FERMENTING KALE VEGETABLE (Brassica oleracea Var Sabella) IMPROVES ITS PROPERTIES AS A FUNCTIONAL FOOD

Abstract

The properties of kale as a functional food are well known. Fermentation is a process that has been shown to improve the health impacts of foods. In this study, we sought to determine how fermentation further improves or augments the functional food properties of kale. We tested six different fermentation methods which included traditional practices and inoculation with different bacterial species and compared outcomes to the unfermented control. After 16 days of fermentation, we quantified (i) selected bioactive components and (ii) anti-nutritional factors. We then determined (i) the antioxidant capacity of the whole vegetable, (ii) the microbiota composition of the vegetable, and (iii) the anti-inflammation capacity of the ethanolic extract of the vegetable. Fermentation significantly increased (i) the quantities of total polyphenols from 8.54 to 10.71 mg GAE/g (ii) sulforaphane from 960.8 ± 41.76 to 1777 ± 45.95 μg/g, and (iii) antioxidant capacity from 61.99 to 67.37 % respectively, and antinutritional factors oxalate and tannin content significantly reduced by 49 % and 29.83 % respectively. Fermented kale extract exhibited potent anti-inflammatory effects in macrophages by reducing the iNOS expression by 84.3% and TNF-α, IL-1β, and IL-6 mRNA levels by 62, 68, and 85.5 %, respectively. Fermenting kale changed the surface microbiota by reducing the population of the inflammation-inducing Proteobacteria while increasing health-promoting Firmicutes; including Lactobacillus. All fermentation methods had a beneficial impact compared to the unfermented control, but the mixed culture of L. lactis and L. acidophilus was the most effective. In summary, fermenting enhanced the health benefits of kale by increasing the concentration of total polyphenol, sulforaphane content, antioxidant capacity, anti-inflammation capacity, and reducing the quantity of anti-nutritional factors. Furthermore, it promoted the prebiotic and/or probiotic vehicle properties of the vegetable by changing the proportion of beneficial bacteria and those associated with inflammation.