General characteristics of starch

A basic characteristic, common for all kinds of starch, is its aptitude to undergo hydrolysis. Because of this property it is one of the fundamental elements of the diet. 

In all types of starch small amounts of phosphorus are present owing to the part played by phosphoric compounds in the enzymatic processes of starch formation. Disregarding a few exceptions,.starch consists of two fundamental components  

From osmotic pressure measurements, the molecular weight of amylose has been determined as approximately 10,000-50,000. This value is well in line with the value estimated from the determination of the terminal functional groups. 

The molecular weight of amylopectin is appreciably higher, since according to osmotic pressure determinations it is 50,000-1,000,000. 

From the determination of the end groups, the long-chain molecules of amylopectin seem to be composed of 24-30 glucose units, from which it is concluded that the substance is a branched-chain carbohydrate. 

---

General characteristics of starch Physical properties of nitrosiarch... 

General Characteristics of Starch. The properties of starch are closely related to the existence of hydrogen bonds between the two strands of the double helix forming the crystalline zones. Interchain interactions ensure most of the cohesive properties of the system. However, due to the molecular structure, certain polymer-polymer interactions cannot be established and the cohesive energy density is definitely lower than that of native cellulose. 

This chapter reviews the general context of starch as a material. After a survey of the major sources of starch and their characteristic compositions in terms of amylase and amylopectin, the morphology of the granules and the techniques applied to disrupt them are critically examined. The use of starch for the production of polymeric materials covers the bulk of the chapter, including the major aspect of starch plasticization, the preparation and assessment of blends, the processing of thermoplastic starch (TPS), the problems associated with its degradation and the preparation of TPS composites and nanocomposites. The present and perspective applications of these biodegradable materials and the problems associated with their moisture sensitivity conclude this manuscript. 

Starch- and sugar-containing crops are quantitatively the most important products of today s agricultural system. Most of the existing biorefinery concepts are based on these plants and they are referred to as first-generation feedstock (vide supra), but they also constitute the backbone of human nutrition. General characteristics of this type of biorefinery are listed in Table 1.1. 

ITie work described in this chapter was initiated to determine the kinetics of enzymatic and microbial attack on blends containing starch and LDPE or starch, LDPE, and EAA. From the initial studies came a more general goal of identifying structural and compositional characteristics of blends (in general) that facilitate or retard degradation of the polysaccharide component. 

Tapioca starch consumption in industrial applications has been more related to economics than to any unique functionality. While some performance characteristics of tapioca starch are advantageous in several applications, it is generally used in nonfood applications close to the supply points, such as in Brazil, India and Southeast Asia. Non-food consumption of starch in North America and Europe is primarily from readily available sources in these areas, i.e. com, wheat and potatoes. 

---