Starch esterified

The DS has a strong influence on the hydrophobic character of the modified starches and, as expected, increasing the DS decreases the polarity of the surface. For DS > 0.1, contact angles are greater than 90° with quite a low total surface energy, indicating a significant hydrophobicity of the material and a low wettability as previously reported for esterified starches [74-76]. 

Acetic anhydride and sulfuric acid together also form a powerful acetylating mixture capable of esterifying starch at low temperatures. Pregl treated a Zulkowsky heat-modified potato starch with a mixture of cold acetic anhydride and sulfuric acid. After 40 hours, most of the starch dissolved to produce a product containing 46.7-47.4% acetyl. 

Conventional synthesis of such materials employs fiitty-acid chlorides or anhydrides in organic solvents. Recently, a fiee-solvent method to esterify starch was developed in our laboratory using formic acid and octanoyl chloride as the gelatinizing and acylating agents respectively. After optimization of reaction conditions, starch octanoate with DS of 1.7 was obtained with a recuperation yield of 89 %. ... 

Properties of starch esters depend on the type of an esterifying agent applied, conditions of the reaction, and a DS. The esterified starches have found applications in the food industry, papermaking industry, in pharmacy, and have been used for the production of thickening agents and for permanent finishing of fabrics [57],... 

The effects of various surfactants on the properties of starch-based nanocomposites have also been studied and most of the smdies point to their positive effects on mechanical properties of nanocomposites. For example, glyceryl monostearate (GMS) was used by Mondragon et al. (2008) in MFC/TPS, which resulted in improvement in mechanical properties. Similar improvements in properties were reported by Takagi and Asano (2008a, b) for CNC/esterified starch nanocomposites. 

In addition, esterified starch has an improved freeze-thaw stability. These starches are utilized as thickeners and stabilizers in bakery products, soup powders, sauces, puddings, refrigerated food, heat-sterilized canned food and in margarines. The starch esters are also suitable as protective coatings, e. g., for dehydrated fruits or for aroma trapping or encapsulation (cf. Table 4.26). 

Our objective was to prepare more hydrophobic starches to incorporate them in latex preparation for decorative paints so that substrates derived from fossil fuel can be replaced by modified starches derived from renewable resources. Partial substitution of starch with acetate, hydroxypropyl, alkylsiliconate or fatty-acid ester groups was described in the literature for the synthesis of more hydrophobic starch. An alternative route was employed consisting of grafting octadienyl chains by butadiene telomerization (8,9). This reaction (Figure 4) was catalyzed by hydrosoluble palladium-catalytic systems prepared from palladium diacetate and trisodium tris(m-sulfonatophenyOphosphine (TPPTS). Starch octadienyl ethers are expected to be much less sensitive towards hydrolysis compared to the esterified starches. 

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]. 

Esterified starches are produced from acetate, phosphate, or succinates. Acetylated starches are manufactured from anhydrous acetic oxide in a slightly alkaline (pH 8-8.4 due to NaOH addition) starch slurry. The anhydrous acetic oxide reacts with hydroxyl groups, forming methyl esters. The main functional modification of acetylated starches is the lower gelatinization and peak-viscosity temperatures that usually occur at approximately 10°C, compared to native raw counterparts. In addition. 

In many appHcations succinic acid and anhydride are esterified with polyhydric compounds, ie, polyols (57—59), cellulose (60), or starch (61—64). 

Starches can be esterified by modifications with an acid. An ester is the result of reacting an alcohol with an acid. The starch loses a hydroxyl group, and the acid loses a hydrogen. These combine to form water as the other product of the reaction. 

Formic acid appears to show some selectivity in preferentially esterifying primary hydroxyl groups. Traquair161 describes the preparation of unstable starch formates. The monoformate is believed to be esterified at position 6. The periodate oxidation of monoformates of starch and limit dextrin indicates that ester linkage is predominantly... 

Interaction of solvent with sugars being separated is typified by the lactone-uronic acid interconversion which may take place during chromatography in collidine mixtures.27 Moore and Stein have shown that acidic amino acids, in an acidic 1-butanol solvent on starch columns, are esterified to the extent of 6 to 7 % during chromatography.63... 

Hydrophobic starches are another new class of starches for use on the size press. Some grades are based on waxy starches and are esterified. Hydrophobic starches provide improvements in water, ink and solvent holdout, as well as decreased sheet porosity. 

Starches esterified with octenylsuccinic anhydride are also monosubstituted, but are primarily produced not for stabilization, but because they have hydrophobic... 

Specifically, D-glucose < maltose < maltotriose < amylose < starch < amylo-pectin < cellulose (Greenwood, 1967). Trends indicated are that thermochemical stability increases with the DP, branching, and 1,4-fi bonding. Chemical bonds other than 1,4-a and 1,4-(3 introduce heat and acid instability. Either of these two bonds is less easily depolymerized when the sixth pyranose carbon is oxidized to the carboxyl group rather than esterified for this reason, low-methoxyl pectin is more stable than high-methoxyl pectin. 

Starches contain phosphorus, nitrogen, and very low amounts of other minerals. In the cereals, most of the phosphorus is in the form of phospholipids, whereas in potato starch the phosphorus is esterified to certain glucose residues in the polysaccharide. 

There are also patents on compositions of starch with modified esterified, etherified, and cross-linked starch to produce sizes1061 and adhesives.1062-1064... 

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