Effect of Short-Term Lactic Fermentation on Polyphenol Profile and Antioxidant Capacity in White and Red Quinoa...

Quinoa (Chenopodium quinoa Willd.) is a pseudocereal originally grown in the Andean region of South America. This study focused on investigating the changes in phenolic profile and antioxidant capacity in white and red quinoa varieties after short-term fermentation with Lactiplantibacillus plantarum 299v^®. During fermentation, pH and lactic acid formation were monitored every three hours until pH was below 4.6. The quinoa phenolic profile was quantified via LC-UV-MS. Total polyphenol content (TPC) and total antioxidant capacity (DPPH and FRAP) were determined via spectrophotometric methods. The findings showed that fermentation resulted in a significant increase (p < 0.001) in TPC from 4.68 to 7.78 mgGAE·100 g^-1 for the white quinoa and from 5.04 to 8.06 mgGAE·100 g^-1 for the red quinoa variety. Gallic acid was the most abundant phenolic acid detected in unfermented quinoa samples (averaging 229.5 μg·g^-1). Fermented white quinoa showed an 18-fold increase in epicatechin, while catechin was found only in fermented red quinoa (59.19 μg·g^-1). Fermentation showed a significantly positive impact on the iron-reducing antioxidant capacity (FRAP) of quinoa (p < 0.05). Red quinoa had a higher FRAP antioxidant capacity than the white variety; a similar trend was observed with the DPPH assay. There was a significant correlation (r > 0.9, p < 0.05) between TPC and antioxidant capacity. In conclusion, short-time lactic fermentation effectively increased phenolic content and antioxidant capacity in both quinoa varieties. Overall, red quinoa showed higher polyphenol content and antioxidant capacity compared to the white variety.