Effect of thermal popping treatment of Toluqueño creole popcorn maize (Zea mays L.): Changes in physical and structural properties

Objective: To assess the effect of popping thermal treatment on the physical and structural properties of Toluqueño creole popcorn maize (Zea mays L.) Design/methodology/approach: Toluqueño creole maize and commercial (Zea mays L.), as a control, were subjected to three popping treatments: hot oil, hot air and microwave. Moisture, popping yield, textural properties (hardness, gumminess, chewing), and structural features (size: area, perimeter) by image analysis were determined. Results: The results showed that the treatment by hot air in commercial maize presented the best pop yield, reaching a value of 71.88%, while the microwave treatment was the best for Toluqueño maize, with 12.93% of expansion yield, because its low moisture content (8.42 ± 0.29%). The best textural characteristics for both types of maize were obtained after applying the hot air treatment, resulting in soft, low rubbing and good chewing for all samples. The microstructural analysis in Toluqueño maize treated by microwave evidenced the presence of spherical starch granules, which was attributed to a low gelatinization degree. Also was possible to observe highest intergranular space, which was related to a less compactation grade and consequently less hardness in the raw grain (without expansion). Limitations on study/implications: High resolution and improved methodologies to observe the starch grain and components distribution could be result in a better description of the effect of thermal treatment in the maize grains. Findings/conclusions: The treatment by hot air was the best process to obtain popcorn for all samples, being the commercial maize who presented the best physical and structural features.