Acetylation and characterization of the barley starch

Abstract

The starch is constituted for amylase and amilopectyn. The acetylation is a chemical modification for estherification, in which his hydroxyl groups are replaced with acetyl groups that offer to him major stability, changing the physicochemical and functional properties of the starches. The acetyl starches presents 6-10ºC less in the gelatinization temperature (Tg) and the peak of maximum viscosity is major with regard to the native one, which indicates that the acetyl starches disperse easier. The acetylation also increases the clarity and stability of the gels and reduces the retrogradation. To isolate the starch of barley, to modify the same ones by means of chemical agents (anhydride acetic, AA and acetate of vinyl, AV) and to characterize them, they have been aims of this work. With regard to the content of present starch in the grain (60%) the obtained performance was 50 %. The percentage of acetyls reached between 3 and 6%; with the use of the AA, 1.6 times were obtained major incorporation of acetyl groups; the degree of substitution was of 0.143 and 0.240, as AV or AA was in use, respectively. A difference was observed in the average diameter of particle between three starches, for the native starch (AN) it was of 19μm, whereas for the starches treated with AV and AA it was of 22μm and 104μm respectively. The increase in the size owes to the introduction of the acetyl groups to the chains of starch. The diffraction of X-rays allowed to observe that the peak of crystallinitty of the starch treated with AV is great more defined in comparison with the AN, presenting a crystallinitty of 28.3 %, for the starch modified with AA it diminishes his peak of crystallinitty and his crystallinitty is 28 %, this loss in the crystallinitty owes to that the modification was carried out in the crystalline region of the starch. The morphology of the granule did not fall ill for the process of acetylation. FTIR analysis corroborated the degree of acetylation of the starch. One concludes that the barley starch can be modified by acetylation with VA and these can be used in the nourishing industry like additives, since they are within the rank allowed by the FDA.