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A Rapid and Eco-Friendly Method for Determination of Hydrolysable Tannins and Its Application to Honey Samples

Catelani, Tiago Augusto, Bittar, Dayana Borges, Pezza, Leonardo, Pezza, Helena Redigolo
Food analytical methods 2016 v.9 no.9 pp. 2552-2559
acetates, experimental design, honey, pH, reflectance spectroscopy, spectrophotometers, tannins, wastes
This paper describes the development of a rapid and clean method for the determination of hydrolysable tannins in honey samples, focusing on an easy and green sample pretreatment and low generation of waste. The proposed method is based on the reaction between KIO₃ and hydrolysable tannin compounds in acetate buffer medium (pH 4.75), with formation of a colored product measured at 525 nm. The analytical conditions were optimized using experimental design (central composite design). The linear range obtained was 40.0–740 mg L⁻¹ (r = 0.998), and the detection (LOD) and quantification (LOQ) limits were 12.2 and 40.8 mg L⁻¹, respectively. Acetate buffer was used to ensure formation of the colored product obtained by reaction between the chromogenic reagent and the analyte. The method showed good results when applied to honey samples, with recoveries in the range of 78.3–96.1 %, and the use of diffuse reflectance spectroscopy coupled with spot test analysis provided low reagent consumption and minimized waste generation. The results obtained with the proposed method were confirmed by a spectrophotometric method.