Extrusion of quality protein maize (Zea mays L.) in combination with hard-to-cook bean (Phaseolus vulgaris L.)

Maize has high carbohydrate content, but very low protein content and low levels of lysine and tryptophan. These deficiencies have been addressed through development of maize hybrids known as quality protein maize (QPM) in which lysine and tryptophan levels are twice that of normal maize. During storage under high humidity (> 75%) and temperature (> 30 °C) beans develop the hardening process, which changes its character-istics in a negative way, mainly by increasing cooking time, these features greatly reduce their commercial value. Mixing of QPM and hard-to-cook beans (HTC) can be used to balance the amino acid profile of the resulting product without notably affecting sensory acceptance. Processing by extrusion is of particular interest because it is widely used to incorporate legume seeds into cereals for production of precooked flours, infant food and expanded snacks. These extruded products offer advantages in terms of their sensory characteristics and nutritional properties. Extruded maize products on the market usually provide a 6% of protein, the combination of QPM with HTC yields a product with a higher protein intake (15%), with a better balance of amino acids and appropriate sensory characteristics. Thus extruded products obtained have the potential to be commercially produced in addition to having a better nutritional intake than snack type products on the market.