Wheat germ agglutinin is a biomarker of whole grain content in wheat flour and pasta

Background: When consumed as whole grain, wheat has a high nutrient density that contributes to a healthy diet. However, products labeled as whole wheat can still contain a substantial amount of non-whole grain wheat, leading to confusion for consumers trying to maximize their whole grain intake. A biomarker of whole grain is needed to reveal the whole grain status within wheat-based foods.Objective: Wheat germ agglutinin (WGA), a lectin found predominantly in the germ tissue of wheat kernels, was evaluated as a biomarker of whole grain in commercial wheat products. Methods: The levels of WGA within wheat flour and pasta were assessed by an immunoblot method and compared to a whole grain standard. WGA content was also compared to other biomarkers including starch, minerals, phytate, and total protein content.Results: WGA content tightly correlated with the percentage of whole grain in pre-made mixtures of whole wheat and refined (white) flours. Several commercial flours labeled as whole wheat were then tested for WGA content and found to contain up to 40% less WGA compared to a whole grain standard. Several commercial pasta products labeled as whole wheat were also tested for WGA content and found to contain up to 90% less WGA compared to a whole grain standard. The discrepancies in WGA content were unlikely due to wheat varietial differences alone, as the WGA content measured in common varieties used in domestic wheat flour production varied less than 25%. Other wheat constituents including starch, mineral, phytate, and total protein were less consistent and did not discriminate between the commercial whole wheat flours and pasta products. Conclusions: The WGA content within wheat flour and pasta correlated with the levels of whole grain and identified discrepancies when tested in commercial wheat products compared to a whole wheat standard. WGA is a unique biomarker that could help identify which wheat products have the greatest amount of whole grain wheat.