Mesquite bean harvest yields flour for sweets

For the last four years, UA students and volunteers have been harvesting mesquite pods on campus as a project with Campus Sustainability. While the arboretum proudly houses 12 types of mesquites, including 3 hybirds, the pods of each species vary in suitibilty for flour production. When ground, the right pods transform into a nutritious and gluten-free flour that is widely proclaimed as a "super food". The flour brings out the best in sweets like brownies, pancakes, and cookies, but it can be used in a wide variety of foods. 


The only catch is aflatoxin, a carcinogen produced by a fungus that can grow on moist mesquite pods touching the soil. As it happens, mesquite pods mature during the height of summer – just when the annual monsoon tends to bring half a year's rainfall in two months. For this reason, the UA carefully monitors and tests the pods to make sure no aflatoxin gets into the flour.


Harvesters have been experimenting with different types of gleaning, including active handpicking and passive capturing in nets. The painstaking method of hand-picking the pods uses rakes to pull high branches into reach. This ensures the mesquite pods never touch the soil.


This past summer, students worked to develop a passive system that used nets to catch the pods as they fell naturally from the trees. Unfortunately, the pods generally slipped through the nets. Thus in the short term, harvesters are leaning toward hand-harvesting as the way to go.


The mesquite harvesting project collaborates with another lab by providing discarded pods. These researchers, who worked on growing many types of edible mushrooms, have found that some mushrooms and actually break down aflatoxin. Ongoing research considers how the detoxification process occurs.