Abstract
The optimization of wheat starch esterification (acetylation) with a high degree of substitution was performed through response surface methodology (RSM) via various concentrations of reagents (acetic anhydride), pHs, and temperatures under various ultrasonication frequencies (25, 40, and 25 + 40 kHz). According to RSM methodology, optimized samples were selected by achieving high degrees of substitution at various frequencies, temperatures, and pHs. Solubility, swelling, X‐ray, RVA, DSC, freeze–thaw stability, texture, and SEM analysis of the optimized samples were performed at three frequencies. X‐ray pattern exhibited a more significant reduction in the crystallinity percentage of esterified starch at frequency 25 + 40 kHz compared with 25 kHz, 40 kHz, and native starch. According to DSC analysis, To, Tp, Tc, and enthalpy of gelatinization (ΔH gel) were lower in AC at frequency 25 + 40 kHz compared with AC at frequency 25 and 40 kHz and N starches. According to morphology analysis, in acetylated starches at 25 and 40 kHz, the surfaces and small granules underwent more damage, whereas in 25 + 40 kHz, large granules were more affected than small granules. Upon acetylation, freeze–thaw stability and textural properties of the starch significantly increased and decreased, respectively. The peak and final viscosity of acetylated starch increased (25 + 40 kHz ˃ 25 kHz ˃ 40 kHz ˃ N starch).
Highlights
Starch is an accessible, thickening, and texturizing stabilizer, and of paramount importance when it comes to augmenting the overall quality of the products, reducing costs, and facilitating the processing procedure (Berski et al, 2011; Choi & Kerr, 2003); due to the high affinity toward retrogradation, its application is restricted in certain food products (Kaur, Ariffin, Bhat, & Karim, 2012; Kaur, Sandhu, & Lim, 2010)
According to response surface methodology (RSM) analysis, the optimized Acetylated starch (AC) wheat starch was acetic anhydride (5%), pH 8.5, and temperature 60°C with 1.22%, 1.37%, and 1.02% acetylation for 25 kHz, 25 + 40 kHz, and 40 kHz, respectively
The results showed that the X‐ray pattern of wheat starch was the same as other cereals (A pattern)
Summary
The weakened internal bond structure in the starch granules, due to the derivatized modifier groups, enhances the freeze–thaw stability, reduces the gelatinization temperature, generates high levels of peak viscosity, and leads to starch paste clarity (Han, 2010; Han, Lee, Lim, & Lim, 2005). There is no information about the acetylation of starch under various frequencies of ultrasonication. The aim of this study was to optimize the AC wheat starch in various parameters such as acetic anhydride concentration, pH, and temperature under frequencies (25, 40, and 25 + 40 kHz) of bath ultrasound; the optimization was further investigated on the amount of modification (molar substitution) in the modified starch. VB and VS are the volumes of the control and modified samples (0.2 M HCl basis), respectively.
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