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Title: The prebiotic effects of amadumbe (Colocasia Esculenta) and okra (Abelmoschus esculentus) mucilage
Authors: Gajadhar, Sharmista 
Keywords: Probiotics;Amadumbe;Okra
Issue Date: 2023
Prebiotics have been shown to aid in the improvement and maintenance of human health
through positive manipulation of gut microbiota. Diet-induced changes in gut microbial
diversity has been recognized as a factor which contributes to the rising epidemics of chronic
illnesses in both developed and developing countries.
Traditional crops, amadumbe (Colocasia esculenta) and okra (Abelmoschus esculentus (L.)
Moench) offer nutritional security to many communities in South Africa. These crops are rich
in mucilage and are presumed prebiotics. Structural composition and functional properties of
polysaccharides like mucilage are suggested to influence their fermentability by gut microbiota
and potential health effects. The purpose of this study was to investigate the prebiotic effects of
amadumbe and okra mucilages for potential application as dietary supplements.
Mucilage was extracted from amadumbe and okra by cold water extraction. Purified mucilage
was obtained by Sevag method, lipid removal and thereafter dialyzed. The composition and
structure of crude and purified mucilage were analyzed using Fourier transform infrared
spectroscopy (FT-IR), size exclusion chromatography (SEC) and high pressure liquid
chromatography (HPLC). Functional properties including water and oil holding capacity,
swelling and solubility were determined. The prebiotic potential of amadumbe and okra
mucilage was carried out by in- vitro fermentation using human faecal sample.
Glucose was the common monosaccharide present in both amadumbe and okra mucilage.
Monosaccharides present in amadumbe mucilage were arabinose, mannose and xylose, while
galactose, ribose and rhamnose were the main monosaccharides present in okra mucilage. The
presence of β-glucan was found to be higher 0.20 g/100 g in amadumbe mucilage than in okra
mucilage 0.07 g/100 g. The resistant starch content in amadumbe mucilage was higher 4 g/100
g than in okra mucilage 0.7 g/100 g. Asparagine, proline, glutamine, and threonine were the
most common amino acids found in both amadumbe and okra mucilage samples. Purified
amadumbe and okra mucilage displayed the same characteristic peaks as crude amadumbe and
okra mucilage in the FT-IR spectrum but at a lower intensity suggesting that purification
contributed to a more stable and uniform structure. The FT-IR spectrum indicated the presence
of uronic acid and hydroxyl groups which confirm the existence of carbohydrate in both
amadumbe and okra mucilage.
The molecular weight of crude amadumbe and okra mucilages ranged between 219 and 224
kDa while molecular weight of purified amadumbe and okra mucilage ranged between 220 and 244 kDa. The purification process was seen to improve functional properties such as the water
holding capacity, swelling and solubility of mucilages. In comparison to okra mucilage, crude
and purified amadumbe mucilage showed low water holding capacity 5 and 9 g/100 g and high
percentage solubility 61 and 73%. Amadumbe mucilage had a slightly higher oil holding
capacity 11 g/100 g in comparison to okra mucilage 10 g/100 g.
During in-vitro fermentation, inulin (positive control) rapidly decreased the pH of the
fermentation medium from 7.0 to 6.5, in comparison to amadumbe (7.0 to 6.7) and okra (7.0 to
6.8) mucilage. At the end of fermentation inulin had maximum gas production of 233.19 mL,
followed by amadumbe mucilage 158.98 mL and okra mucilage 113.98 mL. These results
suggest inulin is more easily fermented by microbes compared to amadumbe and okra mucilage.
Gut microbiota analysis at phylum level showed that amadumbe mucilage stimulated the
proliferation of Actinobacteria and reduced the presence of Firmicutes in comparison to okra
mucilage. At species level, okra mucilage promoted the growth of Bacteroidaceae
bacteroidetes, Bacteroides ovatus and Bacteroides uniformis. These species are known to assist
in protection of the gut and are capable of providing nutrients to other microbial species. This
suggest that amadumbe and okra mucilages are fermented differently by gut microbiota
possibly due to differences in their structure and composition.
This study concluded that amadumbe and okra mucilages has potential to be utilized as an
emerging prebiotic in food applications or as supplements.
Submitted in complete fulfilment for the Degree of Master of Applied Sciences in Food Science and Technology, Durban University of Technology, Durban, South Africa, 2023.
Appears in Collections:Theses and dissertations (Applied Sciences)

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