Isn't "in" redundant here? I think it should be removed. What do you think?
42) Iron deficiency and its more serious consequence, anemia, are especially common among people who do not eat meat or cannot afford it, and who therefore survive on grains. Wheat and maize are often enriched with iron. But rice has proved hard to enrich without negatively affecting its appearance or flavor. Diego Moretti at Wageningen University and his colleagues tried using ‘fake’ rice made out of iron-enriched rice-flour dough and shaped by machine into grains. They mixed grains of enriched fake rice in with real rice and served it to iron-deficient school children in India.
You could argue successfully that it is redundant but that does not make it wrong. It is very natural. Language is not logic.