Introduction

Fresh vegetables are important sources of nourishment and a vital ingredient in healthy and balanced diets. Fresh vegetables are highly recommended in any diet virtually without quantitative restriction and the roles of vegetables in maintenance of good health are well known (Osuagwe, 2008). Green leafy vegetables form an indispensable constituent of diet in Africa generally and west Africa in particular. Generally they are consumed as cooked compliments to the major stables like cassava, cocoyam, guinea corn, maize, millet, rice and plantain (Oguntona, 1998) they are noted to occupy an important place among the food crops as they provide adequate amount of vitamins and minerals for human. Vegetable are important as food both from economic and nutritional stand point. Their nutritive significance is their richness in minerals and vitamins which is essential is the maintenance of human health (Bolaji et al; 2008). The importance and awareness of nutrition is public health issues has resulted in the increase demand of knowledge of the biochemical nutrients of foods. They are good sources of carotene, ascorbic acid, riboflavin, folic acid and minerals like calcium, iron, and phosphorous (Fasuyi, 2006). Vegetables also contain phytochemical which are nutritionally and medicinally useful but atimes reduce the bioavailability of nutrients in human system (Fasuyi , 2006)

Vegetable are eaten raw or processed. Any methods selected for processing vegetables should be such that does not adversely affect the colour, texture, flavour, and nutritional values especially the vitamins and minerals (Edeoga et al; 2006) The processing method used for vegetables therefore depends on the end product desired and storage facilities available (Cruess, 1985).Water leaf (Talinum triagulare) is a highly perishable vegetable. It needs special processing methods to prevent decomposition. These processing methods either change the nature and constituents of the vegetable positively or negatively. This work is aimed to evaluate the minerals and phytochemicals in water leaf (Talinum triagulare) as affected by commonly practiced food processing methods of sun drying steam blanching and combination of the two methods.

Materials And Methods

Collection of plant materials: Fresh leaves of water leaf (Talium triagulare) were harvested from a nearly farm within the Rufus Giwa Polytechnic, Owo, Ondo State.

Preparation of plant materials: The fresh leaves of water leaf (Talinum triagulare) were thoroughly cleansed. 50g of the fresh leaves of the vegetable was weighted in three places. The first part was sun dried for five days, the second part was steam blanched while the third part was steam blanched and sun dried for 3 days.

Determination of minerals and phytochemicals: The mineral content of samples were analysed by AOAC method (1990) using the Atomic absorption spectrophotometer. The method of Brunner (1984) was used for Saponin determination. Tannin was determined by method of Wang and Hang (1993). The method of Maga (1982) was used for phytate determination while the method of Association of official Analytical chemists AOAC (1990) was used for oxalate and alkaloid.

Results And Discussion

Table 1 showed the percentage mineral content of the water leaf (Talinum triagulare) subjected to three different processing methods. The result showed that the values of the minerals (sodium, Potassium, calcium, magnesium and iron) were highest in the sundried samples. The method has 0.0492%, 0.0463%, 0.0479%, 0.0246% and 0.0035% for Na, K, Ca, Mg and Fe respectively. The combined methods have 0.0483%, 0.0418%, 0.0472%, 0.0192% 0.0034% for Na, K, Ca, Mg and Fe respectively. It could be deduced that the sun drying method and the combined methods show the best means of retaining the mineral content of water leaf if there is need to use these processing methods. Since sodium and potassium are important intercellular and extra cellular cation. The Na and K ratio are important in determine the health status of an individual. A ratio of less than 1 has been recommended to prevent high blood pressure (FND, 2002).

Figure 1

Table 1: Mineral Content Of Water Leaf () Subjected To Different Precessing Methods

The processing methods produce Na and K ratio less than 1 which is in accordance with the recommended ratio. The result of this work showed that sun drying is the best method among these methods when high level of these minerals are desirable which conforms with the work of Akubgwe et al (2008) on other vegetable.

Calcium is a mineral important in teeth, bone and muscle metabolism (Turan, 2003) According to shills and Yong (1988), a good food calcium content is greater than 1 and poor if less than 0.5. From the result, the vegetable was rated a poor calcium food. This implies that the processing methods did not improve the food values of the plant. The processing methods used for vegetables therefore depend on the end product desired and storage facilities available (Cruess, 1985). Magnesium is an important mineral element in connection with circulatory disease such as heat disease (Akubgwu et al; 2008) while iron is an essential trace element for heamoglobin formation, normal function for central nervous system and energy metabolism (Ishidu et al; 2000) there was a great reduction in these two mineral elements in the water leaf.

Table 2 showed the phytochemical content of the water leaf subjected to different processing methods. The sun dried vegetable has 2.200 (mg/g) Saponin, 0.432 (mg/g) phytate, 2.775 (mg/g) Oxalate, and 4.800 (mg/g) alkaloid. Steam blanched sample has 1.400 (mg/g), 0.406 (mg/g), 3.600 (mg/g) and 5.200 (mg/g) Saponin, phytate, oxalate, and alkaloid respectively while in the combined methods sample, Saponin was 1.780 (mg/g). Phytate was 0.497 (mg/g), oxalate was 3.160 (mg/g) and alkaloid 5.20 (mg/g).

Figure 2

Table 2: Phytochemical content of water leaf ( subjected to different precessing methods

Dupont et al (2000), reported similar variation in the phytochemical content of lettuce subjected to a variety of processing methods. The presence of these phytochemicals has been attributed to the bioactive principles responsible for ethnopharmalological activities of most medicinal plant (Edeoga et al; 2005). This dictates why efforts have been expanded in studies aimed at elucidating their levels in medicinal plant (Edeoga et al; 2006).Aletor (1993) also showed similar result with his researches in other vegetables. The medicinal values of plants and vegetables are dictated by their phytochemicals and other chemical constituents (Fallah, et al 2005)

The presence of minerals and phytochemicals in waterleaf explain the nutritional and the medicinal use of the vegetable. All the processing methods showed a considerable reduction in the minerals and phytochemical content of the vegetable but sun drying is the most preferred processing method to retain the best of the minerals and phytochemicals screened for over steam blanching and the combination of these methods.

Correspondence to

IBRAHIM Tesleem A. Department of Food Science and Technology, RUFUS GIWA POLYTECHNIC P. M. B 1019, OWO, ONDO STATE, NIGERIA Telephone number: 2348035774200 e-mail: tessieuptown@yahoo.ca