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Influence of Kernel Damage on Corn Nutrient Composition, Dry Matter Losses, and Processability During Alkaline Cooking

¹Cereal Quality Lab., Soil & Crop Sciences Dept., Texas A&M University, College Station, TX 77843-2474. Corresponding author. E-mail: H-almeida@tamu.edu Phone: 409/845-2967. Fax: 409/845-0456. ²Div. de Estudios de Graduados e Investigación, Instituto Tecnológico de Mérida, Km. 5 Carretera Mérida-Progreso. Mérida, Yucatán 97118. México. ³Centro de Investigación en Alimentación y Desarrollo, A.C., Km. 0.6 Carretera A La Victoria. Apdo. Postal 1735. Hermosillo, Sonora 83000. México.

The nutrient losses of corn containing 0–30% damaged kernels that occurred during alkaline cooking into tortillas were examined. Samples from different stages during processing were tested for chemical composition and protein fractionation. The most prevalent type of kernel damage was mechanical, followed in decreasing order by molds, insects, heat, and rodent damage. Corn with higher content of damaged kernels was susceptible to overcooking, resulting in cracked or fully open nixtamal kernels and sticky masa that were difficult to handle during processing. Nutrient losses increased with increasing levels of kernel damage. Most nutrient losses from sound corn kernels occurred during washing as the pericarp and attached solids were removed. During simmering, damaged corn kernels were fully cooked into physically opened kernels with more nutrients being extracted into the water. About 15% of total solids and 50% of both crude fiber and fat were lost during cooking of corn with 30% kernel damage. The greatest losses were consistently observed for albumins and globulins from both sound and damaged kernels at all stages of cooking. Appropriate control of kernel damage level is required to improve yield of product with consistent quality. The susceptibility to overcooking of excessively damaged corn increases the complexity to consistently meet product quality specifications. Excess dry matter losses in the cooking liquor can significantly increase the risk of environmental contamination and cost of sewage water treatment.