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FST00128 - EFFECT OF PRE-TREATMENT AND DRYING METHODS ON SOME PROPERTIES OF DRIED TOMATO SLICES USING TWO VARIETIES


CHAPTER ONE

  • INTRODUCTION
    • Background of the Study

Tomato (Lycopersicumesculentum) is one of the world’s most commercially produced vegetable (Ensmingeret al., 1994) and is also one of the world’s major food crops (Fruscianteetal., 2000) tomato production in Nigeria has more than doubled in the last 10 years and the production in 2001 alone was 879,000 metric tonnes(FAO, 2002) which is largely consumed in its fresh state. The global tomato production output has risen from 107 to 130 tonnesbetween 2001 and 2007 (FAO.2008). Tomato is a fleshy berry regarded as a very popular perishable fruit (Okorieet al., 2004). It is an important herbaceous perennial vegetable grown for its edible fruit and it is an annual vegetable in the temperate region.

Tomato(Lycopersicon esculentum)which is one of the most important fresh vegetables in the southern part of Nigeria and  highly perishable because they deteriorate rapidly during handling and storage due to physiological breakdown as a result of natural ripening processes, water loss, temperature injury, physical damage or invasionby microorganismleading to huge losses. Tomatoes (Lycopersiconesculentum) play a vital role in a healthy diet. Tomatoes are extremely beneficial to human health for they are rich in folate, potassium, vitamin A and vitamin C, carotenoids, and flavonoids (Beecher,1997). Many of the carotenoids such as lycopene arotene flavonoids seem to protect men from various cardiovascular diseases and different types of cancer (Oshimaet al., 1996; Woldet al., 2004). Tomatoes are the primary source of lycopene in many people’s diets (slimestad&verheul, 2005). Lycopene is responsible for the red color present in the tomato (Heinz; Sabioetal., 2003.)

      However, tomato is highly perishable in the fresh state leading to wastage and losses during the peak harvesting period (Akanbiet al., 2006). It has the shortest shelf lifeamong fruits and vegetables due to its high metabolic reactions which lead to loss in weight, quality, food and economic values. The prevention of these losses and wastage is of major interest especially when there is subsequent imbalance in supply and demand at the harvesting off-season. The post-harvest section of the food system is a crisis zone of the food sector in developing countries like Nigeria. This could be attributed to negligence, poor processing technology, inefficient management, inadequate infrastructure, poor storage conditions, among others. Post harvest handling is then the ultimate stage in the process of producing quality tomatoes but being able to maintain these present many challenges such as the production costs, transportation cost.

Drying is the most common method of preservation; it involves drum drying, vacuum drying, sprayed drying and foam-mat drying which has been embarked upon as an effort to produce dried tomato slices. The sprays drying have been reported to be very useful where the desired characteristics in the dried tomato slices are required (Wallace et al., 1993). While the principle of spray drying quite simple, its technological realization is difficult. In addition, the technology involve are generally capital intensive and are not suitable for small scale farmers, particularly in Africa and the developing world. Hence oven drying an alternative to spray drying would be employed. The demand for dehydrated tomato is increasing rapidly both in domestic and in international markets with major portion of it being used for preparation of convenience foods (Davoodi, 2005).

Pretreatments are done to fruits and vegetative before drying, canning, freezing e.t.c blanching is a form of pretreatment in which fruits or vegetables are heated for the purpose of inactivating enzymes modifying texture, preserving colour, flavor and nutritional value and removing trapped air. Chemicals to be used in blanching are potassium metabisulfite and calcium chloride. Potassium metabisulfites a food preservative, which preserves the natural colour of food and protects food against bacteria when used for preserving vegetables and fruit, it preserves their freshness and their natural colour. Calcium chloride is a chemical compound of calcium and chlorine. It is calcium salt used in food preservation. It helps soften foods maintain their shape.

  • STATEMENT OF PROBLEM

                  Since tomatoes are highly perishable, there is a need to develop the best method in preserving them to reduce the rate at wish they are been wasted. There is need for the processing of tomato into dried slices for the elongation in its shelf life during storage.

  • JUSTIFICATION

                  One of the needs of processing tomato into dried slices is to limit the post-harvest losses and wastages of harvested tomatoes during storage and to preserve the natural components of tomatoes until is ready for use. The pretreatment that would be done on dried tomato is to increase the shelf life retaining the nutritional value, colour, modifying the texture, inactivating the enzymes and removing trapped air.

 

 

 

 

 

 

1.4             SCOPE OF STUDY

      Two varieties of tomato will be purchased from a neighboring market. Pretreatment will be done on the varieties using both calcium chloride and potassium metabisulphite using sun drying method and cabinet drying method.

 

1.5             AIM AND OBJECTIVES

  • AIM

      To determine the effect of pre-treatment and drying methods on some properties of dried tomato slices using two varieties.

1.5.2          OBJECTIVES

  • To determine the effect of drying methods on tomato slices.
  • To study effect of pretreatment on dried tomato slices.