Hydrolysis Of Milkfat And Microcapsulation Of Hydrolysate

An investigation was conducted on the hydrolysis of milkfat catalyzed by Candida lipalytica lipase and the microencapsulation of the hydrolysate.On the basis of single factor experiments, response surface analysis was applied to determine the optimal conditions of hydrolysis. The optimal conditions included milkfat concentration 50.7%; pH 15; lipase 317.3U/g; temperature 40 C; shaker rotation 180r/min.The results of instrumental analysis and sensory evaluation indicated the highest acceptance was found for the product which was hydrolyzed 6hr under the optimal conditions. The method of simultaneous distillation-extraction was employed to extract the volatile components of the hydrolysate. The compounds of the characteristic milk flavor of the extract were isolated and identified by GC-MS. The chemical components included: 3-hydroxy-2-Butanone 6.23%, 2-Nonanone 2.98%, 5- Dodecanol 0.92%, Acetic acid 1.29%, 2-Undecanone 1.13%, Butyric acid 7.52%, 2-tridecanone 0.56%, Hexanoic acid 17.01%.The microencapsulated hydrolysate was produced by spray-drying with gelatin and maltodextrin as wall material. The ratio of gelatin to maltodextrin was 1:4. The optimal conditions of emulsion were determined by single factor experiments and orthogonal design: gelatin :maltodextrin 1:4; emulsifier 2% which was comprised of mono-glyceride and sucrose ester 1:3; core/wall 1:1; the temperature of emulsion 60 C; the quantity of added water 50%. Efficiency of encapsulation was 92.06% under the condition of spray-drying: inlet temperature 180~190 C, outlet temperature 80~90 C, feeding rate 1.81/hr.The retention of total volatiles collected by SDE was 91.02%. Compared with the melting peak of microencapsulated milkfat, 180 C, that of microencapsulated hydrolysate was decreased to 95 C as a result of DSC analysis. Environment Scanning Electron Microscopy (ESEM) was applied to view the microstructure of microencapsulated product. Good results were obtained. Moisture of the powder was 2.82%, fat content 46.55%, bulk density 255ml/g, full reconstitution in 60 C water, powder flowability 40. No significant flavor difference (P>0.05) was showed between experimental and market samples.