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The present experiment entitled "Utilization of dragon fruit (Hylocereus spp.) peel
as a natural colourant in valorisation" was conducted at Department of Postharvest
Management, College of Agriculture, Vellayani during the period of 2021-2023, with the
objective to extract the dragon fruit peel colour and to utilize it as a source of natural
colourant in valorisation.
The study was carried out as three different continuous experiments utilizing good
quality ripe dragon fruit types of white flesh with pink skin (Hylocereus undatus) and
purple flesh with red skin ( Hylocereus polyrhizus) of uniform maturity.
In the first part of the study, colour extracts were prepared from peels of both white
and purple dragon fruits by different maceration techniques viz., hydromaceration,
maceration in ethyl alcohol, hydromaceration of freeze-dried peel, low temperature
hydromaceration and low temperature ethyl alcohol maceration for 24 hours adopting 1:2
peel to solvent ratio. Hydromaceration of purple dragon fruit peel produced extracts with
the highest betalain content (67.14 mg L-1
) and had an antioxidant activity of 62.49%.
Highest total antioxidant activity of 83.61% was found in extracts prepared by low
temperature hydromaceration of purple dragon fruit peel with a betalain content of 53.8 mg
L
-1
. Cost of production of 100 mL extract was least (Rs. 51.25) for hydromaceration of the
peels of white dragon fruit.
Extracts prepared by hydromaceration and low temperature hydromaceration were
subjected to ambient and low temperature (4 to 7 ⁰C) storage for three months for analyzing
storage stability in the second part of the experiment. In general, storage of colour extract
for three months resulted in reduction in betalain content and antioxidant activity. The
reduction was comparatively less in hydromacerated samples stored under low temperature
(4 to 7 ⁰C) condition. Hydromaceration of the purple dragon fruit peel was selected as the
extraction procedure for betalain content for utilization in squash preparation.
The peel colour extract prepared by hydromaceration of purple dragon fruit peel
was incorporated into white and purple fleshed dragon fruit squash prepared with and
without seed for analysis of chemical and sensory quality parameters in the last part of the
experiment. Squash prepared from purple fruit had higher betalain content where as
antioxidant activity was higher in white fruited squash. The squash prepared with seed had
higher antioxidant activity and ascorbic acid, but had lower betalain content. Peel colour
extract incorporated squash had higher betalain content and antioxidant activity compared
to squash without addition of peel colour.
Incorporation of seed and or peel had resulted in enhanced antioxidant activity in
both the fruit types. Seedless purple fleshed dragon fruit squash incorporated with peel
colour extract had highest betalain content (58.86 mg L-1
) with maximum overall
acceptability score (8.3); hence subjected to a storage period of three months. Betalain
content and antioxidant activity of squash were considerably reduced by three months.
Appearance, colour and flavor of the squash did not change during storage period whereas
the overall acceptability score was improved.
Hydromaceration of purple- fleshed dragon fruit peels for 24 hours using 1:2 peel
solvent ratio and storage at low temperature of 4 to 7 ⁰C can be recommended as the best
maceration method for betalain pigment extraction. Incorporation of this pigment into
white or purple fleshed dragon fruit squash significantly increased the betalain content,
proving the potential of purple dragon fruit peel as a natural food colour source.