دانلود رایگان مقاله خصوصیات کاه سویا و پروتئین ایزوله سویا - فیلم های کامپوزیت کاه

ABSTRACT

This work investigated changes in the chemical composition and structure of soybean straw (SS) treated with alkali (NaOH 5% and 17.5%) and bleached with hydrogen peroxide (H2O2) or sodium hypochlorite (NaOCl). Removal of the amorphous constituents increased the degree of crystallinity and the content of cellulose fibers particularly after reaction with high concentrations of alkali. Treatment with NaOH 17.5% contributed to the allomorph transition from cellulose I to II regardless of the bleaching agent, but H2O2 as bleaching agent promoted more effective delignification. This work also evaluated the potential use of treated and non-treated SS as reinforcement filler in soy protein isolate film (SPI). Films added with treated SS presented higher mechanical resistance, lower elongation at break, and lower solubility in water. Addition of non-treated SS did not affect the properties of the SPI film significantly. The low solubility and the reasonable water vapor permeability of the composite films make them suitable packaging materials for fresh fruit and vegetables.

4. Conclusions

Chemical treatments of soybean straw including reaction with alkali and bleaching yielded materials with higher cellulose content as confirmed by TGA and FTIR analysis. The cellulose content in the fibers was attributed to effective removal of hemicelluloses, lignin, and other inert and inorganic materials. The degree of cellulose crystallinity was increased as the amorphous constituents were removed during the treatments. During these treatments, the use of high concentration of NaOH contributed to the allomorph transition from cellulose I to II, regardless of the bleaching agent. These specific differences can influence the application ofthe resulting fibers. The treated SS performed better as reinforcement filler in SPI films. The filler increased the mechanical resistance of the film because it promoted stronger interactions between the polar groups in the protein and the hydroxyl functionalities in the treated fibers. The soybean straw treated with hydrogen peroxide affected both the mechanical properties and the solubility of the film, mainly due to the removal of lignin. The addition of 1% of fibers did not modify the water vapor permeability of the film significantly. Different percentages of fillers should be evaluated for an effective reduction in WVP values.