CHAPTER ONE

1.0 INTRODUCTION

Sweet potato (Ipomoea batatas) is an extremely versatile and delicious vegetable that possesses high nutritional value (Mohanraj and Sivasankar

2014). Among the world's major food crops, sweet potato produces the highest amount of edible energy per hectare per day (Sukhcharn et al. 2008). Sweet potato consists of about 70% carbohydrates (dry basis) of which a major portion is starch, which can be utilized as a functional ingredient in certain food preparations (Avula 2005). It is an excellent source of vitamin A (in the form of beta - carotene) and also a very good source of vitamin C and Manganese. In addition, sweet potatoes are a good source of dietary fiber, natural sugars, protein, niacin, vitamin B5, vitamin B6, vitamin E, potassium, biotin, iron, calcium and copper (“The world healthiest foods”, 2017).

Sweet potato is commonly referred to as a subsistence, food security or famine relief crop. Its uses have diversified considerably in the developing countries. Sri Lanka has a long history of cultivation of sweet potatoes. It is considered as a crop of exotic origin, but people regard it as indigenous because it has been in cultivation in Sri Lanka as an important traditional food crop since ancient times (Karunathilake 2005). Options for sweet potato products are numerous, and based on recent diagnostic assessments carried out in developing countries, dried chips, starch and flour have been identified as among the most promising products (Collins 1989).

The raw material of foremost importance in bakery product is the wheat flour. Wheat is the main raw material for bakery, biscuit and paste (Diana et al. 2007). Bakery products are commonly made from wheat flour containing gluten, whereas gluten contributes to the typical texture, flavour and form of the usual bread and cake products. Without gluten, baked goods will not hold their shape. That is why wheat flour is used in baking. There is however circumstances in which wheat flour are not readily available, or if people in these areas nevertheless wish to change to the consumption of the bread so that they will need to import wheat and pay for it.

A mixture of wheat flour and sweet potato flour could make a good baking product, which should increase its economic value (Zuraida 2003). Most of the technical research on sweet potato flour focused on the development of new products using sweet potato flour rather than on efficient methods to produce and store the flour (Lizado and Guzman, 1982; Sukhcharn et al. 2008). Addition of various proportion of sweet potato flour in wheat flour can increase the nutritive values in terms of fiber and carotenoids and also helps in lowering the gluten level and prevent humans from coeliac disease (Tilman et al. 2003).

Sri Lanka has a long history of sweet potato cultivation. Extent and production of sweet potato are 3,270 hectares and 25,780 metric tons in 2010 (Department of Census and Statistics of Sri Lanka, 2010). Sweet potato can be grown successfully throughout the year in all agro-ecological zones. In Sri Lanka, they are cultivated in all the districts but mainly in Ratnapura, Hambantota, Kurunagale, Gampaha, Kagalle, Badulla and Kalutura districts. In dry zone the cultivation area of sweet potato is low compared to wet zone    and intermediate zone (Department of Census and Statistics of Sri Lanka, 2010). It is considered as a crop of exotic origin, but people regard it as indigenous because it has been in cultivation in Sri Lanka as an important traditional food crop from very ancient time (Karunathilake 2005).

Sweet potato based products are of high quality and could compete with the existing products in the market (Sneha et al. 2012). The use of sweet potato flour for supplementing with wheat flour in the bakery industry could substantially reduce the need for wheat being imported, reduce the usage of sugar on the products and increase the value of sweet potato. The objective of present study is to replace the wheat flour in cookies with sweet potato flour (gluten – free flours) in order to increase the fiber and other nutrients and develop cookies resembles as closely as possible to the wheat flour based product.

1.2 Sweet Potato Nutrition Facts

Sweet potatoes are high in many important nutrients. They contain a good amount of fiber as well as vitamin A, vitamin C, manganese and several other vitamins and minerals.

One medium cooked sweet potato contains approximately:

• 103 calories
• 23.6 grams carbohydrates
• 2.3 grams protein
• 0.2 gram fat
• 3.8 grams dietary fiber
• 21,907 international units vitamin A (438 percent DV)
• 22.3 miligrams vitamin C (37 percent DV)
• 0.6 milligram manganese (28 percent DV)
• 0.3 milligram vitamin B6 (16 percent DV)
• 541 milligrams potassium (15 percent DV)
• 1 milligram pantothenic acid (10 percent DV)
• 0.2 milligram copper (9 percent DV)
• 1.7 milligrams niacin (8 percent DV)
• 0.1 milligram thiamine (8 percent DV)
• 30.8 milligrams magnesium (8 percent DV)

In addition to the nutrients above, sweet potato nutrition also contains riboflavin, phosphorus, vitamin E, vitamin K, calcium and iron.

1.3 Sweet Potato Nutrition: Sweet Potato Benefits

1.     Stabilizes Blood Sugar

2.     High in Antioxidants

3.     Boosts Brain Function

4.     Enhances Immunity

5.     Promotes Vision Health

6.     Aids in Weight Loss

1. Stabilizes Blood Sugar

Sweet potatoes are an excellent dietary addition for those with diabetes as they have been shown to help reduce and regulate blood sugar levels. In fact, there are several studies focused on learning more about the connection between the sweet potato and diabetes. Caiapo, in particular, is a type of white sweet potato that has been studied extensively for its anti-diabetic properties.

In one study out of the University of Vienna in Austria, 61 participants with diabetes were given either four grams of Caiapo or a placebo daily for three months. At the end of the study, the sweet potato group had significantly lower blood sugar levels than the control group.

Another small study published in the journal Metabolism showed that treating diabetic patients with Caiapo for six weeks helped improve insulin sensitivity.  Insulin is the hormone responsible for the transport of sugar from the blood to the tissues where it can be used as energy. Improvements in insulin sensitivity allow it to work more efficiently in the body to maintain normal blood sugar.

Additionally, sweet potatoes are high in fiber, with each medium sweet potato fulfilling up to 15 percent of your fiber needs for the entire day. Fiber slows the absorption of sugar to help prevent spikes and crashes in blood sugar levels.

2. High in Antioxidants

Antioxidants are compounds that help fight off harmful free radicals to reduce the risk of chronic disease and prevent damage to the cells. Antioxidants may protect against diabetes, heart disease and even cancer.  Besides being rich in fiber and many important vitamins and minerals, sweet potatoes are also loaded with these beneficial antioxidants.

Orange-fleshed sweet potatoes are especially high in beta-carotene

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