GC-IMS and GC-MS Analysis of Volatile Flavor Components of Fermented Corn Flour

Corn grits were used as raw materials, and the brewer’s yeasts Lactobacillus acidophilus, Bacillus subtilis, and Bacillus subtilis var. natto were used as fermenting agents to ferment corn to make corn flour in a single-strain and combination manner. The volatile flavor components of fermented corn flour were detected using gas-chromatography ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS) methods. A total of 68 flavor substances were detected using GC-IMS, including 12 aldehydes, 18 alcohols, 11 esters, 11 ketones, and 6 heterocycles. Graphical difference analysis revealed that all flavor substances of the corn flour changed after fermentation, and the content of alcohols, esters, and acids increased. Using GC-MS, 59 flavor volatile compounds were detected, comprising 13 aldehydes, 12 esters, 15 alcohols, 7 acids, 6 ketones, and 7 heterocyclic compounds. Among them, 29 key flavor substances—including 10 aldehydes (such as n-decanal), 5 alcohols, 2-nonanone, 2-heptanone, ethyl caproate, methyl formate, and ethyl butyrate—were identified as major contributors, with four acids serving as the primary flavor compounds of the fermented cornmeal. Aromatic analysis revealed that, compared with unfermented cornmeal, naturally fermented samples showed a 24.64% increase in fruity aroma. Fermentation with brewer’s yeast enhanced fruity and wine-like aromas by 30.05% and 85.05%, respectively. L. acidophilus fermentation increased fruity sweet and creamy honey aromas by 36.56% and 90.36%, respectively, whereas B. subtilis fermentation enhanced fruity, sweet, flower, and bitter almond notes by 18.05%, 15.59%, 38.68% and 38.02%, respectively. Mixed-strain fermentation led to increases of 53.53% and 48.08% in fruity sweet floral and grassy aromas, respectively. Overall, fermentation imparted a distinctive and enhanced flavor profile to the cornmeal.