Thermal Stability of Biodegradable Films Based on Soy Protein and Corn Starch

Abstract

Summary: In this paper, films were prepared from soy protein and corn starch in different proportions and thermal stability and kinetic parameters were determined through degradation reactions in an inert atmosphere. Solid residues and decomposition products were identified by infrared spectroscopy. Films from corn starch were less thermally stable than soy protein films. The films containing both components had lower thermal stabilities when compared to those of the pure biopolymers. The mechanism of starch thermal degradation seems to occur in a single step, which can be confirmed by the constant E-values during the thermal degradation reaction. For the pure protein and its mixtures an increase in the activation energy was observed during the reaction. Solid residues for protein at different temperatures showed mainly bands related to C O stretching, angular deformation of N-H and C-H groups. For starch, absorptions related to free and bound O-H, C O stretching of CO 2 , CO and carbonyl compounds were observed. For the 50/50 mixture bands related to soy protein and corn starch were observed. The gaseous products for soy protein showed absorptions related to CO 2 , CO, C O, NH 3 and C-H stretching. For pure starch absorptions related to O-H stretching from alcohol, C O from CO 2 , CO and carbonyl compounds. The 50/50 mixture had the same characteristics as pure soy protein and corn starch.

Properties of chitosan/soy protein blended films with added plasticizing agent as a function of solvent type at acidic pH

“…Soares et al [36] found similar stepwise degradation mechanism of soy protein. For 50/50 blend films, the thermal degradation began earlier compared to pure films.…”

Information Architecture Practice: An Interview with Gayle Curtis, Modem Media

“…Figure 3 shows ATR‐FTIR spectra of (a) SPC‐100, (b) SAA‐20, (c) SAG‐20, and (d) SPG‐20 films, all containing 20 wt% SPC/gelling agents) sorbitol. Typical soy protein represents three amide bands at 1 625, 1 536, and 1 238 cm −1 which are attributed to amide I band (CO stretching vibration), amide II band (NH deformation), and amide III band (CN stretching and NH vibration), respectively 33, 34. All ATR‐FTIR spectra show one strong band at 1 072 cm −1 which is mainly attributed to COH bending from sorbitol which was added to all films as a plasticizer 35.…”

Biodegradable protein‐based films from plant resources: A review

“…For mixtures of protein and starch, a synergistic effect was observed when compared to pure polymers. This synergistic behavior may be related to changes in the reaction mechanism during the thermal degradation reaction [24].…”