Análise quantitativa e caracterização de taninos extraídos da casca do cajueiro (Anacardium occidentale) para aplicações em adesivos naturais

Abstract

In the search for renewable alternatives for the synthesis of adhesives, tannins have been a promising alternative, since extractions from tree bark have been widely used to replace petrochemical products, such as adhesives for wood panels. Anacardium occidentale, a species of cashew tree native to Northeastern Brazil, is traditionally used as food through its pseudofruit, while its extracts have therapeutic applications. This study aims to quantify the yield of condensed tannins from cashew bark and evaluate its applicability in natural adhesives for gluing laminated panels. Tannin extractions were performed in water and in sodium sulfite solutions (1%, 2%, 3% and 4%) for comparison. The barks were also analyzed for their anatomy and chemical composition (extractives, lignin, ash and suberin), as well as through the analysis of phenolic compounds and Fourier Transform Infrared Spectroscopy (FTIR). The results indicated that extraction with 3% sodium sulfite provided tannins with a Stiasny index of 73.35%, demonstrating greater purity compared to the other treatments. FTIR analysis confirmed the polyphenolic structure of the condensed tannins. Therefore, we conclude that cashew bark tannins are promising for use in natural adhesives, with emphasis on the effectiveness of sulfitation in removing these tannins.