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Comparison of Structural and Thermal Properties of Films of Pure Web Protein Derived from Orthaga exvinacea, Pure Starch and Blend of the Two

N Sajitha

Studies were conducted to compare the structural and thermal properties of pure films of starch and silk protein purified from the web of the pyralid moth, Orthaga exvinacea, a pest of mango tree in India. Silk protein was isolated, purified and introduced into starch solution. The mixture was poured into Petri dishes, to prepare the blended film. The films of pure protein and starch were also prepared. These films were dried and subjected to Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric-differential thermal analysis (TG-DTA). The structural studies showed that the blend film had both the proteineous and saccharide characteristics of silk protein and starch. Even though, the amide II band contributed β-turn structure to the protein, α-helix, most unstable conformation was associated with the same amide band in the blended film. Moreover, amide A and B bands were absent in the blended film. These had been noticed in its thermal properties also. The temperature of maximum degradation of the blend was almost same as those of their respective pure films. The study suggests that for making a structurally and thermally stable film, an increase in the content of protein in the starch solution is necessary. Moreover, the optimization of various processing conditions may result in the formation of a blend, which is the most apt one for the non-textile industry.