Metabolic profile, health promoting properties and safety of Dawadawa (a fermented condiment) from Bambara groundnut (Vigna subterranea)

Abstract: Fermentation time and temperature are vital parameters influencing the composition of fermented foods and hence their quality. As such, response surface methodology (RSM) was used to optimize fermentation conditions of Bambara groundnut (BGN) to obtain dehulled and undehulled dawadawa. The effect of the various fermentation time and temperature combinations were investigated on mycotoxin reduction. Fermentation caused significant (p 0.05) reduction in the concentrations of mycotoxins. For example, 100% reduction in aflatoxin B1 (AFB1), aflatoxin G1 (AFG1), fumonisin B1 (FB1), fumonisin B2 (FB2), ochratoxin A (OTA), T2-toxin (T2), alphazearalenol (α-ZOL) and beta-zearalenol (β-ZOL) were observed in dehulled samples. This reduction was much higher in dehulled (DD) as compared to undehulled (UDD) dawadawa. Based on the fact that pH and titratable acidity (TTA) are vital parameters in the fermentation process and final properties of fermented food products, two optimal dawadawa samples were selected based on this and subsequently investigated. These were samples obtained at 35 oC for 84 h and 35 oC for 120 h, for dehulled and undehulled dawadawa, respectively. Accordingly, these samples were adopted to streamline the study and select the optimal fermentation conditions for other phases of the research and parameters to be investigated. Dawadawa products obtained under these conditions were subsequently investigated for total phenolic content (TPC), total flavonoid content (TFC), antioxidant activities (AA) and the presence of phenolic compounds using ultrahigh performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS) system. A gas chromatography high resolution time-of-flight mass spectrometry (GC-HRTOF-MS) system was also used to profile other metabolites. Processing of dawadawa from BGN caused a decrease in most of the phenolic compounds including quinic acid, medioresinol, quercetin-3-O-galactoside-7-O-rhamnoside with a corresponding increase in TPC, TFC and AA as noted. The levels of phenolic compounds and antioxidant activities were higher in undehulled than dehulled dawadawa. Profiling of the metabolites in the BGN and dawadawa samples on GC-HRTOF-MS revealed modifications in the levels of the compounds recovered, with esters constituting the largest group of compounds, with prominent presence of ketones, phenols, sterols, fatty acid esters and alcohols. Investigations into the nutritional and antinutritional components of BGN and derived dawadawa samples showed a reduction in oxalate, tannin and phytic acid contents. Increases in proteins and ...D.Tech. (Food Technology