Optimized conditions for microencapsulation using konjac-pectin gel mixture to
increase probiotic survival rate in pasteurized drinking yoghurt
Sasivimol Chuen-Im Ahmed and Swanya Mengkred
Faculty of Agricultural Industry, King Mongkut’s Institute of Technology Ladkrabang, Chalongkrung Road,
Ladkrabang, Bangkok 10520, Thailand. Tel/Fax: 02 3264091. Email: kcsasivi@kmitl.ac.th
Abstract
Optimal conditions for microencapsulation of probiotic Lactobacillus acidophilus La5
in konjac-pectin gel bead was investigated, using water-in-oil emulsion method in which
sunflower oil was used as the continuous phase and the gel solution was the discontinuous
phase. The effect of different ratio of konjac solution (1,1.5 or 2% w/v) to pectin solution (6%
w/v) in the gel mixture on gel strength was studied. It was found that the gel strength
increased with an increase in pectin fraction and that the highest gel strength was obtained
when the ratio of 1.5% konjac solution to 6% pectin solution was 1:2. The highest
encapsulation yield and the smallest gel bead size were achieved when the ratio of the gel
mixture to oil was 20:100, compared to the ratio of 25:100 and 30:100. The suitable mixing
time was found to be 90 seconds, which rendered the highest encapsulation yield of 97% with
an average bead size of 4.97 m. The survival rate of encapsulated La5 in drinking yoghurt
stored at refrigerated temperature tended to be higher than that of the free cells. When
subjected to pasteurization at 72C for 15 seconds, the survival rate of encapsulated La5 in
drinking yoghurt increased by approximately 16%, compared to that of the free cells.
Moreover, the survival rate of encapsulated and free cells during continual refrigeration of the
pasteurized products for up to 8 weeks was about 71.8% and 43.7%, respectively. The result
also showed that pasteurization of drinking yoghurt could prevent post acidification during
refrigerated storage. Furthermore, the sensory evaluation revealed that the addition of
encapsulated cells in drinking yoghurt did not significantly change the product texture.
Keywords: Microencapsulation; Probiotic; Konjac; Pectin; Yoghurt