Determination of the bacterial sourced exopolysaccarides on viscosity

Polysaccharides consists of heterogenous carbhydrate groups have high polimerization ability. They have been using for texture improvement, holding water and stabilization of emulsion for a long time. Polysaccharides can be obtained from different sources like plant, algae, bacteria and fungi. Exopolysaccharides (EPS) is one of these polysaccharides. Microbial EPSs have important role in different industries because of their physicochemical and rheological properties. And they can be isolated easier than other polysaccharides. Due to this easier isolation, studies about microbial EPSs are increasing nowadays. Lactic acid bacteria (LAB), gram positive, can metabolize the lactose and mostly generate lactic acid. These bacteria can also fermentate. LAB are usually immobile are have similar physiological properties but different morphological properties like in the form of coke or rods. LAB are seperated in two family, Streptococcaceae and Lactobacillaceae. LAB can use in food industry as an emulgator or thickener. They can also produce EPS in two forms, capsule form or be secreted. They provide human health as antitumor, antiulcer, antiviral and antioxidant. Bacterial EPSs s one of the LAB's metabolits. They provide a connection between the the substrate and probiotics. They are using in cosmetic and food industry due to the variation in the composition and higher molecular weight. They are using in biomedical, bio-pharmaceuticals and cosmetic industry due to their antitumor, immunostimulating, anticoagulant, hypoglycemic and antioxidant properties. Bacterial EPSs are divided into two clasess, homopolysaccharide and heteropolysaccharide. EPSs, produced by LAB, improve the rheological properties, texture, mouthfeel, taste and stability of the fermented products. EPSs are using in fermented milk products to avoid syneresis and improve the texture and viscosity. Probitioc properties of the LAB are increased by EPS in artifical environment. Antiviral property of the EPSs depends on the sulphate groups in EPS molecular. Antiviral property increases when sulphate groups increases however viscosity decreases. The aim of this study to investigate the rheological properties of the wheat water and distilled water after adding bacterial sourced EPSs isolated from soy water. In this study, LAB have higher capability to produce EPS, according to the study lights in 2014, are selected to show the effects of EPSs. EPS production was provided with 8 different bacteria's specfic strains (Lactobacillus coryniformis, Lactobacillus paracasei, Lactococcus lactis, Pediococcus parvulus, Streptococcus macedonicus, Weissella confusa and Lactobacillus brevis) into soy water before this study and these EPSs were isolated from soy water. pH values of the wheat water and distilled water are fixed to 6.0 at room temperature before adding the EPSs in the samples to minimize the variables. 10 ml wheat water and distilled water are placed in test tubes and they are heated in a water bath for 15 minutes. At the same time, control samples are prepared and heated in water bath. After 10 minutes heating, 0,1 g EPSs from different strains are added in each samples and vortex mixer is used to obtain a homogenous mixture. These samples are heated in water bath until dissolved. After the samples reach the room temperature, Parallel Plate Sensor in RheoStress equipment is used to measure the viscosity. Appearance viscosity is measured at 25oC, in 120 seconds and different shear rates from 0.01 s-1 to 300 s-1. Apparent viscosity values are calculated by Ostwald-de Waele Model and compared with control samples. For both samples, wheat water and distilled water, have been observed that the viscosity of the mixture prepared by adding EPS is higher than the control samples. It was found to have the lowest viscosity value of the control samples compared with wheat water samples. The wheat water samples added to EPSs have higher viscosity value. The mixture which is added EPS isolated from L. coryniformis C55 strain in wheat water has the highest viscosity value. It was also found to have the lowest viscosity value of the distilled water, similar with wheat water samples. The mixture added EPS isolated from L. lactis F39 strain in distilled water has the highest viscosity value. The viscosity behavior of the samples which is added EPS is compared with the control samples for both wheat water and distilled water. All graphics show that the viscosity of the control sample is lower than the other samples for each samples added EPS. All rheological behaviors for all samples are also shown in one graph to compare all strains and control samples. The viscosity results are investigated by one group t-test to understand the difference between results is significantly important or not. For wheat water samples, the p value is calculated as 0, 000000635 (p<0,001) and for distilled water samples the value is 0,00000819 (p<0,001). These p values show that the differences between the results are statistically important. The difference between two samples' group results, wheat water and distilled water, is calculated by two independent groups t-test. The p value is 0,330 (p>0,05). It shows that the difference between two groups are not statistically important. Further studies should be performed to investigate the differences between two sample groups, wheat water and distilled water, exactly. The correlation between two groups' results, wheat water and distilled water, is calculated and the p value is obtained as 0,643 (p>0,05). The linear relationship between two groups' results cannot be commented because the calculated p value is higher than 0,05. Viscosity is an important parameter in foods because it affects the sensory properties of foods such as mouthfeel and aroma dissolution. In this study, samples demonstrated as a pseudoplastic property, reduction of the viscosity with increasing shear rate. This pseudoplastic property facilitates the use in the processes of these samples. The viscosity results for both wheat water and distilled water compared with the control samples are statistically significant different. This study is compared with the other studies done in 2005 and 2016 and similar results have observed. These studies are usually performed with fermented foods and non-newtonian flow behavior was observed all these stuedies in 2005 and 2016. In these studies, the pH effects on the EPS production was also investigated and generally, pH value between 4 and 7 gives the best results to produce EPS and increase the viscosity in food industry. As a result, the usage of the microbial meatabolites to improve the food characteristics in food industry is gaining importance day by day and studies about microbial metabolits like EPS are increasing. According to the results of these studies, the areas of the microbial metabolites are expanded. This study shows that the bacterial sourced EPSs can be used in food industry to improve the texture and mouthfeel and thick. It can be also used in cosmetic and biomedical industry apart from food industry. For this aim, further studies should be performed to see the effects of the microbial metabolits.