Introduction: Yogurt is a fermented dairy product and due to its suitable sensory and functional properties, it is regarded as one of the most desirable dairy products. In recent years, suggestions have been made to consumers to use Yogurts containing probiotics.Prebiotics are added to probiotic products to improve the sensory and technological properties of the food products. The Yogurt products that contain both probiotic bacteria and prebiotic components are called symbiotic Yogurt. The aim of this research work is to investigate the production and storage of symbiotic Yogurt.Materials and Methods: In this study prebiotics including Lactulose, Inulin, and Oligofructose as single, double and triple mixtures, and lactobacillus casei were used to produce synbiotic Yogurt. Sensory evaluations of the samples were carried out one day after production and the best sample was selected. In the next stage, the samples were compared with the control sample (probiotic Yogurt without prebiotic) stored at 4oC for 21 days and their sensory properties and textural analysis (texture firmness) were carried out.Results: The results showed that the samples containing Inulin, Lactulose – Inulin, and Lactulose – Oligofructose had the best sensory properteis. These samples and the control were refrigerated for 3 weeks at 4oC. The results suggested that the sample contained Lactulose – Inulin had the best flavor and the control had the lowest score. The best score concerned with texture and texture firmness was the sample containing Lactulose- Oligofructose while the control sample had the lowest score in term of firmness. There were not significant differences between the samples' color. The results suggested positive effect of prebiotic in probiotic Yogurt.Conclusion: The study showed that prebiotics might be used for improving sensory and rheological properties of synbiotic Yogurt.

This research aimed to investigate the viability of probiotic bacteria (Lactobacillus acidophilus LA-5 and Bifidobacterium lactis BB-12) and Yogurt bacteria (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus) in Yogurt during the fermentation, immediately after fermentation and during refrigerated storage (21 d, 4oC). Also the biochemical characteristics of milk as affected by the commercial 4-strain mixed starter culture were investigated. Storage time affected the viability of all bacterial species. The concentration of lactic acid during the fermentation increased in parallel with the titrable acidity, and the concentration of acetic acid was proportional to the viability of Bifidobacterium lactis. The acetaldehyde level was decreased in the Yogurt from day 0 up to the end of the storage. Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus were multiplied considerably during the fermentation. Streptococcus thermophilus could maintain its viability to the highest level, but Lactobacillus delbrueckii ssp. bulgaricus lost its viability rapidly during the cold storage compared to Streptococcus thermophilus. The multiplication and viability of probiotic bacteria were also influenced by the associative strains and species of Yogurt organisms. Bifidobacteria counts were satisfactory. The loss of viability for bifidobacteria was gradual and steady during the storage, and they showed good stability during the storage as compared to Lactobacillus acidophilus.

In this research, the effect of kombucha on physicochemical (pH, acidity, syneresis, viscosity, vitamin C and ethanol) and overall acceptability of Yogurt samples were measured during 21 days of storage at 8oC. Thus the amounts of 5, 10 and 15% (V/V) of concentrate of kombucha layer grown up on black tea, with yoghurt starter, were inoculated to the milk containing 2.2% fat. Meanwhile, the Yogurt starter was applied for producing control sample. Fermentation in all samples was stopped when the pH reached 4.6. The results showed that during the storage, decrease of pH and increase of acidity were minor (p<0.01), and with raising the kombucha concentration, these changes were significantly less than control sample (p<0.01); syneresis in all samples (the same as control) increased while viscosity decreased (p<0.01) and increasing of kombucha concentration was caused increase of syneresis and decrease of viscosity (p<0.01); vitamin C decreased and ethanol increased very little (p<0.01) and as the kombucha concentration increased, the quantities of vitamin C and ethanol increased (p<0.01). Raising the kombucha concentration caused reduction of overall acceptability score in samples (p<0.01); and during storage, this score decreased (p<0.01) a little in comparison with that in control sample. After production and during storage, the best physicochemical and sensory properties was observed in sample containing Yogurt starter and 5% kombucha concentrate.

Background: Milk and fermented milk products have been known as foods with possible hypocholesterolemic effects. In this study we compared the effects of milk replacement with regular and probiotic Yogurt in normocholesterolemic (N) and hypercholesterolemic (H) subjects.Methods: Twenty eight subjects with total serum cholesterol 160-280 mg/dl were included. They did not consume Yogurt for 2 weeks after that 300 g/day of milk was added to their diet. Then, blood lipids were measured and they were randomly allocated to 2 groups to receive either 300g/day of ordinary Yogurt or probiotic Yogurt for 6 weeks as a substitution for milk. Blood lipid tests were repeated at the end of the study. Subjects in both groups were divided into these two subgroups according to their baseline blood cholesterol level: subgroup N (cholesterol<220mg/dl) and H (cholesterol³220mg/dl). Blood lipid changes were compared between these subgroups in each experimental group. Results: Total cholesterol and LDL-C levels reduced in the H as compared to N subgroup after regular Yogurt consumption instead of milk and the reduction of LDL-C was significant (P=0.033). The effect of milk replacement with probiotic Yogurt on total cholesterol and LDL-C reduction in H compared to N subgroup was higher than regular Yogurt consumption (P=0.028 and P=0.014 for total cholesterol and LDL-C respectively(.Conclusion: The higher the baseline blood cholesterol level, the more beneficial effects of milk replacement with Yogurt, especially probiotic Yogurt. So, it is suggested for hypercholesterolemic individuals to consume more Yogurt as the source of dairy products in their diet.

The aim of study was to produce a low-fat cacao containing probiotic Yogurt. For this reason a combination of probiotic bacteria, lactobacillus acidophilus and Bifidobacterium lactis (3% w/w) together with 0.8% cacao powder, 5% sugar as a well as 1.2% cacao powder with 7% sugar were used to produce a synbiotic Yogurt (0.5% and 1.5% fat). Populations of probiotics bacteria, physiochemical and sensory properties of the Yogurt samples were evaluated throughout the storage period (1, 7, 14, and 21 days). Result showed that cacao as prebiotic could significantly increase the viability of L. acidophilus (P<0.01), besides no significant difference was observed between the populations of B. lactis in the chocolate Yogurt and control samples. The highest quantity of the probiotic bacteria was observed at day 7, followed by a decrease in their number, however their populations remained above 7 log cfu/g. Moreover, pH value of the samples decreased over the time of storage, but pH value of the cacao-containing samples increased significantly (P<0.01). In comparison with the control group, no significant increase was recorded in the lipid content of the samples with cacao and sugar, meanwhile the amount of dry matter was higher than control samples (P<0.01). It could be concluded that apart from the prebiotic properties of cacao on L. acidophilus, it can improve the nutritional value of probiotic Yogurt and increases the calorie of the product. However for achieving better sensory properties, changes should be considered in the formulation.