The preservation of freshly cut fruit is one particularly promising application, but research suggests that there could be many other possible uses for passion fruit peel.
Discovering more uses for passion fruit peel
Health-conscious consumers who value the high concentration of vitamins and nutrients and the antioxidant properties of passion fruit pulp and juice have led to a growing demand for the fruit, with consumption increasing between 15 and 20% in recent years.
More than half of all passion fruit production originates in Brazil, which is also the largest consumer market for the fruit. Production also takes place in tropical regions around the world beyond South America – from Kenya to Florida to Indonesia.
Since the fruit is primarily grown to produce juice and other edible products, such as jams that use passion fruit pulp and seeds, only about a quarter of each typical fruit is prepared for consumption, with the bulk of the organic material ending up as waste. The peel alone makes up around half of the passion fruit’s weight, with most peels ending up either as animal feed or simply discarded, potentially causing environmental damage.
The high proportion of wasted organic material lost during the production process and the unique properties of its components have driven interest in the potential uses of passion fruit byproducts, resulting in a growing body of academic research on passion fruit peel valorisation.
A 2020 study from researchers at several Malaysian universities showed that the antibacterial and antioxidant properties of passion fruit peel could make it an effective preservative for meat products.
Other studies have investigated the use of passion fruit waste as a means of removing pollutants from water, as a biofuel, as a form of activated carbon, or as a component in food systems.
Beneficial bioactive compounds found in passion fruit peel
Research has also identified various remarkable characteristics of passion fruit peel that offer possibilities as an ingredient in nutraceuticals, pharmaceuticals, and functional foods.
Researchers from the University of Johannesburg, who published their findings in the journal Antioxidants in 2022, highlighted that the peel contains even more functional properties than the pulp itself – including “impressive antimicrobial, antioxidant, and antitumour properties” that are linked to the presence of “anthocyanins, ascorbic acid, flavonoids, carotenoids, and phenolics”.
The study also found two stilbene compounds – piceatannol I and piceatannol II – that have previously been found in a limited number of sources, including red wine, grapes, and peanuts. The study cites research that suggests stilbenes could protect against chronic illnesses such as cancer, neurodegenerative conditions, and cardiovascular diseases.
However, unlike compounds in passion fruit pulp and juice, the beneficial compounds found in the peel are more sensitive and require further processing. Passion fruit peel powder could offer an effective way to protect bioactive compounds and serve as an additive in functional foods and beverages.
Edible and durable food coating
The University of Johannesburg study primarily examined the potential for powdered passion fruit peel to function as a coating and functional ingredient.
The researchers encapsulated passion fruit peel extract in three different carriers (gum arabic, maltodextrin, and waxy starch) and produced powders that they tested under different conditions.
Each of the resulting freeze-dried powders was edible, rich in polyphenols and antioxidants, and shelf-stable, making them very well suited as a coating material to preserve foods that spoil or dehydrate easily – such as freshly cut fruits and vegetables – without altering their colour, flavour, or smell.
Each of the different carriers affected the properties of the powder. For instance, the gum arabic and maltodextrin powders retained more of the antioxidant properties, while the waxy starch maintained more of the phenolic compounds.
The study suggests combining carriers for optimal results and recommends further research into the preservative usage of the powders.
The successful encapsulation of passion fruit peel also opens the door for further experimentation with byproducts from other fruits or vegetables that are currently considered mere waste, building on a growing trend of increasing options for biodegradable and edible coating materials
