99D-20

Lactobacillus reuteri is a probiotic bacterium that is increasingly being used in foods. The viability of Lb. reuteri in foods is essential in order to deliver its desirable health benefits to the consumer. Microencapsulation should be able to protect the bacterial cell against the harsh environment often encountered during food processing and also during passage through the acidic pH of the stomach.

This study was designed to find the most suitable method and wall material for microencapsulation of Lb. reuteri.

Lactobacillus reuteri was encapsulated using alginate, alginate plus starch, κ carrageenan with locust bean gum, or xanthan with gellan by both extrusion and phase separation methods. The morphology of the microcapsules was studied using scanning electron microscopy (SEM). The resistance of these microcapsules to simulated gastric juice and the viability of the contained bacteria stored under refrigeration were then studied.

The shape of the microcapsules produced varied with the method and type of wall material. On extrusion, alginate and alginate with starch formed good spherical capsules whereas the other two wall materials yielded imperfect spheres. The shape of the capsules formed by phase separation was also irregular. The average size of the capsules was 2-3 mm for the extrusion method and 20μm – 1mm by phase separation. Microencapsulation using alginate with starch (by extrusion) and κ carrageenan with locust bean gum wall matrix (phase separation) were found to provide greater protection against gastric juice. On refrigerated storage, bacterial viability in microcapsules prepared by both methods and with all wall materials decreased by ≥ 2 log cfu/g at the end of 15 d. Methods to further improve viability of encapsulated bacteria during refrigerated storage are being investigated.

The method of encapsulation and the wall material are factors which influence survival of Lb. reuteri during food processing and passage through the GI tract.