INFLUENCE OF KERNEL DAMAGE ON CORN NUTRIENT COMPOSITION, DRY-MATTER LOSSES, AND PROCESSABILITY DURING ALKALINE COOKING

The nutrient losses of corn containing 0-30% damaged kernels that occu rred during alkaline cooking into tortillas were examined. Samples fro m different stages during processing were tested for chemical composit ion and protein fractionation. The most prevalent type of kernel damag e was mechanical, followed in decreasing order by molds, insects, heat , and rodent damage. Corn with higher content of damaged kernels was s usceptible to overcooking, resulting in cracked or fully open nixtamal kernels and sticky masa that were difficult to handle during processi ng. 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, da maged corn kernels were fully cooked into physically opened kernels wi th more nutrients being extracted into the water. About 15% of total s olids and 50% of both crude fiber and fat were lost during cooking of corn with 30% kernel damage. The greatest losses were consistently obs erved for albumins and globulins from both sound and damaged kernels a t all stages of cooking. Appropriate control of kernel damage level is required to improve yield of product with consistent quality. The sus ceptibility to overcooking of excessively damaged corn increases the c omplexity 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 treatmen t.