A one‐step approach for esterification of zein with methanol

Abstract

Zein (corn protein) was reacted with methanol in the presence of para‐toluenesulphonic acid under mild conditions to give a material formed by esterification of predominantly the amide groups of the protein. The formation of methyl zeinate was confirmed by proton NMR. The new signal appeared at 3.67 ppm in zein methylation product, which is absent for pure zein can be assigned to the protons of the CH3 group of an ester. The strong CO stretching vibration due to the presence of ester group in the region of 1739 cm−1 in case of methylated zein was also noticed from FTIR studies. The increase in the C : N atom ratio in the zein methylation product obtained from elemental analysis results further indicates the conversion of a significant proportion of the CONH2 groups in zein to COOCH3 groups in the esterified product. The methylated product had glass transition temperature about 20°C lower than that of the unmodified zein. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Water‐repellent films from corn protein and tomato cutin

“…In the ATR-FTIR spectra, the peaks at around 1730 cm −1 and 1167 cm −1 are attributed to the C=O and C-O stretching vibrations, respectively, of methyl ester groups. 27 These peaks were absent in non-modified zein, in agreement with our previous study (which also used non-modified zein). 51 F I G U R E 3 Optical microscopy images of zein films prepared in aqueous ethanol solutions (90% ethanol and 10% water, volume based) dry (top left), after exposure to ethanol (top right) and DI water (bottom left and right) for 12 h at 20 C. the scale bar is 100 μm in all images [Color figure can be viewed at wileyonlinelibrary.com] Figure 5 shows the deconvolution of the amide I band for films obtained using M-zein or PM-zein.…”

“…Zein was modified using two approaches, adapted from a previous study. 27 In these two approaches, zein was methylated by esterification of carboxylic acid groups (-COOH) and direct amide (-CONH 2 ) esterification, as shown in Scheme 1. In the first approach, zein (10.1 g), p-toluene sulfonic acid (50.1 g), and methanol (500 ml) were combined in a round bottom flask and stirred, yielding a clear, yellow solution.…”

“…26 However, due to the heterogeneous nature of cast zein films made with such plasticizers, separation of the different components can cause issues such as inconsistent mechanical and surface properties. 27 Chemical modification of amino acid functional groups has been explored as a means to improve mechanical properties of zein and plasticizer inclusion. 27,28 This approach was also used in our current study, where zein was methylated by esterification of carboxylic acid groups (-COOH) and direct amide (-CONH 2 ) esterification.…”

“…These plasticizers could improve the mechanical properties of films by reducing the glass transition temperature of zein 25 and by separating zein molecules, hence facilitating their molecular movement 26 . However, due to the heterogeneous nature of cast zein films made with such plasticizers, separation of the different components can cause issues such as inconsistent mechanical and surface properties 27 . Chemical modification of amino acid functional groups has been explored as a means to improve mechanical properties of zein and plasticizer inclusion 27,28 .…”

Electrospun Zein Fibers Incorporating Poly(glycerol sebacate) for Soft Tissue Engineering

“…FTIR analysis of neat zein revealed a new peak at around 1739 cm −1 after 1 and 7 days, which could be attributed to C=O stretch vibrations due to the presence of ester groups in methylated zein [ 44 ]. This peak completely disappeared after 14 days of immersion.…”