Solubilization of cashew gum from Anacardium Occidentale in aqueous medium

Authors: Kim, Sanghoon; Biswas, Atanu; Boddu, Veera; Hwang, Hong-Sik; Adkins, Jason

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2018
Publication Date: 7/14/2018
Citation: Kim, S., Biswas, A., Boddu, V.M., Hwang, H., Adkins, J.E. 2018. Solubilization of cashew gum from Anacardium Occidentale in aqueous medium. Carbohydrate Polymers. 199:205-209. https://doi.org/10.1016/j.carbpol.2018.07.022.
DOI: https://doi.org/10.1016/j.carbpol.2018.07.022

Interpretive Summary: Cashew gum is a naturally occurring biopolymer that has many applications, such as binders, sustained release tablets, multi-particulate systems for drug delivery, superabsorbent hydrogels, gelling agents, viscosity enhancers, surfactants, drying-aid agent, etc. Cashew gum is especially useful for the fabrication of drug-carrying particles. Although the physicochemical properties of cashew gum have been investigated by many research groups, there is a lack of understanding of its physicochemical properties, thus limiting its utilization. In this report, we show that the aggregates of cashew gum can be disintegrated by adjusting the acidity of the solution to neutral or basic. This allows chemical/physical treatment of cashew gum to be performed at the molecular level. These results will benefit scientists in academia investigating physicochemical properties of cashew gum and industries that process cashew gum products.

Technical Abstract: Although cashew gum (CG) is known to be soluble in water, the solubilized CG does not exist as individual molecules in its solution. Instead, CG molecules form aggregates resulting in a turbid solution. For better solubilization of CG in water, two types of approaches are attempted: thermal degradation and changing the pH of solution medium. The thermal degradation at high temperatures does not follow the same pattern as a similar polysaccharide, starch: instead of being thermally degraded to smaller molecules that are readily soluble in water, the aggregated CG molecules were not fully disintegrated to individual molecules even after the heating to 190°C. Size Exclusion Chromatography (SEC) shows that CG exists as entangled aggregates in aqueous solution at room temperature, and these aggregates disentangle in neutral or alkaline medium. Therefore, raising the pH of solution turns out to be a more efficient way to dissolve CG in water than thermal degradation. CG aggregates disintegrate only when the pH of its solution is adjusted to higher than 6.2. The peak MW of CG is measured to be 28 kDa. The lowest temperature that will initiate the thermal degradation and the temperature that induces full degradation of CG are estimated from the SEC chromatogram of heat-treated CG’s.