Nixtamalization is an alkaline cooking process known to lower aflatoxin B1 (AFB1) in maize, yet reported efficacy varies (28-100% reduction). Thus, existing data are not sufficient to inform nixtamalization practices in specific local contexts. To investigate this, we conducted a controlled lab study using AFB1-contaminated Guatemalan maize to evaluate the effect of current rural Guatemalan cooking practices on the AFB1 concentration. We evaluated nine conditions varying calcium hydroxide concen