**1. Introduction**

Starch or amylum can be defined as a polysaccharide carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds [1]. It comprises of two main components which are mainly linear amylose and highly branched amylopectin. It exists as a stored discrete semi crystalline granules in higher plants [2]. Starch is an important energy source for humans, produced by all green plant as an energy store [2]. Its production in the chloroplast occurs in the daylight and it was rapidly produced by plants. However, glucose chain produced biochemically by photosynthesis in plant cells is responsible for the synthesis of starch [3].

Amylose contains 1–4 D-glucopyranosyl units and it constitutes about 15–30% of common starch, while amylopectin possesses a large number of short chains linked together at their reducing end side by 1–6 glucosidic linkage [4, 5]. However, the formation of crystalline lamella in starch is linked to amylopectin and their branching points are part of the amorphous nature [6]. Starch is regarded as a semi crystalline entity because of the presence of amorphous and crystalline regions in starch granules [7]. Starch also contains some minor components such as lipids and proteins aside amylase and amylopectin. The sizes of starch granules range from 1 to 100 mm, while its shape and composition depends on their botanical source [8].

Starch is derived from a range of raw materials such as corn, wheat, pea, potato, and cassava roots [9] and it has a wide range of applications beyond the food industry. It is also used in the paper/board sector for wet-end addition, size press, surface coating and in the production of recycled paper. It is also used as a binding agent in the pharmaceuticals sector, as an adhesive in industrial binding sector and as a stiffener in the textile sector [10]. Other non food applications of starch include utilization as alcohol-based fuel, low-calorie substitutes, biodegradable packaging materials, thin films and thermoplastic materials with improved thermal and mechanical properties [5].

Starch is the basis of our food and industrial economy, but the food situation in most developing tropical countries is alarmingly worsening owing to increasing population and shortage of fertile land [11]. The shortage of food supply has resulted into a high incidence of hunger and malnutrition [12, 13]. It also affected the demand for starch as food, pharmaceutical and industrial uses coupled with the need to attain self-sufficiency in starch production. However, the focus of this review is to critically appraise the challenges that food and allied industries are facing on the utilization of starch as their major raw materials and to suggest possible way outs.
