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To date, there are no validated instrumental methods to independently determine the whole grain content of food. Thus, labeling claims for whole grains are difficult to police, and are ultimately dependent on the honesty of the food manufacturer – who may be tempted to “healthwash” a product, to make it seem healthy while still maintaining organoleptic properties similar to a non‐whole grain product. For both research and regulatory purposes, it would be useful to have a method for measuring whole grain intake by determining the amount of whole grain content in unknown samples.

There are no officially accepted methods for monitoring compliance to reported whole grain content or levels. The FDA in its whole grain health claim guidance directs that fibre content of at least 11% be used for this purpose, though this approach does not account for the wide range of dietary fibre contents in different cereal grains (e.g., wheat, used as a reference by the FDA as it is one of the most commonly consumed grains in the United States, has a dietary fibre content of around 10–11%, while brown rice has just 3–3.5% dietary fibre). A ratio of 10:1 carbohydrate to fibre has also been proposed as an index to help consumers choose foods with the highest whole grain content in foods⁽²²⁾ though this is essentially the same as the FDA proposal, and is not effective for foods with whole grain rice or corn/maize or foods with added fibre.

One simple method for regulators to monitor whether the whole grain content of foods matches that which is reported on packaging is to check the paper trail in relation to the making of that product – that is, following good manufacturing practice standards. In food manufacturing, there should be clear documentation detailing what ingredients have gone into making a batch of a product, including the weight. Thus, an audit of this documentation should reveal if the reported whole grain content accurately reflects what is in the product. This should work well where such record keeping is normal, but still requires a method that could highlight such products. Nor will it help in detecting the whole grain content in foods where the proportion of whole grains is not publicly available.

Independent methods are needed that can be used for both regulatory purposes and screening, including for food composition databases and work on whole grain intake. The major problem is finding a method that is able to differentiate between the addition of bran and whole grain flour. Measures such as that proposed by the USFDA that are based on dietary fibre are limited because of the inability of simple methods of measuring dietary fibre that distinguish between fibre from bran or other sources. Other more complex methods have been proposed for measuring the whole grain content of foods. These include the analysis of components that are derived from bran, germ and endosperm, and checking the relative ratios.⁽²³⁾ This has proven to be effective, but requires many different types of analyses so is expensive and too slow for screening or monitoring. Other more simple measures include the use of biomarker compounds such as the alkylresorcinols. These phenolic lipids are present as several homologues that differ between common wheat, durum wheat, rye, barley and quinoa, and represent a fingerprint that distinguishes between these cereals.^(24,25) However, alkylresorcinols are not present in other cereals, and they are mainly present in the bran fraction, so they cannot distinguish between whole grain flour or flour with added bran. In Table 5.1, it is possible to see the potential problems of using alkylresorcinols as markers of whole grain content, as several whole grain foods contain no alkylresorcinols, while wheat bran‐based breakfast cereal has the highest amount by some margin, even though for wheat‐ and rye‐based products they are strongly correlated to whole grain content.⁽²⁶⁾

The question of whether it is possible to develop a method that can distinguish between whole grain flour and flour with bran and germ added from another batch of flour, and is both rapid and cheap, remains open. That there are some methods available that are able to give some indication does at least help to reinforce measures such as auditing of good manufacturing practice documentation.