Hydrolysis, glycerolysis and alcoholysis of anhydrous milk fat by lipases in supercritical carbon dioxide.

摘要

Modification of milk fat by lipases from porcine pancreas (PPL), Pseudomonas sp. (PS-30) and Lipozyme{dollar}spcircler{dollar} in microaqueous systems was investigated. Various pressures were examined to assess feasibility of using supercritical carbon dioxide (SC CO{dollar}sb2){dollar} to control lipase activity and product extraction of modified butteroil.; Tricaprin or anhydrous milk fat (AMF) hydrolysis by PPL was investigated at different pressures (0.1 to 27 MPa), temperatures (40{dollar}spcirc{dollar} or 60{dollar}spcirc{dollar}C) and enzyme water activities (0.28 and 0.47, {dollar}rm asb{lcub}w{rcub}).{dollar} Tricaprin was completely solubilized in SC CO{dollar}sb2,{dollar} whereas AMF existed in liquid and supercritical phases.; Maximum tricaprin hydrolysis occurred at 40{dollar}spcirc{dollar}C and 0.47 a{dollar}rmsb{lcub}w{rcub}{dollar} at atmospheric pressure and 40{dollar}spcirc{dollar}C, 27 MPa and 0.28 a{dollar}rmsb{lcub}w{rcub}{dollar} under supercritical conditions. Extent of hydrolysis was greater at atmospheric pressure than at 27 MPa. For AMF hydrolysis, fatty acid (FA) concentration was similar in liquid phase at 13.5 MPa for both reaction temperatures and comparable to 40{dollar}spcirc{dollar}C and atmospheric pressure. At 27 MPa, FA concentration in both liquid and supercritical phases was greater than observed at 40{dollar}spcirc{dollar}C and atmospheric pressure.; Immobilized PS-30 (polypropylene beads) had increased thermal stability up to 60{dollar}spcirc{dollar}C when incubated for 24 hours. Less than 6% enzyme activity loss was observed at temperatures less than 60{dollar}spcirc{dollar}C with no moisture and less than 20% activity loss with moisture. Glycerolysis of AMF by immobilized PS-30 was investigated at both atmospheric pressure and 13.5 MPa. Overall, less glycerolysis occurred under supercritical conditions. As the reaction progressed, more FA, monoacylglycerols (MAG) and diacylglycerols (DAG) accumulated in the supercritical phase, whereas greater proportions of triacylglycerol (TAG) were observed in the liquid phase.; Lipozyme{dollar}spcircler{dollar} was used to synthesize fatty acid ethyl esters from butteroil and ethanol (EtOH). At atmospheric pressure, alcoholysis was limited by EtOH concentration. Concentrations greater than 20% decreased ester concentration after 24 hours. After five days, ester concentration at 25% EtOH addition was similar to 5% EtOH at 24 hours. More ethyl butyrate and ethyl palmitate were formed at atmospheric pressure than in SC CO{dollar}sb2.{dollar} Under supercritical conditions, more short chain ({dollar}{dollar}C16:0) were observed at 10% and 25% EtOH, respectively.