Fourier Transform Mid-Infrared (FTIR) Spectroscopy to Identify Tannin Compounds in The Panicle of Sorghum Mutant Lines

Abstract

G5 and G8 are two sorghum mutant lines projected as sorghum varieties for ruminant’s feed. However, most of the sorghum panicles contains phenolic compounds, especially in the form of condensed tannins. The objective of this research was to investigate the phenolic and tannin compounds from the panicles of two sorghum mutant lines. The second objective was to identify tannin content by Fourier Transform Mid-Infrared (FTIR) Spectroscopy in the sorghum panicles. The two mutant lines were compared with Pahat variety. This research was arranged into a randomized complete block design with two factors. The first factor was the sorghum variety/mutant lines, whereas the second factor was the generative phase of harvesting time (flowering, soft dough and hard dough). The results showed that the panicles of G5 sorghum contained the lowest total phenol compounds (P<0.01). The average mean of G5 and G8 mutant lines produced lower total tannin content (27.3 and 18.2%, respectively) than Pahat variety (P<0.01). Generally, total phenol and total tannin in all variety/mutant lines increased with the increasing maturity stage (P<0.01). All the spectra of the sorghum panicle samples in different harvesting age investigated shared certain special similarities. A band due to alkane medium (C-H) stretch was observed at 2937-2854 cm−1. At 1521-1514 and 1446-1408 cm−1, a band due to the C-C aromatic compounds was observed. Based on those findings, it can be concluded that G5 and G8 mutant lines produced less total phenol and total tannin contents than Pahat variety. Meanwhile, FTIR could be used to describe the profile of tannin compounds qualitatively.