Antioxidant and antimicrobial capacity of aqueous extract of kale and potential supplementation in fermented dairy beverage

The objective of this work was to evaluate the antioxidant and antimicrobial capacity of Kale leaves, as well as to quantify the levels of phenolic compounds and flavonoids present in its aqueous extract, and the viability when added to a fermented milk drink. The leaves were subjected to four treatments: fresh crushed in a blender, fresh sprayed with liquid nitrogen, dried in an oven at 45°C for 72 hours and frozen. Antioxidant activity, concentration of total phenolic compounds, flavonoids and antimicrobial activity were determined. To prepare the dairy drink, the amounts of 5%, 10% and 15% of the dry extract of Kale leaves were added, as well as 15% of the dry extract with sorbate and the control treatment. Furthermore, it determined the antioxidant activity and the number of lactic acid bacteria in the drink. The dried and frozen leaves showed better antioxidant activity and, when compared to fresh powdered leaves, they did not differ in phenolic compounds, presenting the best contents. Fresh powdered leaves showed the highest flavonoid yield. The aqueous extracts of kale leaves did not show antibacterial activity against the studied microorganisms. The abstract did not show antioxidant capacity contents of total phenolic compounds and flavonoids in kale subjected to different treatments.