Chemical Modifications and Applications of Cashew Byproducts - A Selective Review

Abstract

The cashew (Anacardium occidentale) is a tropical flowering tree that generates globally over 4 million metric tons of cashew nut a year. Although the cashew nut is the most well-known product, other byproducts can produce additional value, including cashew apple, cashew nutshell liquid, cardanol, and cashew gum. Over the years, a fair amount of R&D has been done on cashew byproducts in order to increase their value for different applications. In order to stimulate further interest in the use of these products, a selective review of the applications and chemical modifications of these byproducts has been made in this article. A particular emphasis has been made on the recent publications by the authors on cashew gum and cardanol derivatives to show how the use of specific polymer reactions (e.g., ene reaction, aminohydrin formation, amine-formaldehyde reaction, and polysaccharide ether and ester formation) and physical process (e.g., polymer blending, complex coacervation, microencapsulation, and electrospraying) can enhance the properties of these agro-based materials.

Extraction of Cardanol and its Applications

“…In particular, during the walnut extraction process, the shell that covers it is one of the main waste products. However, it is well-known that is rich in different metabolites, among them, the ones that have attracted the most attention are salicylic acid derivatives characterized by having an alkyl chain on the aromatic ring (Balgude and Sabnis, 2014; Cheng et al, 2022;Thiyagu et al, 2021). From the shell, it is possible to obtain an oily extract, dark in color, high viscosity, and complex composition, mainly urushiol and phenolic compounds.…”

On the Unique Morphology and Elastic Properties of Multi-Jet Electrospun Cashew Gum-Based Fiber Mats

“…Cashew gum, a complex water-soluble heteropolysaccharide, is extracted from the bark epithelial cells of Anacardium occidentale Linn trees, commonly known as the cashew trees [7]. These trees are mainly located in tropical and subtropical countries, even though their cultivation is, up to now, mostly aimed at the production of cashew nuts, while cashew gum was traditionally considered a low-value by-product [8]. Cashew gum can be obtained by spontaneous exudation, since it is synthesized in the epithelial cells and secreted, as a response to mechanical stimuli or attacks by pathogens, into ducts through the Anacardium occidentale tree bark [5,9], or it can be collected by means of incisions on the trunk and branches of the tree.…”