THE REACTIVITY OF NATIVE AND AUTOCLAVED STARCHES FROM DIFFERENT ORIGINS TOWARDS ACETYLATION AND CATIONIZATION

Native potato, waxy corn, corn, wheat, field pea and lentil starches w ere autoclaved at 15 psi, 121 degrees C for 1 min. Scanning electron m icrographs of the native and autoclaved starches showed no changes in granular surfaces and shapes. In arl starches, the X-ray intensities a t most of the d-spacings between 3-18 Angstrom increased upon autoclav ing, being more pronounced in potato. The X-ray patterns of cereals an d legumes remained unchanged, while that of tuber (potato) became more cereal-like. Differential scanning calorimetry of the starch samples revealed that autoclaving increased the gelatinization transition temp eratures of wheat but decreased that of potato, the changes observed i n waxy corn, corn, field pea and lentil starches were very small. The gelatinization enthalpy of all native starches decreased upon autoclav ing while the percentage decrease was highly marked in potato. Image a nalysis of the native and autoclaved starches revealed changes in the granule size distribution patterns. Also, the population mean area of all native starch granules considerably increased upon autoclaving. Ac etyl binding capacity, measured at 5% and 10% acetic anhydride additio n levels, was higher in autoclaved than in native starches. Furthermor e, autoclaving had no influence on starch cationization, studied at 3% and 6% reagent addition levels. The results indicated that the change s in starch molecular organization caused by autoclaving enhanced its reactivity towards acetylation but not cationization.