Two strains of lactic acid bacteria(Lactobacillus delbruekii ssp.Bulgaricus and Streptococcus salivarius ssp.Thermophilus)were immobilized separately in liquid-core alginate capsules and used for continuous inoculation-prefermentation of milk for yoghurt production in a stirred tank reactor.The result showed that the coagulum time was shortened with the increase of temperature under the lower level pH.The effect of stirring speed on the dilution rate was significant.The dilution rate decreased as stirring speed increased.The inoculation of pre-fermented milk(total number of bacteria) were unaffected by pre-fermentation temperature,pH and stirring speed.In all cases,pre-fermented milk was inoculated at 108 CFU/mL.