eChapters

1. Introduction

Intermediate moisture foods are semi moist foods that have some of their water bound by glycerol, sorbitol, salt or certain organic acids, thus preventing the growth of many microorganisms (Stewart et al. 2001). It is now well recognized that fruits and vegetables are dehydrated to an intermediate moisture level (20-50%) (Stewart et al. 2001; Purvi et al. 2003). As the intermediate moisture products are characterized by a semi moist consistency so these foods have enough moisture content to permit easy chewing but low enough water content to prevent spoilage production of intermediate moisture foods is based on an increased scientific understanding of the chemical reactions involved in traditional food preservation methods (Purvi et al. 2003).
There will be better retention of original flavor and texture compared to fully dried products, with concomitant reduction in bulk, weight and cost of packaging, transportation and storage. Such intermediate moisture foods are more appropriate for developing countries in view of their minimal processing requirements, stability under ambient conditions, safety, convenience, ease of nutrient content adjustment, energy savings and low capital investment. They are also eminently more suited than dehydrated or canned foods for military rations (FAO, 2005).

1. Introduction

Pulpy and juicy fruits like orange, guava, banana, grape, mango, papaya, pears, apples and jackfruit can be converted into fruit products like squashes, juices, cordials and ready-to-serve (RTS) fruit beverages. These RTS fruit beverages are both refreshing and thirst quenching and have become very popular. Liquid fruits are the clarified juices prepared from these pulpy and juicy fruits. There is a demand for liquid fruits in the international market for various applications. The liquid fruits can be used as a natural alternative to synthetic beverages. They can be suitably concentrated or diluted, blended with other juices and also can be carbonated as fruit based soft drinks. Removals of pulpy material from the juices make them easier to preserve by pasteurization and are amenable to carbonation. Pulpy fruits can be successfully processed into liquid fruits (clarified juices) by using pectic enzymes. The emphasis of the fruit juice processing industry has, so far, been mainly on conventional clarification processes like enzymatic and chemical treatments followed by filtration using filter aids; and concentration by vacuum evaporation.

1. Introduction

In this era of genomics, proteomics and metabolomics the challenge in nutritional science is to clarify human nutrient requirements and design nutritional strategies to promote health and functional longevity. Our ancient Indian belief that ‘we are what we ate’ and our future health as individuals may well depend upon what we eat today. Plant-based dietary antioxidants are believed to have an important role in the maintenance of human health because our endogenous antioxidants provide insufficient protection against the constant and unavoidable challenge of reactive oxygen species (ROS). We have various endogenous defense chemicals but they are inadequate to prevent oxidative damage that makes human system prone to various degenerative diseases. Hence, it is necessary for increased intake of dietary nutraceuticals that may help maintain the balance between oxidants and antioxidants, slow age-related changes, and prevent onset of degenerative diseases.

1. Introduction

At present there is an increasing demand for colourants from natural sources. Since there is a possibility of banning of synthetic colours in view of their carcinogenic properties and already a reduction in number of permitted synthetic colours from 13 to 8 numbers in our legislation (PFA, 2005), the demand for natural colours is evident. In Japan and European countries because of the green movement, the demand for synthetic colours has been reduced. Synthetic colours in global market account for 400 million dollars. Despite processing limitations and higher costs, the global market for natural colours is estimated to be more than 939 million dollars (Espszezola, 1998). Color is recognized as a major factor affecting food acceptance. The consumer expects a specific food to possess a well defined colour and rejects any appreciable deviation from the normal. The change in colour during the preparation of food is a useful guide to quality control and is used by many food processors as the criterion for selecting raw materials. The characteristic colour of raw food is due to the natural pigments present in the plant and animal material. These can be enhanced in processed food products through the addition of food colourants. Addition of colour can make up for the colour losses during processing. Some of the major groups of colours are anthocyanins, carotenoids, betalains, chlorophylls, flavones and chalcones. Some of the plant sources of pigments are kokum, roscelle, chilli, marigold, beetroot, grapes and safflower. Sources of natural colours can be plants, animals or microbes. Fruits and vegetables form one of the main plant sources of pigments. Some of the plant materials rich in colours viz., alfalfa, marigold, safflower, strawberry, aronia fruits, grapes, red cherries have been exploited for pigment extraction and the results have shown positive effects. Some of the interesting features of the work carried out by researchers in this area are presented in the following sections.

1. Introduction

Pectin is a polysaccharide present in the middle lamella of plant cell walls. The firmness and structure of the plant tissue are attributed to the presence of pectin in the middle lamella. The insoluble form of pectin is called protopectin and the soluble form is called soluble pectin (Kertez, 1951). Protopectin is abundant in green fruits and contributes to hardness of cell, where as soluble pectin is responsible for viscous nature of juice and pulp. Conversion of protopectin to soluble pectin results in loosening of the bonds between the cells and softening of the fruit tissues. Protopectin is reported to be hydrolyzed to pectin by enzyme action during ripening. Protopectin on restricted hydrolysis yields pectin or pectinic acid. Braconnot (1825) discovered pectin as the gelatinous principle of fruits.

1. Introduction

Food is processed for its preservation, hygienization or value addition. To date, the food preservation technologies such as canning, dehydration, freezing, pasteurization and controlled atmosphere and modified atmosphere packaging have been the main processes employed to preserve foods, with the use of antimicrobials and microwaves also being employed more recently. In future, however, technologies such as exposure to ionizing radiation, high pressure processing, ohmic heating and pulsed electric field processing, could potentially be the new alternatives to the above food preservation technologies.

Irradiation of food involves the exposing of food, either in prepacked form or as such to controlled doses of ionizing radiation being generated either by electrically driven machines such as electron beam accelerators, x-rays or gamma rays produced by radioactive isotopes such as CS-137,CO-60, to achieve certain desirable objectives. The process of exposing a range of food stuffs to specific doses of ionizing radiation is being used to extend the shelf life of food stuffs, to improve their overall safety and quality by eliminating pathogenic bacteria, by reducing number of food spoilage organisms, to reduce the bacterial load on herbs and spices and thereby making them safe to incorporate into food stuffs, to inhibit sprouting in stored tuber and bulb crops such as potatoes, onions and garlic, to disinfest grains, grain products and tropical fruits to prevent damage to the commodity and to meet the quarantine regulations(Arun Sharma, 2004, Farkas, 2006).

1. Introduction

Vegetables and fruits are the next in demand for human consumption after rice and wheat, in all parts of the globe. Fresh fruits & vegetables and their value added products are increasing in popularity day by day almost in all the countries, because of their richness in dietary fibre, minerals & vitamin contents and for their medicinal properties. Maintaining agricultural produce quality and its evaluation are thus naturally important. Decisions concerning maturity and ripeness of fruits and vegetables are based mostly on visual inspections, which are subjective in nature. The quality of fruits and vegetables is mostly decided on the basis of size, shape, colour, gloss, flavour, firmness, texture, taste and freedom from external as well as internal defects. Internal quality factors such as maturity, sugar content, acidity, oil content and internal defects, however, are difficult to evaluate non-destructively. Methods are needed to better predict the internal quality of fruits and vegetables without their destruction. Recently, there has been an increasing interest in non-destructive methods of quality evaluation, and a considerable amount of effort is being made in this direction. But the real problem is how these methods are to be exploited practically on commercial scales and what are the constraints faced in implementing them.

1. Introduction

Fruits and vegetables represent highly perishable items of agriculture, mainly because of their high water content in fresh form. Their production, yield and management under agriculture is dealt essentially under horticulture. They abound in species and varieties in different geographic regions of the world, influenced by the agro-climatic conditions. Some are endemic and confined to certain geographic regions only. Accordingly, they may be tropical, sub-tropical or temperate, depending on their requirements of temperature for growth and yield.

INTRODUCTION

Plants are susceptible to different types of pathogens, which are responsible for production of varied symptoms and causing losses. In the absence of the crops pathogens perpetuates in different manners and survival in the soil is one of the most important amongst these. Because of the constant presence of the pathogen in the soil, these become more destructive. These may reduce the plant growth, results in rotting of different plant parts, reduce yield or may cause the death of the plant. The destructiveness of soil borne pathogen increases because of the ability to survive in the soil as dormant structures for several years. Efficient control of soil borne diseases is thus difficult but can be achieved by employing various disease management practices in an integrated manner (Verma and Varma, 1992; Gupta, 1996, Gupta and Sharma, 1999).

INTRODUCTION

Rhizoctonia solani Kuhn (teleomorph: Thanatephorus cucumeris (Frank) Donk is cosmopolitan in soils. It is a destructive plant pathogen with an almost unlimited host range. The fungus inhabits in soils and causes damping-off of seedlings, root, crown and stem rots, and occasionally foliar blight (Baker, 1970). R. solani is an important symbiont with the saprophytic seedling stage (protocorm) of many orchids (Warcup, 1985). It aggressively colonizes organic matter and is one of the fastest growing fungi. According to available information, the isolates of R. solani possess the following-characteristics (Plate 2.1).

INTRODUCTION

Modern agriculture relies more on monoculture, which is highly energy intensive and has a narrow genetic base. This has disturbed the normal ecosystem and sometime results in disease epidemics. The problem becomes much more serious in case of soil borne pathogens, as soil medium is a highly complex living system and is also the habitat of many micro organisms including the pathogens whose activities are influenced by interaction in it. Many serious plant diseases are associated with soil-borne plant pathogens, which cause root rot, crown rot, damping off, blights, fruit decay and wilts in field and horticultural crops. Soil borne plant pathogens, which are most tricky and challenging ones, cause sustainable economic loss. Many important fungal pathogens reside in the soil and infect roots of crops often causing significant yield losses. Soil-borne diseases result from a reduction in biodiversity of soil organisms.

INTRODUCTION

Many economically important diseases are caused by Phytophthora spp. There are as many as 60 described Phytophthora species, most of which are primary invaders of plant tissues with limited saprophytic ability. Some important diseases with respect to symptoms, etiology and management have been described in this chapter as given below.

INTRODUCTION

Soil-borne pathogens cause heavy losses to most agricultural crops. Repeated planting of a crop in the same piece of land results in a high inoculum build-up, which forces the farmers either to change the crop or the land. Thus, the search for new, effective, inexpensive and non-hazardous methods for the control of soil-borne diseases is a continuous one. Over the years, efforts have been made to manage the soil-borne pathogens by employing fumigants, chemical pesticides, biological control agents, different type of soil amendments and also by causing modifications in different cultural practices. But, pathogen control is often hampered by the fact that both the inoculum of the pathogens and the lethal agents applied to the soil are affected by the soil’s physical, chemical and biological environment. Keeping in view the bottlenecks with different methods of management of soil-borne pathogens; harnessing of solar energy i.e. soil solarization is an effective method to control soil-borne pathogens.

INTRODUCTION

The genus Pratylenchus was established in 1936. It has a cosmopolitan distribution prevalent in temperate, sub-tropical and tropical regions. The species of Pratylenchus are popularly known as lesion nematode or meadow nematode. They are migratory endoparasites. Various pulse crops are damaged by them. P. thornei attacks chickpea,  P.zeae on mungbean (Walia and Seshadri, 1986); P. mulchandani on urdbean (Nanad Kumar et al., 1969) and Pratylenchus sp.on lentil (Mishra and Gaur, 1980) and cowpea (Aung and Prot, 1990).
Besides pulses species of Pratylenchus attack a number of other crops also. The infested plants exhibit various types of symptoms and results in heavy yield losses. Investigations have been made on various aspects of host-nematode relationship, distribution, host range, yield losses, biology, life cycle, disease cycle, interaction with other microorganism and management through cultural, physical, chemical, biological methods and host resistance.

INTRODUCTION

Fungi naturally present in soil and rhizosphere of various crops serve as potential biological control agents of various plant pathogens. Species of fungi occurring in the genus Trichoderma have gained significant importance for use as agents for control of several diseases of cultivated crops. The last decade has witnessed a tremendous break-through in the research efforts on biological control of plant diseases in India especially by using species of Trichoderma and Gliocladium. Several economically important plant diseases of a variety of crops were effectively managed by using Trichoderma based biofungicides.

The work on biocontrol of pigeonpea wilt by Bacillus subtilis by Dr. R S Vasudeva and his associates, published as a series of papers in Annals of Applied Biology during 1950 to 1965 can be considered as a starting point for Indian work on biological control of plant pathogens (Mukhopadhyay, 1994).

INTRODUCTION

In arid and semi-arid regions of India, besides weather aberrations, diseases caused by certain soil-borne pathogens are responsible for low productivity of agricultural crops. In addition to losses caused in annual crops, occurrence of these diseases in forestry takes away a major share. Because of the requirement for free water, diseases of aerial plant parts are much less common than those involving roots when plants are grown in dry regions where humidities are low and rains are infrequent and/or of short durations. Under these conditions, pathogens like Macrophomina phaseolina, Ganoderma lucidum, Cylindrocarpon lichenicola, Neocosmospora vasinfectum, Sclrotium rolfii and species of Fusarium (F. oxysporum, F. solani, F. equiseti, etc.) cause root rots and wilts in many commercially valuable and perennial plants.
Certain agro-climatic factors are attributed for the development of few specific diseases caused by soil-borne plant pathogens. Low organic matter, small microbial population coupled with poor moisture retention capacity of soil favour survival and multiplication of soil-borne pathogens (Fig. 12.1).

INTRODUCTION

Burgeoning human population and its elevated living standard have greatly demanded more agricultural production. But unfortunately agricultural crops suffer deadly due to many biotic and abiotic stresses. Of biotic stresses, phytonematodes, the hidden enemies of crops are real threat to successful and profitable cultivation of agricultural crops (Plate. 11.1). These, endoparasitic nematodes, Meloidogyne spp. and Heterodera spp., are mainly dreadful causing wrecking havoc to agricultural scenario. Chemical control of these, tiny parasites created residue, resistance, resurgence, hazardous and pollution problems to the growers as well as soil and atmospheric environment. To overcome these hazards, efforts are being made to go for non-chemicals means of nematodes management strategies in crops. Hence, a research work carried out on management of these endoparasitic nemas particularly Meloidogyne spp. and Heterodera spp., through non-chemical methods is reviewed in subsequent status.

INTRODUCTION

The fine feeder roots of many vascular plants are invaded by specific nonpathogenic fungi forming a distinct morphological unit known as mycorrhiza (In Greek, Mykes mean mushroom or fungus, rhiza mean root). Physiologically mycorrhiza represents a case of symbiosis.

The term mycorrhizae were coined by a German botanist Albert Bernard Frank in 1885 which literally mean “fungus-roots”.  Mycorrhizal fungi form a symbiotic association with agricultural and horticultural crops in addition to certain tropical tree species.
Mycorrhizal fungi are broadly classified in to two groups:
1) Ectomycorrhizae  
2) Endomycorrhizae.

INTRODUCTION

‘Wilting’ is a broad terminology used by Plant Protection Scientists.  Any disturbance or damage to the normal physiology of the plant leads to ‘wilting’ of plants.  Wilting in cotton is attributed to many factors and it is necessary to single out the actual cause for wilting before suggesting any remedial measure (Kannan, 1991).
Wilting in cotton could be due to any one or more factors as indicated below:

INTRODUCTION

In India, temperate fruits are grown successfully at locations above 3000 feet mean sea level in hilly areas of Himachal Pradesh, Jammu and Kashmir, Uttranchal, Sikkim, parts of North Eastern states like Assam, Arunachal Pradesh, Nagaland, Meghalaya etc. Mount Abu hills of Rajsthan and Nilgiris of Tamil Nadu also provide suitable agro-climatic conditions for growing some temperate fruits. Apart from apple; pear, peach, plum, apricot, cherry, almond and walnut are major temperate fruits being grown over 3.38 lakh hectares of area and play pivotal role in the economy of hilly farmers whose land is not otherwise considered suitable for traditional agriculture. They contribute about 11.5 percent of total area under fruits in the country, yet production is only 5 percent of the total. Incidence of many fungal, bacterial and viral diseases in these fruit crops is a major impediment in their successful cultivation and soil borne pathogens are of foremost importance and are responsible for premature death of the trees in the orchards. Amongst these, white root rot, collar rot, seedling blight, crown gall, hairy root are the major constraints which can cause as high as 40 percent damage in certain situations (Sharma and Sharma, 2001). Threat from the replant problem is causing concern due to its negative effect on the establishment of replanted sites due to soil sickness.