Application Of Non-aqueous Phase Lipase Catalysis In The Preparation Of Esters Food Additives

L-ascorbyl palmitate (L-AP) and L-ascorbyl stearate(L-AS) are important ascorbic acid derivative and nutritional fat-soluble antioxidants, often used in infant foods. Ethyl caproate is the major aroma component of liquor, widely used in the field of food flavoring. Dodecyl nipagin ester is a safe and effective preservative.Synthesized of the four kinds of esters of food additives by lipase-catalyzed in non-aqueous phase were studied in this paper.The first part, synthesized L-AP by a direct esterification from L-ascorbic acid and palmitic acid by lipase-catalyzed in t-butyl alcohol. Controlled L-ascorbic acid to palmitic acid molar ratio of 1: 1.8, the optimum reaction conditions: 0.25g lipase and 1.07g ascorbic acid, reaction temperature 50℃, reaction time 48h, the yield reaches 85.0%. Reaction was carried out in batch stirred tank, the maximum yield reaches 89.0%. The product was crystallized of the reactant by the toluene, its purity reaches 98.2%.The second part, synthesized L-AS by a direct esterification from L-ascorbic acid and stearic acid by lipase-catalyzed. The product was separated and purified from the reaction solution, the structure of product was characterized by IR and MS, showed that the product was L-AS. Controlled the molar ratio of ethanol to acid of 1:2, other reaction conditions were 0.1Og lipase and 1.20g ascorbic acid, temperature 55℃, time 48h, the yield reaches 64.7%.The third part, the effects of lipase-catalyzed ethyl caproate conditions were studied, purified ethyl caproate from the reaction solution. The structure of product was characterized by IR, showed that the product was ethyl caproate. The optimum reaction conditions:0.1Og lipase, 10mmol hexanoic acid and 13mmol anhydrous ethanol in 20mL heptane, reaction temperature 50℃, reaction time 6h, the highest esterification rate reaches 97.9%.The fourth part, synthesized dodecyl nipagin ester from p-hydroxybenzoic acid and dodecyl alcohol catalyzed by lipase was studied. The effects of organic solvents to esterification was investigated, haven't found a suitable solvent to promote the reaction, may be the activation energy required for the reaction higher than other esterification.