Proximate constituents

Table I. Concentration of proximate constituents and carbohydrates in flours, dry and wet processed products from dehulled field pea and fababean, % dry basis.

In one case, therefore, triple silicates are the proximate constituents of the glass in the others, double silicates. In foot, the proportions of the three essential constituents, namely, silica, potassa, and oxide of lead, vary according as the melting furnace is heated with wood or coal. In the latter case, the proportion of oxide of lead is increased. The following analysis by Dumas has been already given at page 192, but is here repeated, to show the proportion of oxygen in the bases, as compared with that of the silica or silicic acid.—... 

These three earths or terrae are also the constituents from which animal and vegetable substances are composed, but their proximate constituents are more complex than in the minerals. 

Hamdy, A. E. A., and Dawes, C. J. 1988. Proximate constituents and lipid chemistry in two species of sargassum from west coast of Florida. Botanica Marina., 31,79-81. 

The precision of this and other equations can be assessed from their residual standard deviations (rsd). The ME equation based on proximate constituents (rsd 0.54) is less precise than the DE equation based on modern analytical components... 

Vauquelin, partly in collaboration with Fourcroy, discovered several important organic compounds. They distinguished a number of proximate constituents Yourcroy %principes immediats) in vegetables, such as acids, oils, camphor, gum, resin, tannin, starch, fibre, cork, caoutchouc, and extractive (a product of extraction with cold water and evaporation). Several definite compounds which had previously been obtained but the existence of which was in doubt were confirmed. Among these was malic acid and its salts. Sodium malate (with other salts of organic acids) was obtained by Donald Monro in 1767 and the acid from apples by Scheele in 1785 (see p. 232). The acid and its salts were studied by Fourcroy and Vauquelin. Vauquelin showed that the sorbic acid isolated from mountain-ash berries by Donovan is malic acid (the modern sorbic acid is a different substance) Vauquelin s elementary analysis of malic acid was inaccurate. 

No information has yet been reported on the precise role of ATP in the glutathione, as in the glutamine synthesis from its proximate constituents. 

The lipid in muscle is composed primarily of triglycerides (depot fats) and of phospholipids (membrane components), and is a constituent which varies enormously not only in amount present, but also in properties such as degree of saturation (species dependent). The ash of lean meat is comprised of various minerals such as phosphorus, potassium, sodium, magnesium, calcium, iron and zinc Carbohydrate was not noted in the proximate composition because while some may be present, it is normally there in low concentration compared to the other constituents. Glycogen is the carbohydrate occurring in greatest concentration in muscle but is normally degraded soon after the animal is sacrificed. 

In order to define this variety of food matrices, chemical composition differences that primarily influence chemical analytical measurements have to be considered. Major food components determining basic chemical make-up are the proximate composition of fat, protein, carbohydrate, ash, and moisture. Variations in ash content in general have a minor influence on analytical methods for other constituents and impact of moisture content can be controlled. Thus the major components influencing analytical performance are the relative levels of fat, protein, and carbohydrate. 

Southgate (1987) discusses the range of available RMs in terms of their fat, protein, and carbohydrate content. These constituents are presented graphically via a triangle wherein the relative position of each of these three proximate components is represented as 100 % at a separate apex and o % at the opposite side of an equilateral triangle as shown in Figure 6.1. 

The composition of coal is conveyed by representing its proximate and ultimate analysis. The former implies determination of contents of moisture, volatile matter, fixed carbon, and ash, while the latter implies total carbon, hydrogen, oxygen, nitrogen, sulfur and ash. Here, an account will be provided of the constituents of coal, moisture, volatile matter, ash, fixed carbon, and some miscellaneous components. 

In Section 4.3, some factors which need to be considered in choosing a method of analysis were discussed in general terms. The next step is to consider the properties of a method that will enable a choice to be made. This is done for a specific case, e.g. the determination of residues of chemicals used in veterinary practice to treat animal diseases and to prevent the development and spread of disease where large numbers of animals are kept in close proximity to each other. Such chemicals may be administered by injection, or orally as a constituent of the feed. Some chemicals are metabolized and excreted while others may be partially retained in edible products such as milk, eggs, meat and offal (liver or kidney). The detection and determination of such residues is a very difficult analytical problem. 

The interaction between melittin (a 26 a.a. peptide that exhibits potent anti-microbial activity)90 92 and lipopolysaccharides (the major constituent of the outer membrane of the Gram-negative bacteria) has been studied by NMR. It was demonstrated that the C-terminus of melittin adopts a helical structure in the complex with LPS, while the Y-terminus appears in an extended conformation. STD experiments permitted to identify those residues of melittin in close proximity with LPS, which appeared to be located at the C-terminus and thus, engaged in the formation of helical structure. 

Utilizing proximate analysis data on all blend constituents and... 

Zirconium presents a particular problem and is a major constituent of at least one crud in a uranium processing circuit. Also, as stated earlier, zirconium will tend to hydrolyze in an HNO3-TBP circuit given the right conditions of shear and of energy input (proximity to saturation of the solvent and the type and construction of contactor, particularly in the coalescing zone). The use of Teflon plates in columns for such an extraction process definitely increased coalescence and decreased the tendency for hydrolysis and crud formation [40]. 

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