Structural characteristics and gelatinization properties of sour cassava starch
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Sour cassava starch is considered a modified starch used in many countries in several food products. Understanding modified starch granule structure is important in the knowledge of its physicochemical properties. Differential scanning calorimetry has been used to evaluate the effect of modifications on gelatinization of several starches. The aim of this work was to evaluate the structural characteristics and the gelatinization properties of commercial sour cassava starches with different total titratable acidity values, and to propose a new sour cassava starch classification by principal component analysis. Total titratable acidity of cassava starches varied from 2.16 to 6.74 %, which classified almost all samples as sour cassava starch. The sour cassava starches of classes from 1 to 4 showed low in iodine affinity and consequentially in apparent amylose content. Cassava starches with acidity ranging from 2.64 to 4.92 % (classes 1-4) displayed erosions on granule surface, high relative crystallinity, and high temperature and enthalpy gelatinization. Cassava starches with acidity above 4.99 % (classes 5 and 6) showed deeper erosions on granules, lower relative crystallinity and enthalpy, which indicated the beginning of degradation of the granule crystalline areas. Principal component analysis allowed verifying that the number of total titratable acidity classes could be reduced from 6 to 3, represented by groups with similar samples in relation to the structural and physicochemical behavior.