title: Does viscosity or structure govern the rate at which starch granules are digested?
abstract: The rates of in vitro digestion of incompletely or fully gelatinised potato and corn starch were measured at 37 °C over 20 min in a rheometer fitted with cup and vane geometry at shear rates of 0.1, 1 and 10 s(-1). Shear rate did not influence the rate of starch digestion provided it was close to physiological levels. However, rates of digestion were significantly reduced when shear rates were below the physiological range (0.1 s(-1)) or when gelatinisation was incomplete. At physiological shear rates the relationship between starch digestion and viscosity was sigmoid in form and following a short initial slow phase a rapid decline in viscosity occurred as starch was digested and the structural integrity of the granules was lost. Conversely, when shear rate was reduced below physiological levels or gelatinisation was incomplete, digestion was hindered, granule integrity was maintained and the relationship between starch and viscosity became linear.
authors.affiliation: Institute of Food, Nutrition and Human Health, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand; Riddet Institute, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand. Electronic address: ahardacre@massey.ac.nz.
authors.forename: Allan K
authors.initials: AK
authors.lastname: Hardacre
authors.affiliation: Institute of Food, Nutrition and Human Health, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand; Riddet Institute, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand.
authors.forename: Roger G
authors.initials: RG
authors.lastname: Lentle
authors.affiliation: Institute of Food, Nutrition and Human Health, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand.
authors.forename: Sia-Yen
authors.initials: SY
authors.lastname: Yap
authors.affiliation: Riddet Institute, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand; Plant and Food Research, Private Bag 11600, Palmerston North 4442, New Zealand.
authors.forename: John A
authors.initials: JA
authors.lastname: Monro
mesh_terms: D000468:Alkalies / Q000737:chemistry; D000681:Amylases / Q000737:chemistry* / Q000378:metabolism; D004063:Digestion; D005782:Gels / Q000737:chemistry; D006868:Hydrolysis; D013213:Starch / Q000737:chemistry* / Q000378:metabolism; D014783:Viscosity
chemical_list: D000468:Alkalies; D005782:Gels; D013213:Starch; D000681:Amylases
keywords: Amylolysis; Gelatinisation; Rheology; Shear rate; Starch digestion