The kinetics of the acetylation of gelatinised potato starch

Abstract

The reaction rates, in the base-catalysed acetylation of gelatinised aqueous starch (4 wt%), by vinylacetate (ViAc), were investigated in a semibatch reactor at temperatures ranging from 20 to 50°C. The desired starch acetylation reaction is accompanied by an undesired parallel base-catalysed hydrolysis reaction of vinylacetate and a consecutive hydrolysis reaction of the acetylated starch. The rate equations are: Starch acetylation: &AC =-k, cvic CRO-Starch acetate hydrolysis: &A= =-kz CRAM con-Vinylacetate hydrolysis: &tic =-k3 CViAc COW where k1,2,3 = k1,2,3, cHIO, CViAc is the vinylacetate concentration, cRo-is the concentration of the dissociated starch hydroxyl group, cRAc is the concentration of acetylated starch and con-is the sodium hydroxide concentration; k is the reaction rate constant. The temperature dependency of the rate constants was measured as: Acetylation of starch: Deacetylation of the starch ester: Hydrolysis of vinylacetate: where R (gas constant) = 121.8 J/mol"C.

Mass Transfer and Chemical Reaction Approach of the Kinetics of the Acetylation of Gadung Flour using Glacial Acetic Acid

“…Kinetic data on the acetylation of potato starch in a slurry system had been reported by Jetten et al [7] and the rates of the acetylation reactions of potato starch using vinil acetate had been reported by de Graaf et al [3]. However, no data have been published on the rates of the acetylation reactions of gadung flour (GF) with glacial acetic acid (GAA).…”

“…Thus, the rate of acetic acid decomposition: (4) From previous studies of the acetylation of potato starch with vinyl acetate, de Graaf et al [3] reported that acetylation reaction was first order both in starch and acetyl. …”

“…(8) From previous studies, starch acetate hydrolysis reaction is known to be first-order in both RAc and OH - [3], thus: (9) in this study, the concentration of water (CH2O) are in excess, so the changes in its concentration are negligible, thus Equation (9) becomes: (10) based on stoichiometric equations, Equation (10) may be written as: (11) The forward reaction rate (starch acetate formation) is a function of CAg and CAl , and the reverse reaction rate (starch acetate hydrolysis) is a function of CRAc and water. The overall reaction rate of starch acetylation hydrolysis are given by:…”

“…Acetylated starches are used in a large variety of foods manufacturing including baked, canned pie fillings, sauces, retorted soups, frozen foods, baby foods, salad dressings, and snack foods [2]. Acetylated starches with degree of substitution (DS) between 0.01-0.2 are approved by the FDA for used as food materials [3]. Their usage is based on properties with respect to film forming, binding, adhesivity, thickening, stabilizing and texturing.…”

The kinetics of the homogeneous benzylation of potato starch in aqueous solutions

“…Modified starches are used in numerous applications and industrial processes (de Graaf, Broekroelofs, Janssen, & Beenackers, 1995). One of these applications is the use of benzylated starch as paper finisher (Wurtzburg, 1986).…”