Wheat and Rice – Ancient and Modern Cereals
Raymond Cooper, Jeffrey John Deakin in Natural Products of Silk Road Plants, 2020
White rice has had the bran and germ removed through the process of milling. White rice consists of just the endosperm layer, and it is almost entirely composed of starch. White rice grain consists of about 90% carbohydrate, 8% protein, and 2% fat but is low in fiber. Most of the available carbohydrate in rice grain is starch, which is broken down into glucose by enzymes in the human body to provide energy. There are two types of starch in rice grain: amylose and amylopectin, and they are shown in Figure 10.6. Both amylose and amylopectin are large carbohydrate polymers made of glucose molecules. The difference between them is that amylose has a straight chain, while amylopectin is highly branched. These are very large polymeric molecules, made up of a high number and/or a great variety of monosaccharides, and known as polysaccharides. Polysaccharides are a major source of metabolic energy, both for plants and for those animals, which depend on plants for food. Polysaccharides are a component of the energy transport compound, ATP. Starch is also a homopolysaccharide and only very partially soluble in water. Starch is the substance in which plants store their reserves of carbohydrate and is typically found in bulbs, tubers, and seeds. The main commercial sources of starch are found particularly in rice, and in wheat, maize, and potatoes. Starch is hydrolyzed and broken down in human metabolism to provide glucose.
Using iodine for analysis
Tatsuo Kaiho in Iodine Made Simple, 2017
Starch is a glucose polymer (d-glucose) comprises of approximately 20% liner polymer amylose and 80% amylopectin polymers with many branches. In the iodine-starch reaction, amylose molecules in the starch form a helical structure in the aqueous solution and turn bluish purple-reddish brown when iodine molecules are present. When the colored solution is heated, the iodine molecules are released from the helical structure, and the solution becomes colorless. However, when cooled, the helical structure is restored as iodine molecules return, and the solution regains its color. The iodine-starch reaction is well used in the educational field, and is always quoted in elementary, junior high, and high school science, chemistry and biology textbooks, as well as in food science textbooks. The iodine-starch reaction is used to verify the existence of starch from photosynthesis in plants leaves and to track the digestion and decomposition of starch by digestive enzymes. In addition, iodine plays a vital role in analytical chemistry. For example, the iodine titration is a typical titration method in volumetric analysis along with neutralization titration, oxidization–reduction titration, and precipitation titration [25].
Polysaccharide-Based Polymers in Cosmetics
E. Desmond Goddard, James V. Gruber in Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
Amylopectin is comprised of a central chain of repeating -glucose monosaccharides to which, in a random fashion, α-D- -glucose chains are attached through a -glucose linkage. This branching allows amylopectin to grow to enormous molecular weights within the granule, typically greater than Amylose is comprised of repeating -glucose monosaccharides and is, in fact, a diastereomeric allotrope of cellulose. Amylose is much lower in molecular weight than amylopectin, typically on the order of . It is a linear polysaccharide that can assume tight helices in solution.
Resistant starch, microbiome, and precision modulation
Published in Gut Microbes, 2021
Peter A. Dobranowski, Alain Stintzi
Starch is synthesized in the amyloplast and chloroplast organelles of plants, forming mixtures of amylose and amylopectin. These molecules both consist of chains of glucose subunits linked by α-1,4- and α-1,6-glycosidic bonds, but differ in their chain length (i.e. degree of polymerization; DP) and branching (α-1,6 bonds). Amylose possesses a DP below 6,300 glucose subunits, almost entirely (>99.3%) bonded by α-1,4-glycosidic linkages.16 Conversely, amylopectin forms much larger molecules (DP up to 26,500) with dense networks of short chains (mean DP 15–18) branching from longer chains (mean DP 48 to 60).16 The intra- and intermolecular interactions of amylose and amylopectin impart starch granules with a complex hierarchical structure (Figure 1).
Cassava toxicity, detoxification and its food applications: a review
Published in Toxin Reviews, 2021
Anil Panghal, Claudia Munezero, Paras Sharma, Navnidhi Chhikara
In cassava, majority of the starch is stored within amyloplasts in the thickened root. The starch content in roots varies from 73.7% to 84.9% on dry weight basis (Asaoka et al.1991). Amylose varies from 13.6 to 23.8% and amylopectin is about 83%. The content of soluble amylose (which is thought to be responsible for cohesiveness in cooked starch) of cassava was found in range from 10 to 40% of total amylose. Water absorption capacity and swelling power of starch are essential parameter for its viscosity and textural attributes in finished product. Cassava starch has good potential as food industry base product due to its high viscosity, low tendency for retrogradation, low gelatinization temperature, and also the absence of the undesirable flavors found in many cereal starches (Demiate and Kotovicz 2011). The starch obtained from fresh roots is having more swelling power than the one obtained from dried roots, therefore have better textural and viscosity attributes of finished products (Zhu 2015). Moreno and Gourdji (2015) reported that high rainfall leading to humid conditions results in sprouting causing the translocation of photoassimilates from the roots to the top and thus declining both dry matter and starch content of the roots.
Preparation and characterization of co-processed starch/MCC/chitin hydrophilic polymers onto magnesium silicate
Published in Pharmaceutical Development and Technology, 2019
Shereen M. Assaf, Mai Subhi Khanfar, Ahmed Bassam Farhan, Iyad Said Rashid, Adnan Ali Badwan
Moisture sorption isotherms of the studied polymers and a representative polymer-co-precipitate are presented in Figure 4. The moisture sorption of all polymers increased as the relative humidity increased. Chitin showed the highest moisture sorption followed by MCC and then starch. This is attributed to the high hydrophilicity of chitin with a large number of hydroxyl groups in addition to the flexible structure of chitin, which allows for deep penetration of water molecules inside its polymer chains (Rana et al. 2009). With respect to MCC, the strong intra- and inter- molecular hydrogen bonds and its rigid β(1–4) glucosidic bonds are responsible for the low interaction between the polar groups of MCC chain with water molecules (Bravo-Osuna et al. 2005; He and Fan 2007, Zhu et al. 2008, Builders et al. 2009). On the other hand, starch has less hydrophilic activity due to the crystalline nature of amylopectin, which comprises 70–80% of starch molecular structure.