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EFFECT OF HEAT ON THE VITAMIN C CONTENT IN SOME SELECTED VARIETIES OF TOMATOES GROWN IN PANKSHIN/KANKE LGA OF PLATEAU STATE

 CHAPTER ONE

INTRODUCTION

1.1     Background to the Study

The center of origin of tomatoes has been debated by many. Some are suggesting the center to be the dry coastal desert of Peru (Jenkins, 1948, Preedy and Watson, 2008, Blanca et al., 2012) while others have suggested a dual center with one part in the coastal region between the Andes (Blanca et, al., 2012) and the ocean and the second part from South Mexico to Guatemala (Bauchet and Mathilde, 2012). Wild relatives of tomato are distributed in the Andes from Ecuador, through Peru and to Chile (Peralta et al., 2005), growing between sea level and 3300 meters above sea level (Blanca et, al., 2012) in diverse climate condition. The domestication is still unclear but linguistics evidence has postulated Peru and Mexico as the origins of domestication (Peralta et al., 2006). Tomatoes are known to be used in cooking in Mexico by the Aztecs already 500BC and were transferred to the rest of the world by the conquistadors after the capture of the Aztecs territotry (Bergiugnoux, 2014).

The cultivated tomato (Solanum lycopersicum) is the world’s most highly consumed vegetable due to its status as a basic ingredient in a large variety of raw cooked or processed foods. It belongs to the family of Solanaceae which includes several other commercially important species. Tomatoes are grown worldwide for local use or as an export crop. In 2014, the global area cultivated with tomato was 5million hectres with a production of 171million tonnes, the major tomato producing countries being the peoples Republic of China (hereafter “Chinia”) and India (FAOSTAT, 2017). Tomatoes can be grown in a variety of geographical zones in Open fields or greenhouse and the fruit can be harvested by manual or mechanical means under certain conditions (e.g rejuvenation pruning, weeding, irrigation, frost protection), this crop plant can be perennial or semi-perennial, but commercially it is considered an annual (Geisenberg and Stewart, 1986). Tomatoes are a perennial herbaceous plant but it is often grown as an annual crop even it biennial and perennial forms exist. Tomato is cultivated in tropical and temperate climates in open field or under greenhouse in temperature climate. Greenhouses are often used for large scale production. In warm climate with right light intensity for growth, around 45days are necessary from germination to anthesis and 90-100days to reach to beginning of fruit ripeness (Nuez, 2001).

The cultivated tomato is a number of the genus Solanum within the family Solanaceae, commonly known as right shade family, also includes other notable cultivated plants such as tobacco, chilli, pepper, potato and eggplant. The genus Solanum consists of approximately 1500 species. The tomato clade (section Lycopersecuun, formerly recognized as the genus Lycopersicon) includes the cultivated tomato (Solanum lycopersicum) and 12 wild relatives, all natives to Western South America. Tomato (Solanunnlycopersicum) is derived from two wild ancestor species, Solanum pimpinellifoliumand Solanum cerasiforme. Other wild species are useful for breeding disease resistance, color improvement and desirable quality traits (Ranc et al., 2008). The 12 wild members of the lycopersicum clade demonstrate a high level of phenotypic and genetic variation. Peralta, et al (2008) recognized 12 species of wild tomato, this was an increase on the 9 species of tomato recognize by Rick et al. (1990).

Tomatoes require a warm climate for growth and do not tolerate frost. The usual life cycle in cultivation spans one spring and summer. Its optimum temperature is around 20⁰C (day) and 12⁰C (night). Plants require minimum temperature above 18⁰C for vegetable growth but can survive a lower temperature (12⁰C). Temperature above 31⁰C reduces the rate of flower fertilization, plant development and fruit ripening (geisenberg and Swart, 1986).

Tomatoes grow well on most mineral soils, but they prefer deep, well-drained sandy loams. Deep tillage enables adequate rot penetration in heavy clay-types soils, thus allowing the production of tomato. Tomato is moderately tolerant to a wide range of P^H. Worely (1976) show that tomato yield was higher in soils with a P^H between 6.5 and 6.9 compared with that obtained in acidic soils. Tomatoes are widely consumed worldwide. It is a popular species preferred in gastronomy for its characteristic flavor. It is used in several traditional dishes because of its compatibility with other food ingredients and high nutritional value (2008). Tomatoes are currently an important food component globally. The tomatoes are in fact the second largest vegetable both in terms of production and consumption (FAO, 2016). Reports from the United States shows tomato as the second most consumed fresh vegetable with 6kg/person in 2017 (USDA, 2016). Tomatoes are known as a source of Vitamin and pro-Vitamin (Vitamin C, A, B, Carotein, Folate) minerals such as Potassium and secondary metabolites such as lycopene, flavonoid, phytosterols and polyphenols (Beecher, 1998 and Luthria et al., 2006) thus 100g of fresh tomato provides over 46%, 8% and 3.4% of daily requirements of Vitamin A (being 900UE), Vitamin C (being 82.5g) and Potassium (being 3500mg), respectively (Gebbhar and Thomas, 2002 and Canene-admas et al., 2005).

1.2     Statement of the Problem

The Vitamin C content in tomatoes is important to human health, but many at times its contents are reduced or destroyed completely on heating. When the amount of Vitamin “C” required by the body is not in the right amount, it causes a problem to the body system. Vitamin C deficiency can lead to a condition called scurvy poor wound healing, inflammation of the gums and increase chances of cancer. This study was carried out to ascertain the level of degradation of Vitamin C as a result of heat applied to it when using it in cooking food. Most people don’t seem to know the heat effect on Vitamin C content in the tomatoes they used in preparing their meals. This study will therefore serve as source of enlightenment to those that use tomatoes to prepare their meals, if they are to get the required Vitamin C content from it.

1.3     Aim and Objective of the Study

Vitamin C is an important nutrient to human health. The aim of this research is to determine the effect of heat on the Vitamin C content in some selected varieties of tomatoes grown in Pankshin/Kanke LGA of Plateau State. The specific objectives are:

1. Assess the Vitamin C content in five varieties of tomatoes
2. Assess the heat effect of Vitamin C content using different temperatures on the five varieties of tomatoes.
3. To use statistical analysis to ascertain the level of significant of the different temperatures on the five varieties of tomatoes

1.4     Research Question

The following questions listed below are to guide the research in carried out this research.

1. To what extent does cooking of tomatoes at high temperature result in the reduction of Vitamin C
2. To what extent does heat effect varies on Vitamin C in some varieties of tomatoes

1.5     Significance of the Study

The study will enlighten students on the importance of Vitamin C as regarding to human body function, human health and a necessary dietary source.

The study will enlighten Chef and cooks to know that for retention of vitamin C while cooking, it is recommended that the vegetables are cooked in low heat and small amounts of water for short periods to minimize the loss of vitamin C.

1.6     Limitation of the Study

This research is limited to determining the effect of heat on Vitamin C content in some selected species of tomatoes; this is because of some challenges such as financial problems and time constraint

1.7     Definition of Terms

The following are the key terms that the researcher use in the study, they are:

Effect: The change that something/somebody cause in something/somebody else.

Heat: The quality of being hot. The level of temperature

Content: Is the amount of things that are contained in something

Vitamin: A natural substance in food that is an essential part of human and animal, eat to help them grown and help them stay healthy

Varieties:The quality or state of having different forms or types.

Tomatoes: These are soft fruit with a lot of juice and shiny red skin that I eaten as a vegetable either raw or cooked.