Effects of thermal processes on physical, chemical, and nutraceutical properties of popcorn and popped sorghum

Abstract

Corn and sorghum grains are a significant source of nutrition and phytochemical compounds. When those grains are popped with thermal methods, they represent a healthy alternative to the snacks available on the market, with a compound annual growth rate of 11.10%. Producing popped kernels as a snack involves different methods and technologies such as microwave, wet cooking, and recently hot air; those methods could induce changes in their physical and nutritional properties. However, there are no reports on the effect of different cooking methods on these non-conventional cereals. Therefore, the objective of the present study was to evaluate the effects on physical, chemical, and nutraceutical properties of six different corn cultivars (Z. mays everta; blue, purple, red A, red B, black, and yellow) and two different cultivars of sorghum (Sorghum bicolor L; red, and yellow) popped by microwave, wet cooking, and hot air. To evaluate physical and chemical analyses official methods were used. The nutraceutical profile included anthocyanins, bound, free, and total phenol. Chemical and nutraceutical analyses were performed before and after thermal processes. The findings elucidate that sorghum grains had the smallest dimensions and 1000-grains weight and higher flotation index with an average of 25.75 g and 14.49 %, respectively, compared with the results obtained from corn kernels 133.66 g of 1000-grains weight and 1.6% of flotation index. Variations among 1000-grain weights, flotation index, and dimensions impacted the yield and expansion volume of the popped kernels, obtaining the highest yield for corn at 91.15% and sorghum at 51.78% when they were popped with hot air. Changes were observed in the chemical and nutraceutical properties of corn and sorghum kernels after being processed by thermal methods. The percentages of protein and starches (total and digestible) increased around 2% and 23% in popped corn and 7% and 27% in sorghum, respectively. Total phenolic compounds and anthocyanins decreased after popping, averaging 43.26% and 42.91% in popped corn and 31.74% and 49.00% in sorghum. These results indicate that the nutraceutical properties of popped corn and sorghum are less affected when they are popped by the hot air method. The black corn had the highest physical, chemical, and nutraceutical parameters when treated using hot air, followed by sorghum varieties. Therefore, new lines of research can be developed based on these findings to produce snacks with high nutritional content.