Valorisation and Characterization of Allium cepa var. aggregatum Biowastes for the Production of Microcrystalline Cellulose

Purpose Shallot (Allium cepa var. aggregatum) expels peel, stalk and petiole as major waste streams during harvesting and industrial processing. The study investigates effect of pre-treatments and process parameters on extraction of a-cellulose and subsequently Microcrystalline Cellulose (MCC). Method The extraction of cellulose and MCC was carried out by two pre-treatments such as hot water (60 degrees C) and autoclave method (121 degrees C) along with combined hydrolysis of alkali-bleaching-acid. The efficiency of pre-treatment with time, temperature and concentration of NaOH were evaluated. Result The recovery yield of MCC from cellulose was high in stalks and peel (autoclave pre-treated) and petiole (hot water pre-treated) with 79.39, 59.23 and 55.63% respectively. The FTIR spectra of samples showed that removal of lignin and hemicellulose was better in autoclave pre-treated samples. Scanning electron micrograph showed the morphological modifications in both pre-treatments. Crystallinity of extracted MCC was analysed with X-ray diffraction method and found high in hot water assisted petiole and autoclave assisted samples of petiole and stalk with 83.74, 79.93 and 76.75% respectively. The thermal resistance of extracted samples was analysed with DSC. The results of various parameters were compared with commercial MCC and showed close proximity. Conclusion The autoclave assisted pre-treatment was better for the effective transformation of cellulose to MCC with combined chemical hydrolysis which was technically easier, economical with less energy consumption. In a nutshell, selected shallot wastes proved to be source of superior quality microcrystalline cellulose with potential for commercialization.