Effects of Blanching Followed by Spray Drying on Volatile Flavor Compounds in Sweet Corn

The effects of blanching followed by spray drying on volatile flavor compounds in sweet corn were investigated. The volatile flavor compounds in fresh, blanched and spray-dried sweet corn were analyzed by headspace solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). The qualitative analysis was carried out by comparison of the spectra for the chromatogram peaks with those in the NIST14 database library and comparison of retention index (RI), and the quantitative analysis by an internal standard method. Gas chromatography-olfactometry (GC-O) was used to analyze the composition of odor-active compounds and overall flavor profiles. The results showed that a total of 58 volatile flavor compounds were detected in fresh, blanched and spray-dried samples. Blanching and spray drying had significant effects on the types and contents of volatile flavor compounds in sweet corn. After blanching treatment, the contents of ketones, aromatic compounds, terpenes and aldehydes were decreased, and the total content of volatile flavor compounds decreased by 36.60%. After spray drying, the total content of volatile flavor compounds was increased by 19.21 and 30.30 times compared with those of fresh and blanched sweet corn, respectively. Among them, the contents of aldehydes, ketones, alcohols and heterocyclic compounds were increased, and new substances such as dimethyl thioether and 2-acetyl-1-pyrroline were detected. Principal component analysis (PCA) showed that the decreases in the contents of 2-nonenal (E), 3-ethyl-2-methyl-1,3-hexadiene, octanal and D-limonene were closely related to blanching, while the increases in the contents of dimethyl thioether, 2-acetyl-1-pyrroline, 2-methylpropanal, 3-methylbutanal, 2-methylbutanal 2-methyl-(E)-2-butenal compounds were highly correlated with spray drying. Thirty-three odor-active compounds were detected by GC-O, 10 of which had odor intensity value (OIV) equal to or larger than 3. Flavor profile analysis showed that the intensity of fruity aroma was the highest in fresh sweet corn, followed by floral, nutty and green aroma. After blanching treatment, the overall aroma intensity was decreased and in particular, the grassy aroma intensity was decreased significantly. After spray drying, the overall aroma intensity was significantly increased, the intensity of nutty and green aroma was significantly enhanced, and a strong barbecue aroma appeared.