INDUSTRIAL PRODUCTION OF SOY‐ENRICHED TORTILLA FLOUR BY LIME COOKING OF WHOLE RAW CORN‐SOYBEAN MIXTURES

ABSTRACT Previous work has established that it is possible to enrich home‐prepared tortillas with soy proteins by lime cooking of whole raw corn‐soybean mixtures. Since tortillas are also extensively prepared in Mexico from limed corn flour, an investigation was carried out to determine if it were possible to enrich such flour by a similar procedure. The normal process for making tortilla flour was employed, except that In the lime cooking step, whole raw corn‐soybean mixtures containing 10% soybeans were used in place of pure corn. Protein quantity and quality of the enriched flour were found to be increased as follows: protein content, from 9.2 to 12.6%, an increase of 36%; protein efficiency ratio (PER) from 1.45 to 2.62 (casein PER = 3.40), an increase of 81%. Heat treatment of the enriched flour was found to be adequate by the urease method, and a trained panel could not significantly distinguish between tortillas prepared from either flour. Finally, rancidity was not detected organoleptically in a sample of flour stored at room temperature for 12 months. Considering present costs of corn and soybeans in Mexico, it was calculated that use of whole raw soybeans as an enriching agent for tortilla flour at a 10% level would raise the cost of the flour by 5%, while use of defatted soy flour for the same purpose, and at an equivalent protein level, would raise the cost of the flour by 40%.