Processing and genetic effects on resistant starch in corn flakes

To evaluate the effects of processing and genetics on resistant starch content in corn flakes, a laboratory scale corn flaking procedure was developed at a batch size of 100 g grits. Cooking (0.1 MPa/121°C, 50 min), drying (100°C, 30 min), tempering (room temperature, 30 min) and toasting (200°C, 60 s) resulted in laboratory flakes that had similar color parameters (L, a and b values) but different RVA parameters (lower peak, trough and breakdown viscosities; higher final and setback viscosities) compared to commercial corn flakes. Seven corn hybrids were flaked with the developed procedure and resistant starch contents were determined at each processing stage for each hybrid. Cooking caused the largest decrease in resistant starch content; it remained at a similar level through subsequent processing stages of drying, flaking and toasting. Differences were observed in resistant starch content among hybrids at each processing stage. Therefore, both genetic background and processing affected corn resistant starch content. Hybrids with high resistant starch content in raw flaking grits resulted in high levels of resistant starch in the final toasted flakes. Since resistant starch content is correlated with amylose content, high amylose corn hybrids could be of use in the breakfast cereal industry for manufacture of corn flakes with higher nutritional quality, provided these hybrids have high grain yields and flaking grit yields for economic feasibility to corn producers and dry millers.