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Chemistry of Cocoa Flavanols

Defining Cocoa Flavanols
As a subclass of flavonoids, flavanols are found in a variety of plants. The unique, specific mixture of flavanols found in cocoa is collectively referred to as "cocoa flavanols." The term refers to the sum of the simple (monomeric) flavanols, including epicatechin, and to a lesser extent, catechin, as well as the linked (oligomeric) flavanols, known as procyanidins.

Cocoa Flavanol Stereoisomers
There are four forms of flavanols that are found in cocoa flavanols. These forms, called stereoisomers, are both naturally occurring and can be transformed from one form to another through food processing. Other foods have different types and mixtures of these isomers. The type and mixture of these stereoisomers found in cocoa beans are known as:
(+)-epicatechin
(-)-epicatechin (pronounced "minus epicatechin")
(+)-catechin
(-)-catechin

Cocoa is particularly rich in (-)-epicatechin, and research demonstrates that (-)-epicatechin is highly bioavailable (readily absorbed) as compared to the other isomers. Research to date has also indicated that the positive cardiovascular and blood vessel results shown have been attributed to (-)-epicatechin.

In addition to the flavanols, the term “cocoa flavanols” also refers to the linked (oligomeric) flavanols, called procyanidins. Procyanidins vary in size, and are typically referred to by the number of flavanols linked. For example, two linked flavanols are dimers, three linked flavanols are trimers, and so on. The term cocoa flavanols represents the collective sum of monomer flavanols and procyanidins up to and including decamers (ten linked flavanols).

How Traditional Food Processing Impacts Amount of Flavanols and Stereoisomers in Cocoa
Traditionally, the manufacture of cocoa products (e.g. cocoa powder, chocolate) involves steps such as fermentation, alkalization (dutching), and roasting, which can destroy or change the form of flavanols. A significant amount of the naturally present (-)-epicatechin is transformed (epimerized) during traditional food processing into (-)-catechin, a flavanol that is only a very minor component in unprocessed cocoa. Previous research has shown that (-)-epicatechin is the most absorbed by the body, almost six times more than (-)-catechin.

How Cocoa Flavanols are Measured
Until now, there has been no standard, validated approach for the analysis of these flavanol compounds in foods. In August 2013, Mars, Incorporated, received the Multi-Laboratory Study of the Year award from AOAC International for successfully completing a multi-laboratory validation of a method for analyzing flavanols and procyanidins in cocoa-based products. With a validated standard method in place, the scientific community and industry will be able to measure flavanol content in a consistent way, creating a uniform language for communicating with each other and with the public. For consumers, this means more consistent package labels that make it easier to make informed decisions.