Food Science and Technology Project Topics

Mineral Composition of Fermented and Unfermented Sweet Potato-pigeon Pea Weaning Food

Mineral Composition of Fermented and Unfermented Sweet Potato-pigeon Pea Weaning Food

Mineral Composition of Fermented and Unfermented Sweet Potato-pigeon Pea Weaning Food

Chapter One

Aim and Objective of the Study

Thus, the aim of this study was to determine the mineral composition of fermented and unfermented sweet potato- pigeon pea weaning food.

Objectives are:

  1. to produce fermented and unfermented sweet potato-pigeon pea flour
  2. to evaluate mineral composition of the samples



Sweet Potato (Ipomoea batatas L.)

Ipomoea batatas is the sixth most important food crop in the world and ranked seventh in the total world food production after wheat, maize, rice, potato, barley, and cassava (Islam, 2006). I. batatas or commonly known as sweetpotato originated from the Central America and Mexico and has been dispersed worldwide due to its high yield potential and wide adaptability. Carolus Linnaeus was the first to give the scientific term Convolvulus batatas to the sweetpotato plant in 1753, referring to the plants grown in George Clifford’s garden in the Netherlands.

Ipomoea batatas is a perennial herbaceous dicotyledonous species and is categorised under the Convolvulaceae family, which includes the morning glory (I. purpurae) plant and can be further divided into varieties or cultivars. From the group of approximately 50 genera and more than 100 species in this family, I. batatas is the only group that has major economic importance as food (Woolfe, 2002). Besides I. batatas, Ipomoea aquatica (known locally as Kangkong) is also grown for human consumption and eaten as dishes in China and Malaysia. The increased numbers of Ipomoea batatas varieties took place due to selection by human for domestication. I. batatas is cultivated in more than 100 countries and is an extremely important food crop in developing countries (Wang, 2005). Besides that, the I. batatas are also well adapted to tropical areas where high proportion of poorest people in the world lived.

  1. batatas (sweetpotato), unlike Solanum tuberosum (potato) are not tuber propagated. A tuber can be defined as short, thickened-stem of an underground branch (Kakaty et al., 2002). In contrast, I. batatas produces primary fibrous roots, pencil roots and storage roots and they lack of merismatic buds. The storage roots are attached to the stem by a stalk of thinner roots that is usually initiated at the stem node just below the soil line. Worldwide currently, there are over 6000 varieties of I. batatas and they are basically distinguished by skin colour, flesh colour, and some, by origin (ICP, 2006). The skin colour of I. batatas storage roots typically range from white to brown to red-orange while the flesh colour may be red-orange, orange, yellow or white (more common). Besides that, the flesh of the storage roots can be either soft or firm.

Distribution and Growth Habitat of Ipomoea batatas

Scientists believed that Ipomoea batatas was domesticated more than 5000 years ago. Recent evidence showed that Ipomoea batatas was originated from Central-America although contradicting reports claimed that it was from South America (Natural History Museum, 2007). Ipomoea batatas was widely established in the Americas by the time Europeans first arrived there and was spread to the Old World through various routes. Due to its hardy nature and broad adaptability, Ipomoea batatas successfully spread through Asia and Africa during the 17th and 18th centuries. According to FAOSTAT data, approximately eight million hectares of land were harvested resulting in approximately 107 million tons of Ipomoea batatas roots from more than 100 countries in the year 2010 alone (FAOSTAT, 2012).

Asia is the world’s largest sweetpotato producing region with an annual production of approximately 88 million tons and China contributes about 80% of this amount. Nearly half of these productions were used as animal feed while the remaining was used for human consumption. In contrast, the African region produced about 14 million tons of Ipomoea batatas roots annually but most of this crop is cultivated for human consumption (FAOSTAT, 2012). Previous research on Ipomoea batatas has been focusing on the yield and nutrient improvements in the storage roots although both the Ipomoea batatas roots and tops possess a variety of compounds which are beneficial to human health.

Classification and Taxonomy of Ipomoea batatas

The long-term cultivation and selection of Ipomoea batatas produced many different varieties with different roots skin colours, flesh colours and shapes. Variations can occur both naturally as a result of mutations which will be termed cultivar or through hybridisation by human (known as varieties) (Morton, 2001). Through the advances in biotechnology, Ipomoea batatas roots have been developed for special purposes such as for their high protein, starch or β-carotene contents. Ipomoea batatas varieties are usually distinguished by the size and colour of their fruits. The examples of Ipomoea batatas varieties are Kotobuki (Japanese), Georgia Jet, Fernandez, Red Jewel and Okinawa. Ipomoea batatas can be planted for either their roots and/or forage production, in which yields often depended on the different climate, season and soil conditions (Hartemink et al., 2000; Woolfe, 2002; Antia et al., 2006).

Ipomoea batatas is located in the plant kingdom and belongs to the “Convolvulaceae” family, Ipomoea genus and batatas species and thus termed Ipomoea batatas. While the current method of identification focused on the variations of storage roots to distinguish the Ipomoea batatas varieties, it was found to be time consuming and required the formation of the roots before the different varieties can be identified. Therefore, the leaf of the plant was subsequently used as a new way to distinguish between the different varieties. This method is an economical way to overcome the drawbacks of the previous identification method. Leaves are commonly distinguished based on parameters such as length, width, shape, margin and venation. McEwen (2004) pointed out the variation in the Ipomoea batatas leaves in terms of shape namely cordate shaped with heavily divided single lobed and palmate shaped with seven lobes or more.

Growth and Usages of Ipomoea batatas

Ipomoea batatas is considered to be a small farmer crop but grow well under many farming conditions. The advantages of growing this crop include the following: it has a relatively few natural enemies, it requires little or no pesticide, it can be grown in soil with little fertilizer, it has a high tolerant to weeds and is easy to plant compared to other tropical leafy vegetables (Islam, 2006). Furthermore, Ipomoea batatas can be grown throughout the year and therefore provide a continuous supply to industries. Ipomoea batatas root is a rich source of carbohydrate and therefore can help curb famine when there is a rice shortage crisis. In some countries, excess storage roots are used to feed poultry besides human (Ruiz et al., 2000). The storage roots can be harvested within 3 to 6 months and are well adapted to warm tropical lowlands. The Ipomoea batatas can be propagated in two ways: by tuber and cuttings. Although naturally resistant to pest, destructions by sweet potato weevil and viruses diseases are the most common problem encountered in Ipomoea batatas plantation (CGIAR, 2005).

Ipomoea batatas leaves contained high amount of pro-vitamin and was found to be on par with cassava and green leafy vegetables, hence owing them the term “pro-vitamin rich vegetable”. Modern biotechnology has been used to produce varieties with a high level of pro-vitamin that can have measureable effects on both human health and nutritional status (Kimura et al., 2005). With the recent advancement in the field of biotechnology, Ipomoea batatas are currently used in Africa to combat Vitamin A deficiency that causes blindness and death of 250 000 to 500 000 African children annually. From this total, about two third of these children suffered from xerophthalmia, and die within a year after losing their sight. Although Ipomoea batatas was a staple food for a long time in Africa, their storage roots, which mostly white flesh, contains no β-carotene which is an important precursor of Vitamin A (CGIAR, 2005).





Sweet potato (Ipomoea batatas) and Pigeon pea (Cajanus cajam) used in the research work was purchased from a local market in Owo, Ondo State. The samples were processed in Food Processing Laboratory, Rufus Giwa Polytechnic Owo, Ondo State, Nigeria


  Preparation of fermented sweet potato-pigeon pea flour

Fresh sweet potato root were washed, peeled, sliced and pigeon pea seeds were winnowed, sorted, drained. The two cleaned samples (sliced sweet potato root and washed pigeon pea were soaked together i.e fermented together for 72 hours. After 72 hours the fermented samples it was washed, wet milled, sieved, sedimented for 24 hours, drained, sun dried for 3 days and dry milled into powder, sieved and packaged in airtight container for further analysis (Fig. 1).




Table 4.1: Mineral composition of fermented and unfermented sweet potato-pigeon pea weaning food




The present research study was on “mineral composition of fermented and unfermented sweet potato-pigeon pea weaning food”. Mineral composition of the weaning food samples revealed that the fermented sample of weaning food is higher in all the mineral contents (Sodium, potassium, calcium, iron, manganese, phosphorus and zinc) than that of unfermented sample of weaning food. Potassium, sodium, calcium and zinc was observed to have highest values (greater than 2 mg/100g) while the copper, iron, manganese and zinc has the least mineral content in both samples. This indicate that the blends of sweet potato and pigeon pea flour contain can be a good source of potassium, sodium, calcium and zinc. In conclusion, the fermented sample of weaning from sweet potato-pigeon pea is of good minerals source than unfermented sample of weaning from sweet potato-pigeon pea.


            Based on the findings of this study, it is therefore recommended that food industries especially food industries that specialize in the production of infant food should take into consideration of using sweet potato and pigeon pea for the production of infant or complementary food. This can help control nutrient (micronutrient) malnutrition in infant in Nigeria at low cost.


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