1. Overview of modifications

Starch is the main polysaccharide used as food and ingredient or additive in the food industry. The main advantages over other polysaccharides are the low cost and renewable raw material, but even starch can be obtained from several natural sources or modified by engineering genetic, as the waxy starch of corn. It also has drawbacks such as: lower solubility usually in water, lower shear stress resistance, lower capacity to support thermal decomposition, and high retrogradation, and these issues limit the use on several temperatures and pH usually found on food system and industrial applications.

The native starch can be improved by means of physical, chemical, and ionic treatments. The physical treatments are cost-effective, are less labor intensive, and only have initial investment of equipment than the chemical treatments (Figure 1). The aim of physical treatment is to produce changes in the granular structure, and the common processes involved are heat moisture, annealing, and extrusion. However, today, there are novel processes like sonication and high hydraulic pressure. Figure 2 shows the main characteristics of these processes. This plot is an easy way to view and compare process conditions like moisture, temperature (glass and gelatinization), and the effect of treatment on granule structure and molecular weight. For example, after annealing process, the granular structure and molecular weight remains without change, and the moisture percent is similar that heat moisture processes employ, but the temperature of process is set between glass and gelatinization temperature.

The chemical modified starch has lot of reports in the literature compared with the other treatments; on this spectrum of chemical modifications, the starch molecules can reduce the molecular weight of chains, add functional groups like acetyl, or even oxidize OH groups present in the monomer of the starch polymers. The chemical treatments also can associate chains of starch like in cross-linked reaction or even make a web around the starch granule. Another step forward in the reactions, complexity of starch is graft copolymerization, which means adding synthetic monomers or polymers or semisynthetic polymers to the biopolymers of starch. Another interesting

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**Chapter 2**

**Provisional chapter**

**Chemical Modification of Starch with Synthetic**

**Chemical Modification of Starch with Synthetic**

DOI: 10.5772/intechopen.72384

An alternative for solving the environmental pollution problems generated by conventional plastics, it is the chemical modifications graft-type of the starch with synthetic polymers of post-consumer and in situ polymerizations on the starch granules. The starch modified by this methodology allows to counteract the disadvantages of both polymers such as the little or no biodegradability of the synthetic polymer and the poor mechanical properties of the starch. In the present study, a review on the chemical modification of starch with synthetic polymers by grafting is carried out. Factors affecting the copolymerization reactions of starch-g-synthetic polymer were analyzed, for example, their chemical nature, solubility, size and length of polymer chains, temperature, catalyst and starch/amylose content, as well as their characterization chemistry and the potentials applications of this copolymer.

Due to environmental pollution generated by conventional plastics such as polyethylene (PE), polypropylene (PP), vulcanized rubber, polystyrene (PS) and polyvinyl acetate (PVC), to name a few, several investigations have been carried out to generate materials that can compete or be an alternative to the excessive use of these plastics because these are not biodegradable. From this point of view, the use of natural polymers such as starch can contribute to reduce the negative impact of conventional plastics. However, materials made from starch alone generate plastics, which have important disadvantages such as their high affinity for moisture and poor mechanical properties. An alternative for solving these disadvantages is the chemical modifications of the starch with synthetic polymers of postconsumer and in situ polymerizations on the starch granules. These chemical modifications are called graft-type copolymerizations because the synthetic polymer chains are chemically bonded to the surface

**Keywords:** starch, synthetic polymer, graft copolymer, biodegradable

of the starch granule, as if these were hair extensions (**Figure 1**).

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

and reproduction in any medium, provided the original work is properly cited.

Aurelio Ramírez Hernández

**Abstract**

**1. Introduction**

Aurelio Ramírez Hernández

http://dx.doi.org/10.5772/intechopen.72384

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

Figure 1. Relative comparison of the physical and chemical treatments of starch.

Figure 2. Relative comparison of process conditions and its effect on granular structure for physical treatments of starch.

process to modify the starch is the ionizing radiation process. The radiation ionizing can come from UV, gamma, or accelerated electrons; at first instance, this process was used with synthetic polymers, but today it is used with starch. The radiation produces free radicals that react with starch polymers to produce different properties on the ionized polymers.
