Vegetable resources starch

This chapter gives a general introduction to the book and describes briefly the context for which the editors established its contents and explains why certain topics were excluded from it. It covers the main raw materials based on vegetable resources, namely (i) wood and its main components cellulose, lignin, hemicelluloses, tannins, rosins and terpenes, as well as species-speciflc constituents, like natural rubber and suberin and (ii) annual plants as sources of starch, vegetable oils, hemicelluloses, mono and disaccharides and algae. Then, the main animal biomass constituents are briefly described, with particular emphasis on chitin, chitosan, proteins and cellulose whiskers from molluscs. Finally, bacterial polymers such as poly(hydroxyalkanoates) and bacterial cellulose are evoked. For each relevant renewable source, this survey alerts the reader to the corresponding chapter in the book. 

Polysaccharides are macromolecules which make up a large part of the bulk of the vegetable kingdom. Cellulose and starch are, respectively, the first and second most abundant organic compounds in plants. The former is present in leaves and grasses the latter in fruits, stems, and roots. Because of their abundance in nature and because of contemporary interest in renewable resources, there is a great deal of interest in these compounds. Both cellulose and starch are hydrolyzed by acids to D-glucose, the repeat unit in both polymer chains. 

Biomass production on Earth corresponds to around 120,000 Mt per year. However, only 5% of that biomass is captured and used by hirmans, and of those 6,000 Mt, only 5% is not destined for energy or food usage. Thus, 300 Mt are already used for chemistry. Yet these quantities are fairly close to the 500 Mt of fossil resomces used annually for chemistry, so we can see the significant potential for substitution of fossil resources by increasing use of renewable resources. The resomces ttsed essential are starch and its derivatives - sugar, ethanol, etc. - cellulose, vegetable oil and glycerol, plant fibers, etc. 

Starch is a natural product from renewable resources, produced during photosynthesis as food reserve for plants and vegetables. It is the second most abundant biomass material in nature. It is found in plant roots, stalks, and crop seeds. The most important industrial starch sources are crops such as corn, wheat, potato, tapioca and rice. By refining these crops several byproducts can be obtained such as oil, bran, gluten, dextrin, sugar (glucose, fructose, HFCS), ethanol (for beverages and bio-fuels) and starch. 

The biorefinery concept that has emerged is analogous to today s petroleum refineries. However, many current endeavors focus on single technologies and feedstock such as starch or vegetable oils that could compete with food or feed. We need to create flexible, zero-waste biorefineries that can accept a variety of low-value local feedstock. Biorefineries will then be able to compete with existing industries (Clark et al., 2012). Further down the value chain the development of green chemistry fills the gap between the sustainable resource and the product (Poliakoff and License, 2007). 

Most types of Hot melt adhesives used in the mannfacture of laminates and in rapid Packaging industry applications are mineral oil-derived, hydrophobic and essentially non-dispersible, so they cannot be considered as renewable. However, some basic polymers have been prepared over the last decade from vegetable sources, which are renewable, and are adhesive, although these properties have limitations. These include poly(hydro-xybutyrate/hydroxyvalerate) (PHBV), poly(lactide) (which has poor thermal stability), and starch esters. Adhesives based on sulphonated polyesters with polar petroleum waxes have improved adhesion and adequate water dispersibility. In general, however, the perfect adhesive from renewable resources with satisfactory adhesion properties remains to be discovered. 

Processes and products developed to produce industrial materials from renewable resources have been too numerous to record here. For competitive reasons — supply of raw materials and technical and economic considerations — some of the products have varied widely in industrial use. Major U.S. industrial consumption of renewable resources have recently included oils and fats (animal and vegetable) industrial alcohol (wheat, corn, grain sorghum) fibers (cotton lint, flax, hides and skins) paper (forest products) isolated proteins (milk casein, animal glues, soybean, corn) turpentine and rosin (naval stores) and other chemicals (monosodiiim glutamate--wheat starch and dextrin—corn lactose—milk molasses and pulp residues --sugarcane and beet tannin lecithin pectin furfural). 

Over the last 25 years a number of biopolymeric materials entered the market place that are based on renewable resources and are compostable. Especially cellulose, starch, sugar, vegetable oils and their secondary products, as well as some lignins and proteins are renewable resources that have been used as base components for bio-based and biodegradable biopolymers. 

Polymers based on renewable resources from the agriculture feedstock include among the others polysaccharides, such as cellulose, starch, lignin and vegetable proteins, natural rubbers, and microbial polyesters, such as polyhydroxyalkanoates (PHAs). 

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