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This chapter covers carbohydrates, the most abundant class of biopolymers on Earth and significant components of water column particulate organic matter and dissolved organic matter in aquatic environments. Carbohydrates are important structural and storage molecules and are critical in the metabolism of terrestrial and aquatic organisms. Carbohydrates can be further divided into monosaccharides (simple sugars), disaccharides (two covalently linked monosaccharides), oligosaccharides (a few covalently linked monosaccharides), and polysaccharides (polymers made up of several mono- and disaccharide units). In phytoplankton, carbohydrates serve as important reservoirs of energy, structural support, and cellular signaling components. Carbohydrates make up approximately 20 to 40% of the cellular biomass in phytoplankton and 75% of the weight of vascular plants. Minor sugars, such as acidic sugars, amino sugars, and O-methyl sugars, tend to be more source-specific than major sugars and can potentially provide further information on the biogeochemical cycling of carbohydrates.

In traditional cuisine, soups and sauces are thickened with starch-based ingredients, such as wheat flour. Although it is possible to obtain a similar degree of thickening in soups and sauces with nonstarch polysaccharides—such as guar gum, xanthan gum, locust bean gum, and carboxymethylcellulose—the mouthfeel and flavor are often not as good as traditional starch-based ingredients. This chapter explains why this is so. Solutions of nonstarch polysaccharides have poor mixing behavior which results in the following: taste molecules, particularly salt and sugars, will remain in the poorly mixed solution and be swallowed before their concentration equilibrates with saliva in the mouth, resulting in inhibited saltiness or sweetness. If a viscous solution mixes poorly with saliva, it will dilute very slowly, giving an undesirable mouthfeel, which can be described, depending on the polysaccharide, as slimy, mouth coating, clingy, and the like.

Chapter 2 describes conversion of cellulose to useful products in the 19th century (rayon, celluloid, guncotton) and the role of glucose in its chemical structure. The preparation of candy floss (cotton candy) is described and how the method is relevant to spinning synthetic fibres. The composition of sugar and the composition of foods is explained. In particular, the distinction among starch, sugar, carbohydrates, monosaccharides, and polysaccharides is made. Conversion of crops to bioethanol is described.

Erosion can be controlled by four main means, that is, improving soil structure, covering soil with plants, covering soil with mulch, and using special structures. Soil structure is related to the soil tilth, or physical condition of a soil, with respect to ease of tillage or workability as shown by the fitness of a soil as a seedbed and the ease of root penetration. Other terms relating to soil structure improvement are soil aggregation and the formation of aggregates. Aggregates form when a cementing substance is present in a soil. The most important cementing substances in soil are soil polysaccharides and soil polyuronides produced as by-products from microorganisms during decomposition of organic matter. Other less important cementing substances in soil include clays, Ca, and Fe. Formation of aggregates results in improved water infiltration with reduction in erosion. Decomposition of organic matter in soils can be shown as an equation: . . . Plant and animal remains + O2 + soil microorganisms → CO2 + H2O + elements + humus + synthates + energy . . . The decomposition process has the following features: . . . 1. Oxygen is required; thus soil aeration is important. Anytime a soil is stirred or mixed by cultivation, spading, plowing, some organic matter decomposition occurs. 2. Readily available decomposable organic material is required for the microbes to work on. Green organic material, such as grass clippings, is an excellent substrate. 3. Many different types of soil microorganisms are involved in this process. Decomposition is more rapid in soils at pH 7 (neutral). 4. A product of organic decomposition is humus. Humus has many desirable features that improve a soil for plant growth. 5. Plant or animal remains are not effective in soil aggregation until they begin to decompose. 6. The more rapid the decomposition, the greater effect of soil aggregation. . . . Microbial synthates consist of polymers called “polysaccharides” and “polyuronides.” A polymer is a long-chain compound made up of single monomer units hooked together acting as a unit. The term “poly” means “many” and “saccharide” means “sugar.”