Lactic Acid Fermentation Ameliorates Intrinsic Toxicants in Brassica campestris L. Leaves Harvested at Different Growth Stages

Brassica campestris (syn. Brassica rapa) is often known as mustard and is grown worldwide owing to its health-promoting characteristics associated with the presence of nutrients and phytochemicals. Along with the nutritional components, B. campestris also contains anti-nutrients (phytates, oxalates, tannins, alkaloids, saponins) that can cause adverse severe health effects to consumers, including rashes, nausea, headaches, bloating and nutritional deficiencies. In the present study, heating (blanching) and fermentation (Lactiplantibacillus plantarum) treatments were applied to reduce the load of the anti-nutrients of B. campestris leaves harvested at three different growth stages: the first stage (fourth week), the second stage (sixth week) and the third stage (eighth week). Results revealed that fermentation treatment using Lp. plantarum increases the ash (5.4 to 6%), protein (9 to 10.4%) and fiber (9.6 to 10.7%) contents, whereas moisture (0.91 to 0.82%), fat (9.9 to 9.1%) and carbohydrate (64.5 to 64.2%) contents decreased among B. campestris samples, and the trend was similar for all three stages. Blanching and fermentation lead to the reduction in phytates (46, 42%), saponins (34, 49%), tannins (1, 10%), oxalates (15, 7%) and alkaloids (10, 6%), separately as compared to raw samples of B. campestris leaves. In contrast, fermentation had no considerable effect on phytochemical contents (total phenolic and total flavonoids) and antioxidant potential (DPPH and FRAP). The action of blanching followed by fermentation caused more decline in the aforementioned toxicants load as compared to blanching or fermentation alone. Structural modifications in blanching and the biochemical conversions in fermentation lead to enhanced stability of nutrients and antioxidant potential. Taken together, these findings suggest blanching followed by fermentation treatments as a reliable, cost-effective and safer approach to curtail the anti-nutrient load without affecting the proximate composition, phytochemical attributes and antioxidant activity.