ABSTRACT
Male Wistar rats were fed on a conventional diet containing normal corn starch or 6% enzyme-resistant starch originating from either raw or retrograded high-amylose corn starch. Furthermore, the diets were either cholesterol-free or contained 1% cholesterol and 0.1% cholic acid. The main objective of this study was to investigate whether the addition of enzyme-resistant starch to a rat conventional diet had any effect on cholesterol metabolism. Therefore, plasma and liver cholesterol concentrations, plasma HDL:LDL cholesterol ratios and neutral steroid and bile acid excretion were determined. No significant effect of enzyme-resistant starch feeding on plasma and liver cholesterol concentrations was found. However, consumption of raw or retrograded high-amylose corn starch resulted in a decrease in esterified and total liver cholesterol concentrations of 24 and 22%, respectively. This was accompanied by a reduction in plasma esterified and total cholesterol levels of 4% and a tendency to higher daily faecal coprostanol and total bile acid excretion.
Subject(s)
Animal Feed , Cholesterol/metabolism , Liver/metabolism , Starch/administration & dosage , Amylose , Animals , Bile Acids and Salts/analysis , Cholestanol/analysis , Cholesterol/administration & dosage , Cholesterol/blood , Feces/chemistry , Male , Rats , Rats, Wistar , Zea maysABSTRACT
In view of a possible application of the alpha-amylase from Bacillus licheniformis as a time-temperature integrator for evaluation of heat processes,(11) thermal inactivation kinetics of the dissolved and covalently immobilized enzyme were studied in the temperature range 90-108 degrees C. The D-values (95 degrees C) for inactivation of alpha-amylase, dissolved in tris-HCl buffer, ranged from 6 to 157 min, depending on pH, ionic strength, and Ca(2+) and enzyme concentration. The z-value fluctuated between 6.2 and 7.6 degrees C. On immobilization of the alpha-amylase by covalent coupling with glutaraldehyde to porous glass beads, the thermoinactivation kinetics became biphasic under certain circumstances. For immobilized enzyme, the D-values (95 degrees C) ranged between 17 and 620 min, depending largely on certain environmental conditions. The z-value fluctuated between 8.1 and 12.9 degrees C. In each case of biphasic inactivation, the z-value of the stable fraction (with the higher D-values) was lower than the z-value of the labile fraction.
