Abstract:
Traditional preparation of African indigenous vegetables (AIVs) such as African black
nightshade (Solanum nigrum) and African spiderplant (Cleome gynandra) involves either boiling
and discarding the first water or lengthy boiling. Fermentation is considered a better alternative
processing technique due to the enhanced retention of phytochemical contents and sensory properties.
However, little is known about the impact of lactic acid fermentation on the phytochemical content,
antioxidant capacity, sensory acceptability and microbial safety of the African black nightshade and
African spiderplant. This study aimed to ferment AIVs using combined starter cultures (Lactobacillus
fermentum and Lactococcus lactis) and further determine their effect on the phytochemical content
(phenolic compounds and flavonoids), antioxidant capacity, sensory acceptability and microbial safety
of the vegetables. There was a marked increase in phenol and flavonoid contents in all fermented
vegetables (p < 0.05). The highest phenol content was 228.8 mg/g GAE (gallic acid equivalent) in
the starter-culture-inoculated African black nightshade, while flavonoid content was 10.6 mg/g QE
(quercetin equivalent) in the same. Starter-culture-inoculated AIVs presented significantly higher
antioxidant capacity with a 60–80% radical scavenging activity compared to levels in uninoculated
batches (p < 0.05). Fermented vegetables were more liked than the boiled vegetables and were
microbiologically safe. In conclusion, lactic fermentation of AIVs increased phytochemical contents
(phenolic compounds and flavonoids), maintained antioxidant capacity and improved product safety
and sensory acceptability. Therefore, fermentation and consumption of the African indigenous
vegetables are to be encouraged.
