QUALITY CHARACTERISTICS OF BISCUIT PRODUCED WITH WHEAT-SWEET POTATOES COMPOSITE FLOUR

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