Characterization of chemically modified corn starches

OLIVIA V. LÓPEZ; MARÍA ALEJANDRA GARCÍA; NOEMÍ E. ZARITZKY

Iguassu Falls City

Conferencia; International Conference of Agricultural Engineering-XXXVII Brazilian Congress of Agricultural Engineering-ASABE ILES VIII; 2008

Brazilian Association of Agricultural Engineering-International Commision of Agricultural Engineering-American Society of Agricultural and Biological Engineers

The aim of this work is to study the physicochemical, morphological, thermal and rheological properties of different chemically modified corn starches in comparison to the native corn starch ones. Substituted, dual modified (substituted and cross-linked) and acid modified corn starches were analyzed. Chemical modifications did not cause any change in the morphological properties of starch granules. The substitution and dual modification reduced significantly amylose concentration. Molar substitution degree values were in agreement with the permitted limits. All starch granules exhibited a typical cereal X ray diffraction pattern with a lower crystallinity degree than native starch. Substitution and dual modification decreased thermal parameters of gelatinization (onset temperature, To; peak temperature, Tp and enthalpy, ÄH). For acid modified starch To and Tp did not differ from those of the native starch, while a higher value was obtained for ÄH. With regard to the rheological analysis, acid modified starch showed a Newtonian behavior while substituted and dual modified starches exhibited a viscoelastic response.