Characteristics of crystalline and amorphous fractions of date-pits as treated by alcohol-water pressure cooking

Abstract

Date-pits are waste from date fruit processing industry and their valorisation as a lignocellulose biomaterial could generate economic gain. In this work, defatted date-pits (DDP) from whole date-pits (WDP), was soaked in alcohol-water followed by pressure-cooking. Two fractions of date-pits were developed, one as residue fraction (REP) and another one was supernatant fraction (SUP). REP showed higher level of hemicellulose and lower level of lignin (P < 0.05) compared to SUP. Similar water absorption, increased hygroscopicity, and decreased solubility were observed for REP compared to SUP. SEM showed that REP with bigger size particles as compared to the SUP fraction. SUP fraction showed two glass transitions, while REP showed single glass transition. Total specific heat changes of REP, and SUP fractions were 149 and 1032 J/kg oC, respectively, which indicated that SUP is mainly amorphous in composition. This was also supported by XRD data having Ruland-crystallinity of 52.0% (i.e. REP) and 9.6% (i.e. SUP), respectively. FTIR analysis indicated different molecular structure of SUP as compared to REP fraction as evidenced from the highest energy absorption for all selected functional groups. Overall, the results showed that this extraction method was effective to produce two distinctive fractions of date-pits with varied crystallinity.