Lactobacillus acidophilus LA-5 has poor survivability in yoghurts. This study aims to microencapsulate L. acidophilus LA-5 using polymerised whey protein as wall material and evaluate its survivability and effects on physiochemical properties of yoghurts. The microencapsulation yield was 92.90% and average beads size was 744 mu m. Microencapsulated L. acidophilus LA-5 showed higher survival at simulated gastrointestinal conditions. Microencapsulated L. acidophilus LA-5 had improved survivability (similar to 10(6) cfu/mL) than free cells (similar to 10(4) cfu/mL) after digesting by simulated intestinal juice (6 h) in yoghurts during 10-week storage. Microencapsulated L. acidophilus LA-5 improved the firmness and protein content and decreased the spontaneous whey separation and synaeresis of yoghurts significantly (p < 0.01). Changes in pH and free microorganism population of yoghurts during storage were not affected by adding microencapsulated L. acidophilus LA-5. Microencapsulation of L. acidophilus LA-5 using polymerised whey protein as wall material improved its survivability and the physiochemical properties of the yoghurt.