Removal of Tannins and Improvement of in Vitro Protein Digestibility of Sorghum Seeds by Soaking in Alkali

Soaking of sorghum seeds at 30° C in 0.05M sodium hydroxide and potassium hydroxide removed 75–85% of the tannins in 24 hr. Treatment at 100°C increased the rate of extraction and reduced the time required to leach 75–85% tannins from 24 hr to 20 min. Under similar conditions, 0.05M sodium carbonate removed 77% whereas soaking in distilled water removed only 30%. Dry matter loss due to the treatments with alkaline reagents ranged from 1.2–2.3%. Extraction of tannins in 0.05M alkaline solution at 100° C for 20 min improved in vitro protein digestibility of high tannin seeds 2˜5 fold as compared to untreated seeds.