Abstract:
Peppermint oil (PO) has valuable medicinal properties such as high antioxidant activity and
is used to treat numerous diseases including irritable bowel syndrome and indigestion.
However, it is sensitive to light and heat. Furthermore, it could cause heartburns during its
passage through the stomach. Therefore, the objectives of this research were to make
microcapsules of PO, which can help to overcome the fore stated complications. PO
microcapsules that are stable under acidic pH of the stomach can be taken as a dietary
supplement. PO microcapsules were synthesized by complex coacervation method using
gelatin and gum acacia wall materials. Formaldehyde was used to make cross links
between gum acacia and gelatin to increase the stability of the wall. Gelatin enteric coating
was used to further increase the strength of the microcapsule wall. Morphology of the
synthesized microcapsules was studied using the optical microscope and was found to be
spherical. Encapsulation of PO was confirmed by the UV-Visible spectra of mechanically
crushed microcapsules. Antioxidant capacities (AOC) of the encapsulated PO were
assessed using the Folin-Ciocalteu reagent and were found to be 33.3 (±7) mg pyrogallol
equivalents (PGE)/g and 38.7 (±1) mg PGE/g for gelatin coated and non-coated
microcapsules respectively. In order to assess the stability of the microcapsules, they were
subjected to acidic conditions similar to the stomach and the resulting microcapsules and
the acidic solutions were analyzed for their AOC. It was found that only 4-9% of active PO
was lost from the microcapsule during the acidic treatment, hence indicating the capacity
of PO microcapsules to significantly retain the encapsulated PO. After subjecting to acidic
conditions similar to the stomach, the gelatin coated and non coated microcapsules
retained 91% and 96% of active PO respectively. Pure PO directly added to the acidic
solution displayed a loss of 44% of AOC, hence signifying the extra stability of
microencapsulated PO. The acid treated PO microcapsules were then subjected to
conditions similar to the intestine by treating with neutral solution in the presence and
absence of a protease enzyme (Bromelain). In the absence of the enzyme, both gelatincoated
and non-coated microcapsules indicated 3-5% release of active PO to the solution.
In the presence of the protease, both types of microcapsules indicated 8-18% release of
active PO. This ensures the enhanced release of encapsulated PO inside the intestine in
the presence of digestive proteases that can digest the microcapsule wall, similar to
bromelain.
