Changes in soft-textured blue maize (Zea mays L.) by differential parboiling treatment

Pigmented maize varieties like blue maize are valued for their high nutraceutical content but are limited in their applications due to their soft, floury endosperm. This study evaluated the effects of parboiling, using autoclave and microwave methods, on kernel hardness and yield across 96 treatment combinations. Parboiling significantly increased endosperm hardness compared to the control (8 ± 3.4%). Autoclave treatments produced hardness levels ranging from 19% to 72%, with 42% moisture consistently yielding highly vitreous kernels regardless of cooking time or temperature. Intermediate hardness (19-63%) was achieved at 30-35% moisture, with greater values observed at 121 °C and 40 minutes. Microwave treatments generally resulted in lower hardness (0-35%), though 42% moisture produced hardness levels comparable to autoclave treatments (60-77%). Yields ranged from 5.5% to 85%. Microwave treatments achieved higher yields at low moisture (30%) and short cooking times (10 min), while autoclave treatments, especially at high moisture and longer times, showed an inverse relationship between hardness and yield. Cooking method, cooking settings, and time were the main factors influencing hardness, whereas yield was primarily affected by moisture content and cooking duration. The evaluation of parboiling as a post-harvest, non-genetic strategy to improve the processing quality of pigmented maize provides a practical framework for enhancing kernel hardness while maintaining acceptable yields, thereby facilitating the broader utilization of nutritionally rich blue maize in value-added cereal products.