61A-37 |
Calorimetic analysis of starch gelatinization in water-ethanol mixtures |
R. V. POTINENI, J. N. Coupland, D. B. Thompson, and K. Seetharaman. Department of Food Science, Pennsylvania State University, 111, Borland Lab, University Park, PA 16802 Starch gelatinization temperatures have been found to increase with increasing concentration of sugars. However, the effects of other materials such as ethanol on starch gelatinization have not been well studied. The objective of this study was to investigate the effects of ethanol concentration on the thermal behavior of common corn-starch using DSC. Ethanol-water mixtures were made at concentrations of 0%, 25%, 50%, 75%, and 100% v/v of ethanol in water. Pre mixed solvent was added to starch (~ 15 mg) to make ~30% (w/w) starch suspensions. Samples were heated in a DSC from 20°C to165°C at a heating rate of 5°C/min. Gelatinization onset (To), and peak (Tp) temperatures were calculated. Controls for 25%, 50%, 75% and 100% ethanol suspensions were made by adding only the calculated percentage of water. Microscopy of these starches was done using crossed polarizers. The To for control samples at different moisture contents was in the same range (61-62°C), while the gelatinization range broadened as the water content decreased. The gelatinization and amylose-lipid complex peaks overlapped as the water content in the control sample decreased. In ethanol-containing samples, the To and Tp for gelatinization shifted to higher temperatures compared to the respective controls. In samples with 50% ethanol, an exothermic event was observed at about 92°C, following and possibly confounded with the gelatinization endotherm. A dual endothermic peak was also observed at 118°C and 138°C in 50% and 75% ethanol samples. Microscopic analyses show a lower fraction of swollen starch as the ethanol fraction increased. Added ethanol had a different effect on the starch gelatinization than has been previously reported for sugars. Ethanol added to water apparently affects both starch gelatinization and dissociation of starch-lipid complexes.
Session 61A, Carbohydrate
|