Sudesh Shrestha New Road, Pokhara Tannin is a key component of a red wine. It comes from the skins, stems and seeds of the grapes and even from oak ageing. Tannin is a natural anti-oxidant and one of the key ingredients that can prevent red wine from spoiling.�Tannin can be tasted at the back of the tongue when you swirl the wine in your mouth. The puckering effect you feel is of tannin while drinking the red wine. Tannin tastes�herbaceous and is often described as astringent.