Quality and Antioxidant Characteristics of Roasted Maize Tea with Different Moisture Contents
We investigated the quality characteristics and the antioxidant efficacy of roasted maize tea according to different moisture contents (9% to 14%) using the puffing system (PS) and the roasting system (RS). Compared with the RS, the PS caused higher turbidity (0.017 vs. 0.003 in PS-14% vs. RS-14%), brown color intensity (0.170 vs. 0.059 in PS-14% vs. RS-14%), a-values (0.20 vs. -0.44 in PS-14% vs. RS-14%), b-values (7.90 vs. 5.57 in PS-14% vs. RS-14%), and a lower L-value (19.67 vs. 21.03 in PS-14% vs. RS-14%). Total polyphenol and flavonoid contents of roasted maize tea were increased along with the moisture content and they were higher with the PS (polyphenol; 5.95 mg GAE/g, flavonoids; 1.27 CE/g in PS-14%) than with the RS (polyphenol; 5.39 mg GAE/g, flavonoids; 1.12 mg CE/g in RS-14%). The DPPH and ABTS radical scavenging effects of roasted maize tea were also increased along with the moisture content, and the scavenging efficacy was significantly higher with the PS (DPPH; 160 mg TE/100g, ABTS; 507 mg TE/100g in PS-14%) compared with the RS (DPPH; 120 mg TE/100g, ABTS; 362 mg TE/100g in RS-14%). The polyphenol levels were significantly correlated with turbidity, brown color intensity, and L, a, and b-values of the roasted maize tea. In addition, an increase of the total polyphenol content in roasted maize tea induced antioxidant activities. As a result, an increase in polyphenols during the roasting process induced antioxidant activities which could prevent damage from free radicals.