Synthesis and Characterization of Starch Acetates with High Substitution

Abstract

Cereal Chem. 81(6):735-740Acetylation of high-amylose (70%) maize starch to high degree of substitution (DS) was studied by reacting starch with acetic anhydride using 50% aqueous NaOH as the catalyst. DS increased with increasing reaction times and increasing ratios of acetic anhydride to starch. Reaction efficiency (RE) increased with longer reaction times and decreased with increases in the ratios of acetic anhydride to starch for extended reaction times. Increasing the amount of NaOH increased both DS and RE. A series of starch acetates with DS values of 0.57-2.23 were prepared and their crystalline structures, chemical structures, thermal stability, and morphological properties were investigated. After acetylation, and as DS increased from 0.57 to 2.23, the crystalline structures of starch steadily disappeared. The carbonyl group's peak at 1,740 cm -1 appeared in the FTIR spectra. The intensity of this peak increased with a decrease in the peak intensity of the hydroxyl groups at 3,000-3,600 cm -1 , indicating that the hydroxyl groups on starch were replaced by the acetyl groups. Thermal stability of starch acetates increased. The smooth surface of the starch granules became rough with acetylation. Further acetylation led to the loss of the starch granules and the formation of beehive-and fibrouslike structures.

Acetylation of banana (Musa paradisiaca L.) and maize (Zea mays L.) starches using a microwave heating procedure and iodine as catalyst: Partial characterization

“…An extremely broad band due to hydrogen bonded hydroxyl groups appeared at 3421 cm À1 [15]. Compared to native starches, starch acetates had a strong absorption band at 1740 cm À1 assigned to the stretching of the ester carbonyl C --O and indicated the acetylation of starch [29]. These new band suggest that the acetylated starch products were formed during the esterification process.…”

EVALUATION OF THE COAGULANT CAPACITY OF STARCH OBTAINED FROM TOPOCHO PELIPITA PLANTAIN CLONE (Musa ABB) FOR TURBIDITY AND COLOR REMOVAL IN RAW WATERS

“…In a similar way, DS increased from 0.8 ± 0.02 to 1.22 ± 0.03 in the LAS and HAS samples, respectively. This difference was caused by the volume of acetic anhydride that was added during the modification process, which led to a higher number of acetyl groups to be introduced into the starch molecule (Xu et al 2004, Sánchez-Rivera et al 2010). …”

“…Figure 1 shows the presence of peaks at wavelengths that are related to the main chemical groups commonly found within the native and acetylated starch molecules (Mano et al 2003, Xu et al 2004 , which are related to stretching of chemical groups within the anhydroglucose unit of the starch molecule (Xu et al 2004), such as-OH, -CH, CO-H bending, -CO stretching, and C-O-C bending, respectively (Stuart 2004). Figure 2 shows the SEM micrography that was taken for native starch (NS), low acetylated starch (LAS) and high acetylated starch (HAS).…”

“…Among them, starch emerges as a good candidate, because it comes from agricultural sources and it can be produced at low cost (Muhammad et al 2015, Ramavandi 2015. The polar nature of starch allows its dispersion in aqueous media, but to achieve a complete dissolution, it is necessary the addition of an alkali compound or a heat treatment, which restrict its application in CF water treatment (Xu et al 2004, Pal et al 2005, Sableviciene et al 2005. Chemical modification, such as acetylation, arises as an excellent alternative to improve its properties as a coagulant (Xu et al 2004).…”

“…The polar nature of starch allows its dispersion in aqueous media, but to achieve a complete dissolution, it is necessary the addition of an alkali compound or a heat treatment, which restrict its application in CF water treatment (Xu et al 2004, Pal et al 2005, Sableviciene et al 2005. Chemical modification, such as acetylation, arises as an excellent alternative to improve its properties as a coagulant (Xu et al 2004). Moreover, modification of starch with acetic anhydride molecules increases its solubility in aqueous media, because of the introduction of hydrophilic groups in the starch structure, which leads to increase the number of hydrogen bridges with the surrounding water molecules (Sánchez-Rivera et al 2010).…”