According to University of Johannesburg study, the high quantities of antioxidants and polyphenols in passion fruit peels offer a significant potential for preserving fresh fruits and cuts in an edible food covering. A covering like this can help to reduce plastic packaging and spoilage in supply chains.
The peels of passion fruit (Passiflora edulis Sims) were isolated, microencapsulated, freeze-dried, and powdered by the researchers from an organic farm. This kind is well-known for its therapeutic properties. Passion fruit is mostly farmed for concentrated juice across the world. Their metabolomic and other analyses published in Antioxidants show that the powders possess the properties required for a high-quality, stable, and edible food coating. The powders could also be useful in natural food additives.
When fresh produce is packaged in plastic, the plastic creates a ‘micro-atmosphere’, says Prof Olaniyi Fawole, from the University of Johannesburg. And that puts the brakes on what oxygen can do to the produce.
“Oxygen is the bad guy, it causes a lot of biochemical degradation. So we want to limit the oxygen that gets to the produce. And we also want to limit dehydration. Edible food coatings can potentially solve both the oxygen and dehydration problems in the cold chain,” he adds.
The ideal coating: “If you coat the product, you reduce the interference from a high oxygen atmosphere, because there is a barrier. Dehydration is prevented because the coating keeps the moisture on the inside,” says Fawole.
Any such coating, however, must have a high antioxidant content to assist prevent decomposition due to oxidation, as well as antimicrobials. An edible coating should not interfere with the product’s colour, look, or flavour.
Fresh fruit slices, which degrade quicker than entire fruit and are subjected to significantly more germs and dehydration, might benefit even more from such a covering.
Antioxidants and polyphenols are preserved by microencapsulation. The significant antioxidant and polyphenol content of the passion fruit peels was retained through the microencapsulation procedure. This is crucial since industrial processes, pH, high storage temperatures, oxygen, light, solvents, and metal ions quickly degrade antioxidants and other bioactive chemicals.
The microencapsulation was carried out using one of three carriers: gum arabic (GA), maltodextrin (MT), or waxy starch (WS). They discovered that the encapsulation effectiveness (EE) of the three carriers ranged from 82.64 to 87.18%. This suggests that antioxidants and polyphenols should be effectively retained within the coated powder particles’ microcapsules.
The antioxidants and polyphenol content of each encapsulated powder were then determined.
Results of bioactive analyses Plants include a plethora of phytochemicals, such as polyphenols, and no one assay can accurately reflect the antioxidant content of the powders. Instead, the researchers utilised two studies to determine how much the encapsulating procedure changed the antioxidant activity of the bioactive chemicals in the microparticles.
The first test, DPPH radical scavenging activity, revealed that all three carriers had 45.85 to 51.29 mM Trolox Equivalent (TE)/ g DM (WS).
The ferric reducing antioxidant power (FRAP) test revealed that the carriers had 32.30 – 37.47-mM TE/g DM.
Trolox is a water-soluble synthetic antioxidant that has been employed as a standard antioxidant in various antioxidant tests. Consumers may doubt the safety of synthetic antioxidants, thus there is a push for alternatives.
“The results mean that the encapsulated powders could be viable alternatives to synthetic antioxidants and can provide valuable properties such as antibrowning and anti-senescence behaviour. They also offer the additional benefit of being edible,” says Fawole.
The researchers used liquid chromatography mass spectrometry to conduct metabolomic tests to determine which polyphenols are present in the microencapsulated powders (LC-MS).
Vanillic acid glucoside, quercetin, citric acid, gluconic acid, and caffeic acid are commercially relevant polyphenols retained at usable quantities in microencapsulated powders.
Long shelf life, many doses, excellent solubility
“An edible coating or natural food preservative may be potent, but if its raw material is not stable, it is useless. For example, if it is hygroscopic, meaning it absorbs moisture, it is not suitable for industrial scale applications,” says Fawole.
“These microencapsulated powders are non-hygroscopic, for all three carriers. If these are well-packaged, and stored cool and dry, they should last up to six months. Also, you can open up a container, use what you need, close the container, and the rest will be stable. It won’t be necessary to use the contents of an entire container in one go.”
Overall, the extensive laboratory results show that microencapsulated powders derived from passion fruit peels are an excellent active component in edible food coatings and natural food additives, especially for ‘naked’ fresh fruit and fresh cuts.