Starch phosphorus content

Overall, the large number of significant differences among the fractions of all three bean types, reveals that the various minerals studied were not equally distributed among the fractions, except for sodium, but rather that partitioning occurred. Consistent with the ash values obtained, the protein flour fractions of the three bean types contained larger amounts of Fe, Mg, P, Z, and K whereas the starch II fractions contained smaller amounts of these minerals and Ca and Cu than the other flour fractions. Phytic acid content ranged from 8.7-30.2 mg/g for navy flours, from 4.3-23.7 mg/g for pinto flours. Total phosphorus content correlated well with both phytic acid content and protein content. Phytic acid content was... 

Most potato starches are composed of a mixture of two polysaccharides, a linear fraction, amylose, and a highly branched fraction, amylopectin. The content of amylose is between 15 and 25% for most starches. The ratio of amylose to amylopectin varies from one starch to another. The two polysaccharides are homoglucans with only two types of chain linkage, a-(l 4) in the main chain and a-(l 6)-linked branch chains. Physicochemical properties of potato and its starch are believed to be influenced by amylose and amylopectin content, molecular weight, and molecular weight distribution, chain length and its distribution, and phosphorus content (Jane and Chen, 1992). 

The phosphorus content can be determined by wet oxidation of the starch with sulfuric (or nitric) acid and hydrogen peroxide followed by colorimetric estimation of the phosphomolybdate complex. A detailed procedure for gravimetric determination can be found in AACC method 40-57 (AACC, 2000). However, large sample sizes (2-5 g) are required in this method. 

Phosphorus Content in Starch Phosphates and Degree of Substitution with Phosphoric Acid Moieties22... 

Starch-P4O,0 (Reaction mixture) Phosphorus content Reaction conditions Number of phosphorus moieties on I glucose unit... 

Generally, the phosphorus content in starches is associated with different pasting properties, and it confers a larger ion binding capacity. In wheat and com starch, phosphorus is present largely or wholly as adsorbed phos-phatides (extractable with boiling 85% methanol) associated preferentially with the amylose fraction. 

Phosphorus content of potato starch (Geddes et al, 1965) varies during development of the tubers it increases from being undetectable in the amylose of tubers of 1-cm diameter, to 0.005% in tubers 8 to 9 cm in diameter, and, in amylopectin, from 0.029% in the 1-cm diameter to 0.049% in the largest (8- to 9-cm tubers). 

Anionic dyes readily adsorb on starch (Tables XXXIX-XLIII).802 However, there is evidence that this rule is violated in the case of potato starch.802-803 The simplest intepretation of this fact has been presented in terms of the phosphate groups present in potato starch. A relationship exists between the phosphorus content in potato starch and the sorption capacity of that starch for Methylene Blue. The sorption follows the Langmuir isotherm. Extrapolation of the result to 0% phosphate leads to the conclusion that no Methylene Blue would be adsorbed on phosphate-free starch.804 Methylene Blue is better adsorbed on potato starch, but is also... 

As some fractions of the limit dextrins produced by the common amylases have a much higher phosphorus content than starch, the author assumed that the substitution with phosphoric acid is one of the anomalies postulated as the cause of the limit dextrin formation. That the phosphoric acid acts in this way is evident from the investigations of Posternak, who isolated a tetraose phosphate from a mixture of limit dextrins. On acid hydrolysis this gave D-glucose 6-phosphate. 

The phosphoric acid is not evenly distributed over the whole starch substance amylose is free or almost free from phosphorus.It may be mentioned that amylose prepared according to Ling is reported to have a very low phosphorus content. The author has obtained such preparations in some cases, but for the most part preparations were obtained which had the same or a higher phosphorus content than the starch. These preparations were not completely saccharified by /3-amylase and obviously contained amylopectin even if the solutions had a low viscosity. 

Most amylases have only a slight action on the phosphate groups. As mentioned before, the 3-dextrin from potato starch contains all the phosphorus of the starch. This is in accordance with the fact that the phosphorus is concentrated in the amylopectin. A /3-dextrin from arrow-root starch had a phosphorus content of 0.051 % while the starch itself had 0.019%. Since the /3-dextrin corresponds to 40% of the starch, it is evident that here also all the phosphorus is left in the /3-dextrin. 

Even if a strong secondary conversion of the dextrins has occurred and the total yield of limit dextrins is low, these dextrins will contain a great deal of the phosphorus content of the original starch. This is demonstrated by the data of Table XVIII. 

Samec and coworkers have differentiated between the fractions on the basis of phosphorus content. Undoubtedly, organic phosphate is associated primarily with the B-fraction of potato starch, contributing polarity to that component. In the case of corn starch, the distinction is not as sharp, since the total phosphorus content is very much lower. Also, it is possible to separate the B-fraction of corn starch into subfractions of high and low phosphorus content, and these do not differ materially in. solubility behavior or alkali lability. Thus phosphorus is believed to constitute only a minor difference between the fractions. 

Of the esters, starch phosphate is produced by reaction with phosphorus oxychloride, polyphosphates, or metaphosphates a cross-bonded product results. Total degree of substitution is determined by measuring the phosphorus content, and the mono- to disubstitution ratio can be calculated by potentio-metric titration. Allowance is made for the natural phosphorus content of the starch. Treatment of starch with acetic anhydride produces starch acetate, which has improved paste stability over native starch. The acetyl group is very labile, and hydrolyses readily under mild alkaline conditions. When a known amount of alkali is used, the excess can be titrated and the ester function measured. This is not specific, however, and a method based on an enzymatic measurement of the acetate has been developed in an ISO work group. The modified starch is hydrolyzed under acidic conditions, which releases acetic acid and permits filtration of the resulting solution. Acetic acid is then measured by a commercially available enzyme test kit. Both bound and free acetyl groups can be measured, and the method is applicable... 

Potatoes are a poor source of minerals, except for the abundant element potassium the calcium content is particularly low. The phosphorus content is rather higher, since this element is an integral part of the potato starch molecule, but some 20 per cent of it is in the form of phytates (see p. 115). 

Swinkels29 collected published characterization data for tapioca starch and compared it to that for other starches of commercial significance (Table 12.4). Tapioca starch is differentiated from other starches by its low level of residual materials (fat, protein, ash), lower amylose content than for other amylose-containing starches, and high molecular weights of amylose and amylopectin. The small amount of phosphorus in tapioca starch is partially removable30 and, therefore, not bound as the phosphate ester as in potato starch. It is also common to find protein and lipid values of zero, as reported by Hicks.31 The very low protein and lipid content is an important factor which differentiates tapioca starch from the cereal starches. 

To explain the variation in the phosphate content of starches, it is postulated that some plants contain a specific phosphatase such an enzyme would have to possess unusual powers of penetration, since R-en-zyme, for example, cannot attack the interior of an amylopectin molecule. Moreover, a considerable proportion of the phosphorus would be situated in outer chains there is no evidence for this. (5) The formation of waxy-type starches is attributed to a low activity of the debranching enzyme caused by the presence of an inhibitor(s) to the debranching mechanism or by a deficiency of the debranching enzyme. Waxy-type starches should, therefore, contain a higher degree of branching than that actually observed (about 5%). 

Phosphoras structures and contents in starches vary with the botanical source, maturity and growing conditions of the plant. Most normal cereal starches contain phosphorus in the form of phospholipids, whereas phosphorus in root and tuber starches is in the form of starch phosphate monoesters [2],... 

---