Effect of Growth Stages and Lactic Acid Fermentation on Anti-Nutrients and Nutritional Attributes of Spinach (Spinacia oleracea)

Abstract

Spinach (Spinacia oleracea) is a winter-season green, leafy vegetable grown all over the world, belonging to the family Amaranthus, sub-family Chenopodiaceae. Spinach is a low-caloric food and an enormous source of micronutrients, e.g., calcium, folates, zinc, retinol, iron, ascorbic acid and magnesium. Contrarily, it also contains a variety of anti-nutritional factors, e.g., alkaloids, phytates, saponins, oxalates, tannins and many other natural toxicants which may hinder nutrient-absorption. This study was aimed at investigating the effect of fermentation on improving the nutrient-delivering potential of spinach and mitigating its burden of antinutrients and toxicants at three growth stages: the 1st growth stage as baby leaves, the 2nd growth stage at the coarse stage, and the 3rd growth stage at maturation. The results revealed the significant (p < 0.05) effect of fermentation on increasing the protein and fiber content of spinach powder from 2.53 to 3.53% and 19.33 to 22.03%, respectively, and on reducing total carbohydrate content from 52.92 to 40.52%; the effect was consistent in all three growth stages. A significant decline in alkaloids (6.45 to 2.20 mg/100 g), oxalates (0.07 mg/100 g to 0.02 mg/100 g), phytates (1.97 to 0.43 mg/100 g) and glucosinolates (201 to 10.50 µmol/g) was observed as a result of fermentation using Lactiplantibacillus plantarum. Fermentation had no impact on total phenolic content and the antioxidant potential of spinach, as evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric-reducing antioxidant power (FRAP) assays. This study proposes fermentation as a safer bioprocess for improving the nutrient-delivering potential of spinach, and suggests processed powders made from spinach as a cost-effective complement to existing plant proteins.

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

“…Fermentation treatment increased the ash, protein and fiber contents, whereas moisture, fat and carbohydrate contents decreased among B. campestris samples, and the trend was similar for all three stages. In addition, the results of the present investigation agree with previous findings of [ 54 , 55 , 56 ]. A continued fermentation for a long time may result in decreased fat content that could be attributed to lipolytic activities and the utilization of lipids as an energy source by the fermenting microorganisms [ 57 ].…”

“…Results of the present investigation ( Table 5 ) showed that blanching causes a decrease in total phenolic and flavonoids, whereas fermentation causes the opposite. Our results agree with results obtained by other researchers who found that fermentation leads to a slight increase in phytochemical contents [ 55 , 61 ]. Our findings indicated that the ethanol, n -hexane and methanol extracts have higher flavonoid concentrations in B. campestris as compared to the total flavonoid content (TFC) in the various vegetable samples ranging from 1.09 to 3.59 mg CE/g.…”

“…The stable free radical scavenging potential and FRAP values of samples extracted with n -hexane, acetone and ethanol were in the order of raw, followed by fermented, and then blanched, but an inverse order was observed in the case of the methanol extract. Previously, the DPPH inhibition potential of fermented samples extracted with n -hexane and ethanol was slightly lower as compared to non-fermented samples, but a slight increase was observed in the case of water extraction [ 55 ]. In another investigation, fermentation caused a notable increase in DPPH assay wherein IC 50 of fermented sample decreased from 6.3 to 2.9 mg/mL [ 61 ].…”