Chemical Composition of Apricot Pit Shells and Effect of Hot-Water Extraction

Agricultural residues, such as corn stover, wheat straw, and nut shells show promise as feedstocks for lignocellulosic biorefinery due to their relatively high polysaccharide content and low or no nutritional value for human consumption. Apricot pit shells (APS) were studied in this work to assess their potential for use in a biorefinery. Hot water extraction (HWE; 160 °C, 2 h), proposed to remove easily accessible hemicelluloses, was performed to evaluate the susceptibility of APS to this mild pretreatment process. The chemical composition of APS before and after HWE (EAPS) was analyzed by standard methods and 1H-NMR. A low yield of the remaining HW-extracted APS (~59%) indicated that APS are highly susceptible to this pretreatment method. 1H-NMR analysis of EAPS revealed that ~77% of xylan present in raw APS was removed along with ~24% of lignin. The energy of combustion of APS was measured before and after HWE showing a slight increase due to HWE (1.61% increase). Near infrared radiation spectroscopy (NIRS), proposed as a quick non-invasive method of biomass analysis, was performed. NIRS corroborated results of traditional analysis and 1H-NMR. Determination of antioxidizing activity (AOA) of APS extracts was also undertaken. AOA of organic APS extracts were shown to be more than 20 times higher than that of a synthetic antioxidizing agent