water, which will further boost agricultural production and sustainability.

Most of the earth’s total water is contained in oceans (96%), a small portion (2%) as snow and ice and the rest (2%) in the water bodies of the continents. Oceans, lakes, rivers and other water bodies of the earth are called hydrosphere. Continuous circulation of water between hydrosphere, atmosphere and lithosphere is known as hydrological cycle (Figure 12.1). Schematic diagram illustrating the earth’s water cycle– the hydrological cycle.

Measurement of soil moisture content is one of the most routinely done soil characterization. Knowledge of soil moisture is essential to understand the behaviour of soil as a medium for plant growth. Moreover, this property of soil helps to explain other processes of the soil. There are several methods of measuring soil moisture content. The most commonly used methods are gravimetric and tensiometric. The standard gravimetric method is quite accurate and simple but is time consuming, cumbersome and destructive. Furthermore, due to relatively small soil samples that are taken, the variability between replicates is great.

Gravimetric Method

Equipment needed includes zip-loc bags or aluminium moisture boxes and soil sampling tools. Soil sampling tools can be a soil probe, auger, or even a post-hole digger. Balance and scale should have accuracy to 0.1 gram. Proper sampling of the field is important to obtain a representative sample of the field. The soil sample should be collected from the field at a minimum of three locations, and the sample locations chosen should represent the entire field. Sampling from the small areas of low spots or ridges that do not represent majority of the field should be avoided. If there are major changes in soil classification within a field, the field should be divided into sub-sites and samples are collected accordingly.

Drought is one of the most frequent and widely spread stress factors that limit the production of vegetables in the world. Nearly every piece of cultivated land including those in the irrigated areas could be subjected to drought. However, the frequency, duration, severity, timing and extent of drought vary greatly from region to region.

The stress caused by deficit water in the living plant system, which is capable of inducing a potential injury, is called drought stress. Drought can also be defined as scarcity of water for plants and can be due to soil, atmospheric and physiological factors. In our conditions, the great damage to the production of vegetables is brought about by soil drought, which occurs when rapidly available water is spent from zone of the active rhizosphere. That particular moment represents the beginning of drought and as the water reserves in the soil become closer to the lower limit of optimum moisture, the drought becomes more intensive. Under such conditions, plants survive on the limited water available in the active rhizosphere and deeper soil layers, and this water is used to maintain essential life processes at the expense of crop yield.

The lack of precipitation causes drought; the area of cultivable soil in our country under irrigation is very small and so is the possibility to diminish the negative consequences of occasional shortage of precipitation. Aiming to reduce damage caused by drought, a huge number of research-experiments on drought, especially on tolerance has been conducted worldwide. Here, the attempts have been made to review the work done on drought tolerance by national and international centers.