Influence of organic acids on the viscosity and rheological behavior of guar gum solution
Fakhreddin Salehi, Kimia Samary, Maryam Tashakori
Abstract
The present study aims to determine the influence of four edible organic acids (ascorbic, citric, malic, and tartaric) at two concentrations (0.5, and 1 %) on the viscosity and rheological behavior of guar gum dispersion (0.2%, w/v). The finding of this study revealed that the apparent viscosity of guar gum dispersions reduced when the shear rate increased. Additionally, the apparent viscosity of the guar gum dispersions reduced as the organic acids concentration increased from 0 to 1 %. The highest decrease in viscosity was related to 1% ascorbic acid and the lowest was related to 0.5% malic acid. The rheological behavior of dispersions were successfully modeled using Power law, Bingham, Herschel-Bulkley, and Casson models, and the Power law model was the best one for describing the behavior of guar gum dispersions containing organic acids. The Power law model showed good performance with the maximum r-value (mean=0.9988) and least sum of squared error (SSE) values (mean=0.0021) and root mean square error (RMSE) values (mean=0.0119) for all samples. The consistency coefficient (k-value) values of the samples (Power law and Herschel-Bulkley models) reduced as the acid percent was increased. The sample containing 1% tartaric acid had the lowest k-value and the sample containing 0.5% ascorbic acid had the highest k-value. The flow behavior index (n-value) (Power law and Herschel-Bulkley models) of the samples increased when the acid percent was increased. In summary, the use of guar gum in food products containing high concentrations of tartaric and ascorbic acids is not recommended.