Impact of cooking and fermentation by lactic acid bacteria on phenolic profile of quinoa and buckwheat seeds

In this work, quinoa and buckwheat cooked seeds were fermented by two autochthonous strains of lactic acid\r\nbacteria isolated from the corresponding seeds, namely Lactobacillus paracasei A1 2.6 and Pediococcus pentosaceus\r\nGS·B, with lactic acid chemically acidified seeds as control. The impact of cooking and fermentation on the\r\ncomprehensive phenolic profile of quinoa and buckwheat seeds was evaluated through untargeted ultra-highpressure\r\nliquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UHPLC-QTOF-MS).\r\nSamples were analyzed also for in vitro antioxidant capacity (as FRAP and ORAC assays) and total phenolic\r\ncontent (TPC). The in vitro spectrophotometric assays highlighted that the microbial fermentation was more\r\nefficient in increasing (p < .05) the TPC and in vitro antioxidant potential in quinoa cooked seeds. However, an\r\nincrease (p < .05) in TPC and ORAC radical scavenging was observed in both pseudocereals after the different\r\ncooking processes (i.e., boiling or toasting).\r\nThe untargeted phenolic profiling depicted the comprehensive phenolic composition in these matrices. Raw\r\nseeds of both pseudocereals possessed a similar phenolic content (4.4 g kg−1 equivalents; considering free and\r\nbound fractions). Besides, the metabolomics-based approach showed that all treatments (i.e., cooking and fermentation)\r\ninduced the release of specific classes, namely phenolic acids and tyrosols. The PLS-DA multivariate\r\napproach identified in flavonoids the best markers allowing to discriminate the different treatments considered\r\n(i.e., cooking, chemical acidification and microbial fermentation). These findings support the use of cooking and\r\nmicrobial fermentation to ensure the health-promoting properties of non-wheat grains, such as buckwheat and\r\nquinoa.