Phosphate starch esters

Starches have been chemically modified to improve their solution and gelling characteristics for food applications. Common modifications involve the cross linking of the starch chains, formation of esters and ethers, and partial depolymerization. Chemical modifications that have been approved in the United States for food use, involve esterification with acetic anhydride, succinic anhydride, mixed acid anhydrides of acetic and adipic acids, and 1-octenylsuccinic anhydride to give low degrees of substitution (d.s.), such as 0.09 [31]. Phosphate starch esters have been prepared by reaction with phosphorus oxychloride, sodium trimetaphosphate, and sodium tripolyphosphate the maximum phosphate d.s. permitted in the US is 0.002. Starch ethers, approved for food use, have been prepared by reaction with propylene oxide to give hydroxypropyl derivatives [31]. 

Potato starch contains 0.07 to 0.09% phosphate mono-ester groups.53 This native monosubstitution makes the starch anionic and sensitive to the presence of other ions. Similarly, the US Code of Federal Regulations allows up to 0.4% phosphate... 

It appears that phosphorus is related to the formation of starch in the plant. Thus Hanes has synthesized a linear polysaccharide from a-D-glucopyranosc 1-phosphate (Cori ester) through the action of potato phosphorylase. Dunlap and Beckmann and likewise Cori have found that the B-fraction activates this enzymic synthesis, while the A-frac-tion is inactive. It has not been established whether this effect is due to the branched character of the B-fraction or to the presence of phosphate in its structure. 

Mixed carbonic anhydrides, acyl guanidine, N-acylimidazoles, N-acyl-N -methylimidazolium chloride and acyl phosphates are other agents that have been used to esterify starch in water [65-76]. Starch esters containing carboxylic acid group have been prepared by reaction with cyclic dibasic anhydrides [65]. 

Typical a. are - carboxymethyl starch (- starch ethers), starch adipate, starch citrate, starch mal-eate, starch phosphate, starch succinate, starch sulfate, starch xanthate (->starch esters), - oxidized starches. 

If water is eliminated from the reaction mixture, the equilibrium tends to the right side, and almost all acid or alcohol is transferred to the ester. In context with RR, the following esters should be mentioned - Cellulose esters, - starch esters, - sucrose fatty acid esters, - soibitan esters of fatty acids, - sulfosuccinates, - fatty acid esters, - waxes, fats and oils and all other glycerides, alkyd resins, esters of inorganic acids with fatty alcohols, e.g., fatty alcohol sulfates, fatty alcohol ether sulfates, fatty alcohol phosphates, phtalates, azelates and sebacates (aplastic additives), as well as the esters of - citric acid, - tartaric acid and - lactic acid. 

Potato starch is the only one in which inorganic phosphate exists as a natural - starch ester. Other phosphate is found as organic, solvent-extractable phospholipid, in part complexed by the an lose moiety of the starch granule, especially in starches of the triticeae group. 

Compared to native starches, monophosphate esters have a decreased gelatinization temperature range and swell in cold water at a DS of 0.07. Starch phosphates have increased paste viscosity and clarity and decreased retrogradation. Their properties are in many ways similar to those of potato starch, which naturally contains phosphate groups. 

The first step in glycolysis is the phosphorylation of glucose to give the ester glucose 6-phosphate. The glucose starting material may well have come from hydrolysis of starch obtained in the diet, or by utilization of glycogen reserves. 

Most native starch types are slightly phosphorylated with phosphate groups monoesterified to the glucose residues (Blennow et ak, 2002). The presence of phosphate esters in starch has been known for more than a century (Fembach, 1904). The content of phosphate esters in starch... 

Potato starch, and tuberous starch in general, has some unique properties as compared to cereal starches. The most important ones include long amylopectin chains forming hydrated and ordered B-type crystallites and the presence of phosphate esters. The clusters of potato amylopectin are comparatively small, comprising 5-10 short chains. The internal part ofthe clusters is organized into branched building blocks mainly found in the amorphous lamellae of the... 

Muhrbeck, R, Eliasson, A. -C. (1991). Influence of the naturally-occurring phosphate-esters on the crystallinity of potato starch. J. Sci. Food Agric., 55, 13-18. 

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