Biopolymer Phosphates

Starch phosphates are anionic polymers which are being used increasingly in food manufacturing since they promote thickening without gelling taking place. They also prevent clouding of canned food or separation of frozen foods when thawed. 

Starch phosphates with a fairly low degree of -OPO3 substitution for -OH, are obtained by heating starch with phosphoric acid at about 60°C. Starches from com, wheat or rice (the main sources) are usually not phosphorylated, but some natural varieties such as potato starch already contain a few phosphate ester groups (up to about 0.1% P) (Chapter 10.1). 

Sodium dihydrogen phosphate reacts with starch to give a monoester salt (12.22), while sodium trimetaphosphate reacts to produce a cross-linked diester (12.23). Cross-linked varieties of this kind are more stable towards heat, agitation and acidity than monoester salts. 

Cold-water gel starch is used for instant puddings and pie fillings [66]. This variety is made from a slurry of starch with NaH2P04 and Na2HP04 at pH 6.0-6.5, filtering and heating in vacuo at 60°C. The degree of phosphorylation is, however, rather low and the product contains less than 1% phosphate. 

Cornstarch processed with cyclic sodium trimetaphosphate is used to make cold-water jellies. Phosphorylated varieties of this kind are resistant to hydrolysis and degradation (probably due to cross-linking), and are used as thickening agents in cooked foods. 

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Biopolymer phosphates - casein, lactalbumin phosphate, starch phosphates, lecithin... 

Nucleic acids are acidic substances present m the nuclei of cells and were known long before anyone suspected they were the primary substances involved m the storage transmission and processing of genetic information There are two kinds of nucleic acids ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) Both are complicated biopolymers based on three structural units a carbohydrate a phosphate ester linkage between carbohydrates and a heterocyclic aromatic compound The heterocyclic aro matic compounds are referred to as purine and pyrimidine bases We 11 begin with them and follow the structural thread... 

Just as proteins are biopolymers made of amino acids, nucleic acids are biopolv-mers made of nucleotides joined together to form a long chain. Each nucleotide is composed of a nucleoside bonded to a phosphate group, and each nucleoside is composed of an aldopentose sugar linked through its anomeric carbon to the nitrogen atom of a heterocyclic purine or pyrimidine base. 

Deoxyribonucleic acid (DNA) (Section 28.1) The biopolymer consisting of deoxyribonucleotide units linked together through phosphate-sugar bonds. Found in the nucleus of cells, DNA contains an organism s genetic information. 

Owing to the weak hydrophobicity of the PEO stationary phases and reversibility of the protein adsorption, some advantages of these columns could be expected for the isolation of labile and high-molecular weight biopolymers. Miller et al. [61] found that labile mitochondrial matrix enzymes — ornitine trans-carbomoylase and carbomoyl phosphate synthetase (M = 165 kDa) could be efficiently isolated by means of hydrophobic interaction chromatography from the crude extract. 

The phosphate group is derived from phosphoric acid (H3 PO4) by replacing an O—H bond by an O—C or O— P bond. Phosphate is an important functional group in biochemistry, being involved in cellular energy production as well as acting as an important monomer in biopolymers, particularly in DNA. Bonds to phosphate groups form or break in the course of a number of important biochemical reactions. 

The nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), which carry embedded in their complex molecules the genetic information that characterizes every organism, are found in virtually all living cells. Their molecules are very large and complex biopolymers made up basically of monomeric units known as nucleotides. Thus DNA and RNA are said to be polynucleotides. The nucleotides are made up of three bonded (linked) components a sugar, a nitrogenous base, and one or more phosphate groups ... 

It is necessary to remember that as well as organic cross-links, elements such as boron, silicon and calcium cross-link all the major external proteins and saccharides even in the walls of prokaryotes. Many of the cross-linking binding sites are of oxidised side chains of biopolymers. As described in Section 8.10, certain of these elements form mineral deposits but now these minerals are frequently found inside the multi-cellular organisms. Here, we see a great difference between the chemo-types of plants and animals. The acidity of the extracellular fluids of plants differs from the neutral fluid of animals. It is not possible to precipitate calcium carbonates (shells) or phosphates (bones) in plants due to the weak acid character of these anions (see Table 8.12). Plants therefore precipitate silica and calcium... 

Phosphate ions are constituent parts of two universally found biopolymers, DNA and RNA. Phosphate ion is found in membrane lipids (phospholipids) and associated with the metabolism of many small molecules. The binding of dioxygen by hemoglobin is regulated by local concentrations of H+ (known as the Bohr effect), CO2 concentration, and organic phosphates such as diphos-phoglycerate (DPG), whose structure is shown in Figure 5.1. ... 

Nature itself gives us a spectacular example of a biopolymer-based delivery system in the form of the native casein micelle of mammalian milk (Lemay et al, 2007). This is primarily a colloidal delivery system for calcium, where the micronutrient is in the form of calcium phosphate, which does not give a bitter taste, and which provides good bioavailability owing to its colloidal size, amorphous state and quick dissolution in gastric conditions (pH 1-2). Nevertheless, the casein micelle structure is unique there are no other readily available natural delivery systems for most nutraceuticals. Therefore some new designs are clearly required (Velikov and Pelan, 2008 McClements et al, 2008, 2009). 

Cheese - [DAIRY SUBSTITUTES] (Vol 7) - [ELECTROSEPARATIONS-ELECTRODIALYSIS] (Vol9) - [GENETICENGINEERING - MICROBES] (Vol 12) - [MILK AND MILK PRODUCTS] (Vol 16) -analysis of [BIOPOLYMERS - ANALYTICALTECHNIQUES] (Vol 4) -antibiotics m mfg of [ANTIBIOTICS - PEPTIDES] (Vol 3) -disodiumphosphatem prdn of [PHOSPHORIC ACID AND PHOSPHATES] (Vol 18) -food additives for [FOOD ADDITIVES] (Vol 11) -mineral nutrient source [MINERAL NUTRIENTS] (Vol 16) -recombinant chymosm m [GENETIC ENGINEERING - MICROBES] (Vol 12)... 

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