The amount and type of tannins synthesized by plants varies considerably depending on plant species, cultivars, tissues, stage of development, and environmental conditions. Therefore, the study of the nutritional effects of tannins on animals requires quantification of the tannins present in a particular diet. . Due to the complexity of tannins, several methods have been developed for their quantification. None of them, however, is completely satisfactory. If freeze drying is too expensive or the equipment is not available, freezing without thawing of the sample before extraction is suggested.
Acetone inhibits tannin-protein interaction.
This is a limitation in protein precipitation assays. This unextractable fraction cannot be ignored because of its nutritional effects. Sample purification and isolation Tannins need to be purified from low molecular weight phenolics and pigments that are present in crude plants extracts. Purification is essential for the preparation of suitable standards. Purification of large quantities of tannins can be done by taking advantage of their absorption by Sephadex LH-20.