Scientists at the Institute Of Food Research in Norwich analyzed that non extractable polyphenol content in fruits is up to five times higher than extractable compounds.
Polyphenol content in fruits usually refers to extractable polyphenols. These polyphenols need to be treated with acid to extract them from cell walls of fruit.
Sara Arranz from the Spanish Council for Scientific Research (CSIC) in Madrid says that if non extractable polyphenols are not considered, the levels of beneficial polyphenols like ellagic acid, proanthocyanidins and catechin are significantly underestimated.
Non-extractable polyphenols, which are usually not considered in nutritional studies, are a major part of bioactive compunds in diet. These polyphenols are major elements in human diet and to consider them in nutritional studies might be useful for understanding effects of fruits and other plant foods in health.
Source: Institute Of Food Research