Influence of Lactulose on the Survival of Probiotic Strains in Yoghurt

Dairy products containing lactic acid bacteria are often consumed because of the health-promoting activities of some strains of these bacteria as probiotics. It is important that these strains survive the acidic environment of the product since only microorganisms that are alive can be functionally active. This report describes the potential of luctulose to improve the survival of available probiotic strains in yoghurt. Yoghurt with and without lactulose were produced in which these strains were present. The survival of the probiotic strains was monitored for 5 weeks at 4oC. The main conclusions are: Lactobacillus rhamnosus and Bifidobacterium bifidum were found to be extremely stable during the 5 week storage period and survives slightly better the presence of lactulose. Key word: Lactulose lactobacillus bifidobacter probiotic yoghurt INTRODUCTION Yoghurt preparation: Yoghurt milk (skim milk +1% Lactobacillus and Bifidobacterium species are well lactulose was pasteurized for 5 min at 85oC and known for their application in fermented milk products. cooled to 32oC and inoculated with 0.63 ml 1:10 Consumption of these bacteria is frequently related to the diluted Streptococcus thermophilus and probiotic health promoting activities of some strains [1, 2]. Strains bacteria include of Lactobacillus rhamnosus and with beneficial characteristics are referred to as probiotics. Bifidobacterium bifidum. After gently mixing the The application of these strains in fermented dairy yoghurt was divided into bottles and were incubated products requires the use of adapted manufacturing at 32oC for 14.5 h. during the incubation, the pH was technologies. The problem of survival the strains in the measured every 30 min. The end samples were acidic environment of the product must be improved since homogenized and stored at 4oC. These samples were only micro-organisms that are alive can be functionally used for evaluation of the survival of the probiotic active. Lactulose is semi synthetically disaccharide and bacteria [4]. know for its stimulating effect on intestinal lactic acid bacteria, especially Bifidobacterium species. Besides it Yoghurt analyses: The survival of the yoghurt bacteria might have the potential to improve the survival of was tested during 5 week period by plating appropriate probiotic bacteria in fermented dairy product and its dilutions in a sterile solution of 0.85% Nacl and 0.1% application as a prebiotic ingredient in several food peptone on MRS-agar (merck) incubation of all probiotic products. The present study influence of lactulose on the strains was performed at 37oC under an aerobic condition survival of two strain of probiotic bacteria in yoghurt for 3 days (1). stored at 4oC was studied [1, 3]. MATERIAL AND METHODS Bacterial strains: Lactobacillus rhamnosus and faster acidification of the yoghurts during 14.5h Bifidobacterium bifidum were supplied by Hunsens’s incubation period and lactoluse did not have any effect company. on acidification. (W/V) skim milk powder) containing 0, 1 and 3% RESULTS AND DISCUSSION The addition of probiotic strains resulted in a slightly World Appl. Sci. J., 3 (1): 88-90, 2008 89 Table 1: Influence of lactulose on pH and number of probiotic becteria Number of probiotic Probiotic strain Lactulose (%) pH bacteria (CFU ml ) 1 Lacto bacillus rhamnosus 0 4.32 1.0×108 Lacto bacillus rhamnosus 1 4.33 1.0×108 Lacto bacillus rhamnosus 3 4.32 1.1×108 Bifido bacterium bifidum 0 4.28 1.6×107 Bifido bacterium bifidum 1 4.29 2.3×107 Bifido bacterium bifidum 3 4.29 2.4×107 Fig. 1: Development of the pH during storage of the yoghurts 0% lactulose Fig. 2: Development of the pH during storage of the yoghurts 1% lactulose Fig. 3: Development of the pH during storage of the yoghurts 3% lactulose Fig. 4: Stability of for two probiotic strains during the storage of the yoghurts 0% lactulose Fig. 5: Stability of for two probiotic strains during the storage of the yoghurts 1% lactulose Fig. 6: Stability of for two probiotic strains during the storage of the yoghurts 3% lactulose After cultivation, the pH and number of probiotic in the yoghurts were determined, the results are listed in the Table 1. from this table, it can be concluded that there is no effect of lactulose on the final pH. Also, a small decrease in pH was observed during storage of the yoghurt at 4oC (Fig. 1-3). This decrease was most serve in yoghurts containing either lacto bacillus rhamosus and Bifidobacterium bifidum. No effect of lactulose was observed on this process. The prbotic strains were surprisingly resistant to the storage condition (Fig. 4-6) and no effects of lactulose World Appl. Sci. J., 3 (1): 88-90, 2008 90 was observed for these strains. Except of the yoghurt 2. Ocer, D. and S. Akins, 2005. Effect of linulin and containing 3% lactulose was observed protective effect lactulose on survival of lactobacillus acidophilus and after 4 week of storage (Fig. 6), Bifidobacerium bifidum Bifidobacterium Bifidum in acidophilus youghurt. remained higher in the presence of lactulose throughout Food Sci. Technol. Intl., 11: 19-24. the test period. 3. Chall, A., J.R. Rao, C.B. Chawan and Shackelfor, 1997. Lactobacillus rhamnosus and Bifidobacterium L. Bifidobacterium longum and lactulose suppress bifidum did not lose their viability during the 5-week azoxymethane-induce colonic aberrant crypt foci in storage period and a protective effect of 3% lactulose was rat. Carcinogenesis, 18: 517-521. found after 5 week of storage (Fig. 6). The use of 4. Marteau, P. and M.C. Boutron-Ruault, 2002. lactulose might the effective for strains having Nutritional advantages of probiotics and intermediate survival behariour. prebiotics. Br. J. Nutr., 87: S153-S157.