Document Type : Research Article
Authors
Department of Food Science and Technology, Faculty of Food Industry, Bu-Ali Sina University, Hamedan, Iran
Abstract
Introduction
Balangu seed gum (BSG) is a hydrocolloid extracted from the seeds of Lallemantia royleana L.. This gum works as thickener and stablilizer in food products. This gum had high performance compared to some commercially available food grade gums. When this gum is mixed with water, it becomes thick (viscous fluid) and this gel-like substance becomes thin when stirred or shaken (pseudoplastic behavior) (Salehi & Inanloodoghouz, 2023). The term organic acid refers to organic compounds with acidic properties. The acidity of organic acids is associated with their carboxyl group and therefore they are called carboxylic acids. Organic acids can be classified according to the type of carbon chain (aliphatic, alicyclic, aromatic, and heterocyclic), their extent of saturation and substitution, and the number of carboxyl groups (mono-, di-, tri-carboxylic). Monocarboxylic acids like acetic acid are highly volatile liquids with a pungent taste. Malic and tartaric acids are also dicarboxylic acids that contain one and two hydroxyl groups, respectively. Citric acid is the best-known tricarboxylic acid with one hydroxyl group that is found in foods (Yildiz, 2010). The most abundant organic acid in citrus juice is citric acid. Also, citrus juices such as lemons, oranges, and grapefruits are a good source of ascorbic acid (Nour et al., 2010). pH is an important parameter that affects the rheological properties of hydrocolloid solutions. Addition of acid to an aqueous gum solution leads to changes in pH which affect the viscosity of this solution (Hayta et al., 2020). In this study the effect of four edible organic acids (ascorbic, citric, malic, and tartaric) at two concentrations (0.5, and 1 %) on the viscosity and rheological behavior of Balangu seed gum solution (0.2%, w/v) was investigated.
Material and Methods
In this research, organic acids including ascorbic, citric, malic, and tartaric were purchased in powder form (China) and dissolved in distilled water. Two concentrations of each acid, 0.5% and 1%, were prepared, and the distilled water was considered as the control (0% acid). The Balangu seed gum solutions were prepared by disolving the gum powder (0.20%, w/v) in distilled water containing different concentrations of ascorbic, citric, malic, and tartaric acids using a magnetic stirrer. The rheological parameters of Balangu seed gum dispersions were measured using a viscometer (Brookfield, DV2T, RV, USA) at 20°C. Power law, Bingham, Herschel-Bulkley, and Casson models are common ways of representing the behavior of several gum dispersions. In this research, these models were used to match the shear stress and shear rate results of the gum solutions containing edible organic acids. Differences between means were established using Duncan’s multiple range using SPSS (version 21).
Results and Discussion
The findings of this study showed that the apparent viscosity of Balangu seed gum solution reduced when the shear rate increased. Additionally, the apparent viscosity of the Balangu seed gum solution reduced as the organic acids concentration increased. The highest decrease in viscosity was related to solution containing 1% citric acid and the lowest was related to tartaric acid with a concentration of 0.5%. The rheological behavior of solutions was 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 Balangu seed gum solutions containing organic acids. The Power law model had a good performance with the highest correlation coefficient (>0.9406) and least sum of squared error (<0.0090) and root mean square error (<0.0275) for all samples. The consistency coefficient of the samples reduced as the acid percent was increased. Sample containing 1% citric acid had the lowest consistency coefficient and sample containing 0.5% malic acid had the highest consistency coefficient. The Power law model shows that a fluid with shear-thinning behavior has a value of flow behavior index less than 1 (Kumar et al., 2021). By adding acid to Balangu seed gum solution, the flow behavior index of most samples increased. The Bingham yield stress of all samples reduced when acids percent was increased. The dispersion containing 1% citric acid had the lowest Bingham yield stress and the sample containing 0.5% tartaric acid had the highest yield stress. The Bingham plastic viscosity of the samples reduced when acids percent was increased. The solution containing 0.5% ascorbic acid had the highest Bingham plastic viscosities (0.0038 Pa.s) and the sample containing 0.5% malic acid had the lowest plastic viscosities (0.0014 Pa.s). The results showed that when the ascorbic acid concentration was increased from 0.5% to 1%, the Casson plastic viscosities of the Balangu seed gum solution was decreased significantly from 0.054 Pa.s to 0.042 Pa.s (p<0.05).
Conclusion
The results of this study indicated that it is a mistake to use Balangu seed gum in food products containing high concentrations of citric acid, and this acid reduces the viscosity and consistency of the products containing this gum.
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