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

Abstract

Banana and maize starches were acetylated with acetic anhydride in the presence of different levels of catalytic agent (iodine) using microwave heating. Degree substitution, he Fourier transforms infrared (FT-IR) spectra, the morphological properties, the gelatinization and retrogradation characteristics, the pasting property and X-ray diffraction pattern were evaluated. The FT-IR study showed that acetylation was produced in both starches, a strong absorption band at 1740 cm À1 , and this signal rose when the concentration of iodine increased; this pattern was corroborated with degree substitution of both starches. SEM revealed more exo-corrosion and fusion in acetylated maize starch granules. Acetylated banana starch had higher crystallinity level than maize starch, and the crystallinity level decreased when the catalyst concentration increased. Similar pattern was show for the average temperature and enthalpy of gelatinization. In general, the acetylation retards the starch retrogradation, but at longer storage time this effect was minimized. Difference in the retrogradation level was found between both starches. Using microwave heating and different iodine concentrations as catalyst is possible produce acetylation of starch with specific physicochemical characteristics.

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

“…Some other changes in intensity were also observed in peaks that are characteristics of anhydrides, such as the one at 1150 cm -1 that is related to the stretching bond of -CO group. This confirms that acetylation was achieved in the plantain starch, as reported by other authors in similar studies (Adebajo and Frost 2004, Xu et al 2004, Xu and Hanna 2005, Bello et al 2010.…”

“…However, the percentages and degrees of substitution were higher in this work, thus proving the versatility of the method that was implemented. Even though all of the compared results are below the ones that were obtained in the current research, it must always be taken into consideration that both, acetylation percentage and degree of substitution depend on the vegetal source and granular structure of the native starch (Xu et al 2004, Sánchez-Rivera et al 2010). …”

“…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). …”

“…In addition, a slight gradual surface damage started to be observed for the high acetylated starch sample (HAS). Although it has been reported that the acetylation of the starch allows an increase on its coagulant activity in the CF application, it is possible that the introduction of this chemical group into the starch structure can affect its integrity, changing its mechanical properties (Xu et al 2004, Bello et al 2010). …”

“…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).…”