Effect of Xanthan Gum and Soluble Soybean Polysaccharide on Charactericties of Functional Flixweed (Descurainia Sophi L.) Syrup

Flixweed (Descurainia sophia L.) is an annual plant that found in various parts of the world including Iran. Flixweed seed and its syrup have been traditionally prescribed as a remedy for diarrhea, heatstroke, palpitation, upset stomach, impotence, intestinal inflammation, constipation, skin eruptions, laxative, and antipyretic since ancient times. Despite the unique pharmaceutical and nutritious advantages of this product, its production is faced with two major problems in the food industry; first, its use is not suitable for diabetics because of the high amounts of sugar in the syrup formulation. On the other hand, the sedimentation of flixweed seed syrup is one of the other common problems of this traditional drinking which restrict its commercial production. The aims of this study are the first to investigate the possibility of replacing the sugar with grape syrup as a natural sweetener to producing a functional syrup and secondly the possibility of stabilizing the flixweed syrup using soluble soybean polysaccharide and xanthan gum as natural hydrocolloids. For producing the functional flixweed syrup, the first step was to examine the replacing of grape syrup in various ratios (0:100, 10:90, 80:20, 70:30, 60:40, and 50:50) of sugar in the formulation of syrup as a sugar substitute. Then, in order to stabilize the flixweed syrup, the effect of various concentrations of xanthan gum (0. 1, 0. 2, and 0. 3 % w/v) and soluble soybean polysaccharide (1, 2, and 3 % w/v) was studied. For pasteurization, samples were heated in 80 C for 1 min, and then cooled to 7 C. Then, some properties of the syrups (Brix, pH, phase separation, colour, rheological and organoleptic properties) were compared together. Brix and pH were calculated using refractometer and pH meter, respectively. Stability of samples was investigated according to phase separation after thirty days storage of samples in the refrigerator. Color characteristics, including lightness (L*), Redness (a*), yellowness (b*), browning index (BI), and caramelization (Hue) were evaluated by means of Konica Minolta CR-400 apparatus. Rheological properties of the syrups were measured by Ultra DV3- LV Rheometer. Organoleptic features of samples containing color, flavor, odor, fluidity, mouth feel, and overall acceptability were evaluated using 10 trained penelists. The experiments were conducted in a completely randomized design and means were compared using Duncan method at p<0. 05. According to the results of this research, the optimal ratio of grape syrup to sugar was 40:60 as substitute of sugar in flixweed syrup. The best functional flixweed syrup included 5% seed, 6% sugar, and 4% grape syrup. Results revealed that the addition of xanthan gum and soluble soybean polysaccharide had no significant effect on pH and Brix of samples. In addition, soluble soybean polysaccharide had no effect on stability of syrups, while the xanthan increased the stability. The use of 0. 3% concentration of xanthan gum completely prevented the phase separation of syrup after thirty days' storage. The most appropriate model for the control syrup and samples containing soluble soybean polysaccharide was Newtonian model, and it was a pseudoplastic model for syrups including xanthan gum. The results of colorometric showed the pasteurization increased the lightness, redness, yellowness, caramelization and browning indices. As well as, the sensory characteristics of stabilized syrups were very similar to blank samples. Based on the findings of this study, that using grape syrup and xanthan gum can be produced the stabilized and functional Flixweed syrup including appreciate organoleptic features