| The medium- and long- chain glycerides (M/LCG) were prepared by enzymatic transesterification of octanoic acid and molecular distillation residue of monoglyceride with Lipozyme TL IM as catalyst. The effects of molar ratio of substrate (molecular distillation residue and octanoic acid), reaction temperature, reaction time and dosage of enzyme on the content of octanoic acid-containing glycerides and the entrapment efficiency of octanoic acid were investigated by single factor experiment. And the optimal process conditions were obtained as follows: reaction temperature 65?℃, molar ratio of molecular distillation residue to octanoic acid 6∶?4, reaction time 6 h and dosage of enzyme 15%. Under the optimal conditions, the content of diglycerides in M/LCG was 50.73%,and the entrapment efficiency of octanoic acid was 15.35%. The M/LCG obtained by optimal conditions was purified by column chromatography with silica gel as adsorbent, n-hexane-ether-formic acid (volume ratio 45∶?25∶?1) as eluent, and medium- and long- chain diglycerides (M/LCD) with DAG content 88.24% was obtained, and main were sn-1,3 DAG. The characteristics of the purified M/LCD was measured by DSC and XRD, and the results showed the melting point of M/LCD was 60.34?℃, and there was obvious polymorphisms, mainly coexistence of β and β′ type crystal form. The thermodynamic properties and crystal form of M/LCD would provide a certain theoretical basis for its potential application in emulsion. |
