3.4. Selection of a suitable prebiotic
Fig. 5 shows the effect of prebiotics raftilose (FOS),Hi-maize and raftiline (inulin) on the viability of probiotic organisms. Of the three prebiotics investigated, raftilose was found to best retain the viability of selected probiotic organisms (8.70 log) in fresh yoghurt after four weeks of storage at 4 C. The presence of these oli-gosaccharides reduced the rate of cell death of the saccharolytic bacteria during storage, as prebiotics were available for their utilization. Bruno and Shah (2002)
also found a marginal improvement in the viability of probiotic organisms in yoghurt containing FOS during refrigerated storage of fresh yoghurt over 4 weeks. Fig. 6 shows the effect of prebiotics on the viability of selected probiotic organisms in freeze-dried yoghurt during storage for 3 months. As shown, the viability of the probiotic organisms was comparatively but not significantly lower than the control when prebiotics were added. According to Baati, Fabre-Ga, Auriol, and Blanc
(2000), lactic acid bacteria suffer from stresses caused by changing environment. The oligosaccharides may not have been able to protect cells from injury, which may have contributed to the reduction in probiotic viability. The viability of probiotics in the control batch during storage remained higher (0.02–0.07 log) than in each of yoghurts made with added prebiotics. Hi-maize, FOS and inulin were only helpful in improving viability of probiotic organisms in fresh yoghurt during storage (Fig. 5), and had a negative effect on their viability in freeze-dried yoghurt (Fig. 6). The improved viability in
fresh yoghurt is possibly due to prebiotics providing extra solids, which tend to protect cells from injury. Oligosaccharides
used in this study are hydrocolloids, which are reported to play a protective role towards probiotic microorganisms (Desai, Powell, & Shah, 2004).
3.4. Selection of a suitable prebiotic
Fig. 5 shows the effect of prebiotics raftilose (FOS),Hi-maize and raftiline (inulin) on the viability of probiotic organisms. Of the three prebiotics investigated, raftilose was found to best retain the viability of selected probiotic organisms (8.70 log) in fresh yoghurt after four weeks of storage at 4 C. The presence of these oli-gosaccharides reduced the rate of cell death of the saccharolytic bacteria during storage, as prebiotics were available for their utilization. Bruno and Shah (2002)
also found a marginal improvement in the viability of probiotic organisms in yoghurt containing FOS during refrigerated storage of fresh yoghurt over 4 weeks. Fig. 6 shows the effect of prebiotics on the viability of selected probiotic organisms in freeze-dried yoghurt during storage for 3 months. As shown, the viability of the probiotic organisms was comparatively but not significantly lower than the control when prebiotics were added. According to Baati, Fabre-Ga, Auriol, and Blanc
(2000), lactic acid bacteria suffer from stresses caused by changing environment. The oligosaccharides may not have been able to protect cells from injury, which may have contributed to the reduction in probiotic viability. The viability of probiotics in the control batch during storage remained higher (0.02–0.07 log) than in each of yoghurts made with added prebiotics. Hi-maize, FOS and inulin were only helpful in improving viability of probiotic organisms in fresh yoghurt during storage (Fig. 5), and had a negative effect on their viability in freeze-dried yoghurt (Fig. 6). The improved viability in
fresh yoghurt is possibly due to prebiotics providing extra solids, which tend to protect cells from injury. Oligosaccharides
used in this study are hydrocolloids, which are reported to play a protective role towards probiotic microorganisms (Desai, Powell, & Shah, 2004).
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