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Keywords:

  • Coconut oil;
  • Glycerol monolaurate;
  • Glycerolysis;
  • Immobilized lipase;
  • Molecular distillation

In order to study the potential of producing glycerol monolaurate (GML) under a mild condition, enzymatic catalyzed glycerolysis in microemulsion system and molecular distillation were used to produce glycerol monolaurate-enriched MAGs from coconut oil. For the process of glycerolysis, the catalytic abilities of three lipases were compared, and the reaction conditions were studied. Moreover, evaporator temperatures of two-step molecular distillations were optimized. The results showed that the suitable lipase was Novozym 435, and the optimum glycerolysis parameters were molar ratio of coconut oil to glycerol 1:4; the concentrations of Novozym 435 and sodium (bis-2-ethyl-hexyl) sulfosuccinate 8 and 16%, respectively; and the reaction temperature 50°C. Under these conditions, with a 240 min reaction time, glycerides which contained 62.5% MAGs, 30.4% DAGs, and 5.8% TAGs were obtained. The content of GML was 29.3% and the acid value (AV) was 8.0 mg KOH/g. Then, by two-step molecular distillations conducted at 90 and 120°C (0.5–1.0 Pa), the content of GML and MAGs were efficiently increased to 60.0 and 97.6%, respectively. Meanwhile, the content of DAGs and the AV were decreased to 2.0% and 0.02 mg KOH/g.

Practical applications: Glycerol monolaurate (GML), a surfactant, has been widely used as emulsifier and preservative in the food industry. However, the traditional production of GML by chemical esterification under high temperature is complicated and energetically costly. The proposed method provideds mild conditions to produce GML. For the first time the GML produced from enzymatic glycerolysis of coconut oil and its concentration by molecular distillation were investigated.