Renewable Energy, Vol.152, 793-798, 2020
Valorization of apple pomace using a two-step slightly acidic processing strategy
For valorization of apple pomace (AP), a two-step slightly acidic process was designed and experimentally tested using low amounts of sulfuric acid (H2SO4). First, pectin was prepared using H2SO4-assisted extraction of AP at 100 degrees C, while the remaining depectinized apple mud (DAM) was dehydrated and dried, which rendered it amenable for storage, transportation, and further processing. Second, hemicelluloses were effectively hydrolyzed and filtered out by increasing the acidic processing temperature to 120 degrees C. Therefore, the dehydration and drying problem of DAM was successfully resolved. For understanding the mechanisms underlying H2SO4 processing, the acidic reaction kinetics of DAM was investigated. We observed a significant change in the chemical compositions and structural properties of DAM. Other than the homo-polysaccharide of cellulose, the hetero-polysaccharide of hemicelluloses was selectively digested and solubilized from the intercellular spaces of DAM tissues, which facilitated moisture transfer and improved dehydration efficiency of the hot-air drying process. In total, we produced 163.2 g pectin, 334.5 g cellulose-rich substances, and 49.7 g monosaccharides from 1,000 g apple pomace. This strategy may considerably improve the economic and environmental benefits of AP utilization, and assist in developing methods for dehydration and drying of agricultural residue-liked wastes. (c) 2020 Elsevier Ltd. All rights reserved.
Keywords:Apple pomace and mud;Slightly acidic pretreatments;Selective hydrolysis;Dehydration and drying;Homo- and hetero-polysaccharides