Tannins constitute a heterogeneous group of polyphenolic compounds, present in a considerable number of vegetable foods. The term tannin is derived from the properties of these compounds to interact and precipitate macromolecules, such as proteins, make them able to tan animal leather. Subsequently a general definition for tannins emerged, referring them as high molecular weight polyphenols that precipitate protein from solution. The first chapter of this book begins with a discussion on the adsorbent biopolymers from tannin extracts for water treatment. The second chapter presents the influences of sensory and psychosocial factors on the intake of tannin-rich foods and beverages. Chapter three investigates condensed tannins derived from grapes and their antioxidant and antimicrobial activity. Chapter four provides a review of the latest research in the extraction of tannins from grapes and how tannin structure can influence wine astringency. The tannin chemistry diversity and its occurrence in ruminant diets, as well as its beneficial and adverse effects on ruminants will be briefly reviewed in chapter five, and aspects related to oral cavity physiology, saliva production/composition and postingestive effects will be also be referred. The final chapter evaluates milk composition of crossbred dairy goats fed Tifton 85 grass replaced by flemingia.