Changes of Antioxidant and Functional Components in Various Salt-Aged and Fresh Radishes after Fermentation

Many studies have found that salted radishes offer various health benefits, such as enhancing antioxidant levels and increasing GABA. This study fermented a mixture of 20-year-old salted radishes (20-S. radishes), 2-year-old salted radishes (2-S. radishes), 20-year-old salted radishes combined with fresh radishes (R + 20-radishes), and fresh radishes with eight whole grains fermentation as a starter (EGS) for 8 weeks. EGS was derived from the saccharified fermentation of millet, wheat, sorghum, black rice, buckwheat, pearled rice, black glutinous rice, and quinoa, serving as a carbon source for microorganisms and replacing the traditional sugar-based fermentation method. During the fermentation process, the bacterial count of the 20-year-old salted radishes significantly increased to 11.08 ± 0.03 log CFU/mL, which was much higher than the other three groups. Pichia manshurica LYC1722 was identified in all four groups after isolation. After 8 weeks of fermentation, 20-S. radishes showed the highest concentrations of gamma-aminobutyric acid (GABA) and glucuronic acid in functional components, at 18.40 ± 0.69 ppm and 14,162.84 ± 48.22 ppm, respectively. In terms of antioxidant components, 20-S. radishes exhibited a total phenolic content (TPC) and total flavonoid content (TFC) of 0.81 ± 0.01 mg/mL and 42.78 ± 0.60 mg/L, respectively. Regarding antioxidant capability, 20-S. radishes displayed ABTS radical scavenging activity and DPPH radical scavenging activity at 184.42 ± 0.28 μg/mL and 9.13 ± 0.28 μg/mL, respectively. These values were the highest among the four groups evaluated. Fresh radishes exhibited the highest angiotensin-converting enzyme (ACE) inhibition after fermentation among the four groups, reaching 69.04 ± 2.82%, slightly higher than 20-S. radishes. These results show that 20-S. radishes are expected to become a novel health beverage in the future.