Probiotic encapsulation by spray drying using konjac glucomannan hydrolysate as wall material and its application in ice cream

Abstract

This research aims to study encapsulation efficiency of cell probiotics by using Konjac glucomannan hydrolysate (KGMH) under spray drying. KGMH was prepared from Konjac glucomannan solution (KGMS) at different concentrations. Lactobacillus casei was used in this study as it is commonly used in food industry and resistance to heat. The effect of wall material (HGMH) concentration on encapsulation efficiency of the cell probiotic was evaluated. Probiotics culture was prepared by inoculating in sterile MRS broth and incubated at 37°C for 48 hours, the cells were harvested in the early stationary phase. Konjac glucomannan solution was hydrolysed by mannanase at 40°C for 4 hours. Then, probiotic solution (10 log CFU/ml) was mixed with KGMH at concentration of 15%, 20% and 25% (w/w). Spray drying condition was kept at constant inlet air temperature of 170°C, outlet air temperature of 85°C and feed flow rate of 10 mL min-l. Encapsulated probiotic with KGMH at concentration of 25% (w/w) exhibited the highest encapsulation efficiency (95.4 %), water activity of 0.198 and moisture content of 4.38 % (w.b.). For application in ice cream, microcapsules of probiotic encapsulated with KGMH at concentration of 25% with and without 10% (w/w) trehalose were then mixed into milk ice cream separately. The ice cream was stored at -18°C for one month. The survival rate of microencapsulated probiotic cells and free cells probiotics in the ice cream were measured. It was found that microcapsule of KGMH at concentration of 25% (w/w) with 10% (w/w) trehalose gave higher survival rate of probiotics cell (> 90%) in ice cream under freezing temperature than KGMH at concentration of 25% (w/w) and free cell probiotics during storage, respectively.