Physicochemical properties of waxy and normal corn starches treated in different anhydrous alcohols with hydrochloric acid

Corn starches (25 g, d. b.) were treated in anhydrous methanol, ethanol, 2-propanol or 1-butanol (100 ml) with 1 ml 36% hydrochloric acid at 45 °C for 1 h, the molecular weight and chain length distributions of starch were examined by high-performance size-exclusion chromatography (HPSEC), and the granule size, granular structure, λmax, blue value, solubility and gelatinization thermal properties of starch were also examined. Results showed the recovery yields of the treated starch were higher than 96%, and the granule sizes of treated starches were slightly lower than their counterpart native starch. Starches after acid-alcohol treated showed internal fissures or cavities in some granules, and the number of granule with fissures or cavities increased with the increasing carbon number of alcohol. The weight average degree of polymerization and relative content of F1 fraction of starch after treated profoundly decreased, and the amylose and long chain of amylopectin of starch were preferentially degraded. The degradation extent of molecules after acid-alcohol treatment was found directly related to the alternation of internal structure of starch granule. The λmax and blue value of both waxy and normal corn starches after treated also obviously decreased with the increasing carbon number of alcohol, while the solubility of starch profoundly increased after treated. The gelatinization onset temperature (To) of acid-alcohol treated waxy corn starch decreased with the increasing carbon number of alcohol, but the treated normal corn starches showed similar To values. Despite the alcohol used, the solubility of treated waxy corn starch linearly correlated (r2=0.983) with T/To value (T was the measuring temperature used for solubility determination). Whereas, normal corn starch treated in different alcohols showed distinct relations between T/To and solubility.