Optimization of bleaching process for cellulose extraction from apple and kale pomace and evaluation of their potentials as film forming materials

Abstract

Celluloses from apple and kale pomaces were extracted through sequentially chemical treatments, characterized, and evaluated for the film forming property. Since bleaching step is critical to cellulose quality, bleaching conditions including concentration of bleaching agent (NaClO) (0.5–3 %), temperature (60−80 °C) and time (1−2 h) were optimized. NaClO concentration and temperature exhibited significant impact on the quality of celluloses. Excessive bleaching conditions caused severe oxidation of celluloses and significantly reduced their dimension. The optimum bleaching conditions for apple pomace were identified as 1–1.5 % NaClO at 80 °C for 1 h, resulting in cellulose yield of 7.9 %, water retention value of 2.96, and whiteness index of 72.36. Morphological analysis of optimum apple pomace-celluloses revealed their long-shaped structure with 500−750 μm in length and 20−25 μm in width. The prepared cellulose films had high transparency and good mechanical strength. This study provided new insight in converting fruit processing byproducts into high quality celluloses.