title: A mechanistic approach to studies of the possible digestion of retrograded starch by α-amylase revealed using a log of slope (LOS) plot.
abstract: The rate and extent of digestibility of starch were analysed using the logarithm of the slope (LOS) method. Digestibility curves with α-amylase were obtained for starches in their native, gelatinised and 24h retrograded form. A LOS plot of the digestibility curves was then constructed, which allowed the rate constant (k) and the concentration of the product at the end of the reaction (C∞) to be calculated. It also allowed the identification of rapid and slow phases in starch digestion. Upon gelatinisation, both k and C∞ increased with dramatic changes notably in C∞; however after starch samples had been stored for 24h at room temperature, k was not affected but C∞ decreased. This suggests that retrograded starch is virtually inert to amylase action. Both k and C∞ were strongly related to the increase in degree of order of the α-glucan chains, monitored by FTIR-ATR spectroscopy, in retrograded starch.
authors.affiliation: King's College London, School of Medicine, Diabetes and Nutritional Sciences Division, Biopolymers Group, Franklin-Wilkins Building, 150, Stamford Street, London SE1 9NH, UK.
authors.forename: Hamung
authors.initials: H
authors.lastname: Patel
authors.affiliation: King's College London, School of Medicine, Diabetes and Nutritional Sciences Division, Biopolymers Group, Franklin-Wilkins Building, 150, Stamford Street, London SE1 9NH, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Day
authors.affiliation: King's College London, School of Medicine, Diabetes and Nutritional Sciences Division, Biopolymers Group, Franklin-Wilkins Building, 150, Stamford Street, London SE1 9NH, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Butterworth
authors.affiliation: King's College London, School of Medicine, Diabetes and Nutritional Sciences Division, Biopolymers Group, Franklin-Wilkins Building, 150, Stamford Street, London SE1 9NH, UK. Electronic address: peter.ellis@kcl.ac.uk.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Ellis
mesh_terms: D016014:Linear Models; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013213:Starch / Q000737:chemistry / Q000378:metabolism*; D000516:alpha-Amylases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D013213:Starch; D000516:alpha-Amylases
keywords: FTIR-ATR; First-order kinetics; Log of slope plot; Retrogradation; Starch; α-Amylase