Cold water processing by soaking, cooking and washing has been used for hundreds of years to produce debittered lupine in the Andean region. The process of debittering lupine (Lupinus mutabilis Sweet) was investigated at semi-industrial village-scale and laboratory scale in Ecuador. The process took 5.7±1.0 days, removed 94.9% of the total alkaloids, used water at almost 62 times the weight of the raw dry and bitter lupine, and caused a 22% loss of total solids, principally fat, minerals and carbohydrates. During the debittering process the microbiological quality deteriorated. Mathematical modeling based on Fickian diffusion suggested that the diffusion coefficient of alkaloids would be expected to be between 10-10 and 10-11m2/s because the lupine endosperm is a polymer matrix whose properties change during processing. Of the process operations, cooking was the most efficient at removing alkaloids both in terms of time and water used, followed by soaking and washing.