Effect Of Drying And Pre Drying Treatment Of Fruit And Vegetable Using Tomatoes

Description

ABSTRACT

Fruits and vegetables are dried to enhance storage stability, minimize packaging requirement and reduce transport weight. Preservation of fruits and vegetables through drying based on sun and solar drying techniques which cause poor quality and product contamination. Energy consumption and quality of dried products are critical parameters in the selection of drying process. An optimum drying system for the preparation of quality dehydrated products is cost effective as it shortens the drying time and cause minimum damage to the product. To reduce the energy utilization and operational cost new dimensions came up in drying techniques. At the end of this work, the drying method of tomatoes wasa conducted and a result was drafted.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE STUDY
• AIM OF THE STUDY
• OBJECTIVE OF THE STUDY
• SIGNIFICANCE OF THE STUDY

CHAPTER TWO

2.1       LITERATURE REVIEW

2.2      OVERVIEW OF THE STUDY

2.3     DIFFERENT METHOD OF DRYING PRE-DRYING TREATMENT OF FRUITS AND VEGETABLE

2.4    QUALITY ATTRIBUTES AND CLASSIFICATION

2.5     ENERGY EFFICIENCY IN DRYING

2.6     REVIEW OF RELATED STUDY

 

CHAPTER THREE

3.1      METHODOLOGY

               3.2     MATERIALS AND METHODS

CHAPTER FOUR

4.1     RESULTS AND DISCUSSION

4.2     EFFECT OF DRYING METHOD AND PRE-TREATMENT ON SOME

CHAPTER FIVE

5.1     CONCLUSIONS

5.2     REFERENCES

CHAPTER ONE

1.0                                                     INTRODUCTION

Tomato (Lycopersicon esculentun Mill) is botanically classified as a  fruit and  a member of the Solanaceae family. Tomato is a popular and versatile fruit that comes in over a thousand different varieties that vary in shape, size and colour. Tomatoes have fleshy internal segments filled with slippery seeds surrounded by a watery matrix; they can be red, yellow, orange, green, purple or brown in colour (Smith,  1994).  Tomatoes are popular for their culinary properties and health benefits. They are a natural source of lycopene, a carotenoid that reduces the risk of cancer and coronary heart  disease (Rao and Agarwal, 1999, Etminan, et al., 2004). Tomato, aside from being tasty, promotes healthy nutritional balance being a good source of vitamins A and C. Tomato  may be  eaten fresh as salad or processed into pastes, powder or purees, which are for cooking in stew or soup and producing fruit drinks. Tomato has a limited shelf life at ambient condition and it is highly perishable. It create glut during production season and becomes scarce during off season (Smith, 1994,  FAO, 2006).  One of the most important methods  of reducing tomato losses is by drying which is a common form of food preservation. Drying agricultural products is aimed at reducing the moisture content of product to  a level that allows the food to be stored safely for an extended period. In addition to increasing the shelf-life, drying reduces the weight and volume of the product, thereby reducing packing, storage and transportation costs. Dried tomato products are used for making pizza and various culinary dishes. During the drying process, the moisture content of the dried tomato product is typically reduced to less than or equal to 15% (Zanoni et al., 1999).

Tomato as other fruits and vegetable can be dried using various methods such as sun drying, spray drying, oven drying etc. The quality of dehydrated  tomato  depends  on many parameters such as tomato variety, total soluble solid content of  the  fresh product, air humidity, size of the tomato segments, air temperature and velocity as well as the efficiency of the drying system and its drying power rate (Dewanto et al., 2002, Chen, et  al, 2000, Olorun, 1990). Tomato powder is produced by drying fresh tomatoes. In advanced countries, tomato powder is made by turning fresh tomatoes into a slurry and spray drying. With spray drying, hot gas is forced through a liquid  mixture,  creating  a fine powder which is used as a base for tomato paste. Tomato powder keeps longer than most tomato paste, and allows people to mix up exactly as much as they need for a fresh, dear flavour. It can also be used to make tomato soups, or to fortify broths and pasta.

The use of pre-treatment on crops before drying is aimed at preventing fruits from darkening, many light-colour fruits, such as apples, darken rapidly when cut and  exposed to air. If not pre-treated, these fruits will continue to darken after being dried (Lewicki et al., 2002, Hartz, 2008). The commonly used pre-treatment methods  as reported by Lewicki et al., 2002 are sulfuring, sulfite dip and syrup blanching. The work focuses on the evaluation the effect of sun and oven drying methods and pre-treatments on some physico-chemical quality attributes of tomato powder.

• BACKGROUND OF THE STUDY

Fruits and vegetables are important sources of essential dietary nutrients such as vitamins, minerals and fibre. Since the moisture content of fresh fruits and vegetables is more than 80%, they are classified as highly perishable commodities (Or satetal. 2006). Keeping the product fresh is the best way to maintain its nutritional value, but most storage techniques require low temperatures, which are difficult to maintain throughout the distribution chain. On the other hand, drying is a suitable alternative for post harvest management especially in countries like India where exist poorly established low temperature distribution and handling facilities. It is noted that over 20% of the world perishable crops are dried to increase shelf-life and promote food security (Grabowski et al. 2003). Fruits, vegetables and their products are dried to enhance storage stability, minimise packaging requirements and reduce transport weight. Nonetheless, in India hardly any portion of perishables are dried which leads to enormous loss in terms of money and labour besides steep rise in prices of commodities during the off season.

The preservation of fruits and vegetables through dry-ing dates back many centuries and is based on sun and solar drying techniques. The poor quality and product contamination lead to the development of alternate drying technologies (Bezyma and Kutovoy 2005). The most appli-cable method of drying includes freeze, vacuum, osmotic, cabinet or tray, fluidized bed, spouted bed, Ohmic, micro wave and combination thereof (George etal. 2004). Except for freeze drying, applying heat during drying through conduction, convection and radiation are the basic techniques used to force water to vapourise, while forced air is applied to encourage the removal of vapour. A large number of food and bio-materials are dehydrated in a variety of units with diverse processing conditions. The choice of drying method depends on various factors such as the type of product, availability of dryer, cost of dehydration and final quality of desiccated product. Energy consumption and quality of dried products are other critical parameters in the selection of a drying process. To reduce the use of fossil fuel, electrical energy is an alternate source of energy for drying applications especially where electricity is generated by a renewable energy source such as hydro power or wind power (Raghavan and Orsat 1998, Raghavan et al. 2005).

Keeping these in view, the present study is focusing on recent developments in drying and pre-drying of fruit and vegetable.

1.2                                                  AIM OF THE STUDY

The aim of this work is to protect fruits or crops from darkening, many light-coloured fruits such as apples, darken rapidly when cut and  exposed to air, using drying and pre drying.

1.3                                               OBJECTIVE OF THE STUDY

The main objectives of this work are to evaluate the effect of drying methods and pre-treatments on some physico-chemical quality attributes of tomato.

1.4                                        SIGNIFICANCE OF THE STUDY

Fruits and vegetables are dried to enhance storage stability, minimize packaging requirement and reduce transport weight. Preservation of fruits and vegetables through drying techniques which cause poor quality and product contamination. Energy consumption and quality of dried products are critical parameters in the selection of drying process. An optimum drying system for the preparation of quality dehydrated products is cost effective as it shortens the drying time and cause minimum damage to the product.

Fruits, vegetables and their products in the dried form are good sources of energy, minerals and vitamins. However, during the process of dehydration, there are changes in nutritional quality.

Dried food products are considered safe with respect to microbial hazard. There is a critical water activity (aw) below which no micro organisms can grow.

PROBLEM OF THE STUDY

1. Browning, lipid oxidation, color loss and change of flavor in foods can occur during drying and storage.
2. Physical changes, such as structure, case hardening, collapse, pore formation, cracking, re-hydration, caking and stickiness can influence the quality of final dried products. Hot air drying usually destroys the cell structure and thereby takes more time for dehydration while due to solid state of water during freeze drying protects primary structure and shape of products keeping the cells almost intact, with a high porosity end products.