Survival and activity of selected probiotic organisms in set-type yoghurt during cold storage

The growth and metabolism of two probiotic organisms (L. acidophilus LAFTI (R) L10 and Lactobacillus casei LAFTI (R) L26) and a regular yoghurt culture (L. delbueckii ssp. bulgaricus Lb1466 and Streptococcus thermophilus SO 342) were studied in yoghurt containing 0.5%, 1.0%, and 1.5% (w/v) of high amylose corn starch powder (Hi-maize (R)) or inulin. Viable cell counts of probiotic organisms, their metabolites and proteolytic activities, and viscosity of the yoghurts were determined during refrigerated storage for 28 d at 4 degrees C. In the presence of inulin, cultures showed better retention of viability (8.0 log cfu g(-1)) in comparison with that of Hi-maize, which had a reduction by one log cycle. Lower concentrations of 0.5-1.0% Hi-maize improved (P < 0.05) the production of propionic acid and also increased proteolytic activity of probiotic organisms substantially. A greater release of free amino acids may have sustained better growth of the organisms in yoghurts. Supplementation with either Hi-maize or inulin increased the viscosity of probiotic yoghurts significantly (P < 0.05). (c) 2006 Elsevier Ltd. All rights reserved.