Analyzing vegetable tannins: Incorporating ultraviolet spectroscopy and hide powder techniques

Abstract

The ultraviolet technique, known for its speed and cleanliness, proved to be highly advantageous in this study. It requires no reagents or pretreatment of the samples, making it a convenient method for analyzing different commercial vegetable tannins. By employing ultraviolet spectroscopy and Hide Powder techniques, valuable insights into the primary absorption bands were obtained, providing information about the chemical composition and structure of the extracts. In addition, specific absorptivity was determined, and the total polyphenols and tannin content of each extract were quantified using the filter and Folin Denis methods, respectively. The results showed that extracts of condensed tannins had the lowest values of specific absorptivity, while hydrolysable tannins exhibited the highest values. When analyzing the total polyphenols, condensed tannins, such as Acacia mearnsii and Azadirachta indica, displayed the highest percentages, with values of 73% and 60%, respectively. Hydrolysable tannins ranged from 51% to 36%. Furthermore, the evaluation of tanning percentage revealed that Acacia mearnsii and Azadirachta indica exhibited percentages around 40%, followed by Acacia nilotica ssp Tomentos pods, Acacia seyal var. seyal, and Pithecellobium dulce, with percentages of 29%, 25%, and 17%, respectively. These findings provide important information about the tanning potential of the different vegetable tannins studied.