ISO Standards ISO 9648:1988 Sorghum — Determination of tannin content ISO 9648:1988 pdf download. Sorghum — Determination of tannin content. ISO 9648:1988 specifies a universal method for the determination of tannin content in sorghum grains. It is not specific for one single type of polyphenols. Its usefulness.... 01-24 Read More