Synergistic effect of locust bean and xanthan gum on viability of probiotic bacteria and water holding capacity of synbiotic yogurt from camel milk

Introduction: In recent decays, consumers have more information about foods. Vegetables, crops and other natural food with high nutritional value replace hazardous substances. In this study, the effects of locust bean gum and xanthan gum with β-glucan were investigated in camel synbiotic yogurt functional. Locust bean gum (LBG) has about 88% of galactose and mannose, 4% other polysaccharides, 6% protein, 1% cellulose and 1% the ashes (Nasirpour, 2013; Hansen, 1993).Xanthan gum is an extracellular polysaccharide produced by Compestris Xanthomonas in aerobic fermentation process. Xanthan reactions synergies with guar and LBG, so the low concentrations in the presence of LBG viscosity increase (Ramirez-Figueroa et al., 2002).In this study, the oats β-glucan inoculated with probiotic bacteria to camel milk for production of functional synbiotic yogurt was employed. The camel milk has high nutritional value such as insulin-like substance, less lactose, immuno-globulins and lactoferrin, antioxidants and antimicrobial agents and other nutrients (ladjevardi et al., 2015; Niasari Naslaji et al., 2011). Synbiotic dairy product made from combinations of probiotic bacteria with prebiotics agent (β-glucan). About 108- 107 cfu/mL of live bacteria should be in the final products (Faraj et al., 2012). β-glucan is an indigestible carbohydrate complicated (Theuwissen & Mensink, 2008) with very high nutritional properties, including improved intestinal activity (fibers), lowering uric acid blood, stimulating the immune system (Xue et al., 2013; Chao et al., 2013). Materials and Methods: At first, camel milk (from Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Iran) was standardized by centrifugation (Universal 320, Hettich, Tuttlingen, Germany) to 1.9% fat content. Then xanthan gum and locust bean gum (1:1) were added in three level 0.1, 0.2 and 0.3%. β-glucan (extracted from oats as described by Moura et al. (2011() in 1.5, 2 and 2.5% levels was added to milk. Camel milk was homogenized with ultra-turrax blender (T25, IKA, Staufen, Germany) in speed 9000 r.p.m. Then, the milk sample was pasteurized for 15 min at 75±1 °C. Samples were prepared by adding yogurt starter culture (1.5%) containing probiotic microorganisms (ABY1, Cristian Hansen, Hørsholm, Denmark) at 42 °C. The mixtures were redistributed into 50 mL sterile plastic cups, incubated at 42 °C until their pH decreased to 4.6, they cooled and stored at 4±1 °C ( Mazloomi et al. 2011). Determination of water-holding Capacity (WHC)5 g of yogurt was centrifuged (Mikro 220R, Hettich, Tuttlingen, Germany) at 4500 r.p.m. for 30 min at 10°C. After centrifugation, the supernatant was removed and the pellet was collected and weighed. Microbial Analyses1 g of yogurt with 9 mL of normal saline (a solution of 0.9 % (w/v) NaCl ( Merck, Darmstadt, Germany)) was mixed and diluted to a concentration of 106 and 107, and then 1 mL of each dilution was repeated in 2 plate containing the MRS-Agar (Merck, Darmstadt, Germany) with 0.15% Bovin-Bile (Sigma-Aldrich, Louis, MO, USA). Bacteria were counted by the pour plate technique. The plates in duplicates were incubated anaerobically at 37 °C for 72 h, after this period, colonies were counted (Mishra and Mishra 2012). Statistical AnalysisThe response surface methodology (RSM) and ANOVA (p<0.05) were used for data analysis using Design Expert 8 (Version 8.0.7.1, Minneapolis, MN, U.S.A) software. The experiment was designed according to central composite design (CCD). All experiments and measurements were conducted in triplicate, mean value ±sd are reported.  Result and discussionWater-Holding Capacity (WHC)Changes of xanthan gum, LBG, β-glucan and time storage have a significant effect on the WHC. Increasing the percentage of LBG, xanthan gum and the percentage of β-glucan significantly increased the WHC. Time storage reduced the WHC similar results of Ladjevardi et al. (2015) and Sahan et al. (2008).According ANOVA table, the products had maximum water holding capacity at the highest percentage of LBG and xanthan gum. The percentage of xanthan gum and β-glucan increased water holding capacity. These factors (LBG and xanthan gum, xanthan gum and β-glucan) have a synergistic effect on each other mutually.Xanthan gum and LBG showed interaction effect with time storage on changes in WHC including maximum water retention in the sample tissue, the high percentage of gums and the early days of production. Viability of probiotic bacteriaViability of probiotic bacteria significantly increased when used from high percentage of β-glucan (as a prebiotic agent) in synbiotic yogurt. This change was related to increasing food for probiotic bacteria (Kearney et al., 2011). According to the results mentioned a good environment for the growth and activity of the microorganisms (ladjevardi et al., 2015). The unfavorable conditions in production of synbiotic yogurt, was time duration. During storage, the number of probiotic bacteria that are present in the product is reduced Xanthan gum and LBG have no significant effect on viability of probiotic bacteriaXanthan gum and time storage have interaction effect on the viability of probiotics bacteria. As expected, the best conditions for probiotic bacteria to maintain a high percentage of xanthan gum was at the early days of the sample production ((Norton and Lacroix, 1990; Sanderson, 1990).According to the results, it was found that gums such as xanthan gum and LBG showed similar results to those of El-Salamt et al. (1996) and Hematyar et al. (2012) and had adverse influence on the growth and activity of beneficial bacteria.