If you've ever eaten a pomegranate, you'll know that a great deal of the fruit is composed of its thick skin – which simply gets thrown away. Soon, however, that skin could be used in an edible coating which will help keep strawberries from spoiling.
Although all fruits are prone to spoilage, strawberries have a particularly short shelf life.
This is partially due to the fact that they're very moist and quite acidic, both of which make them ideal habitats for fungi. Additionally, strawberries have an unusually high rate of respiration, which causes them to quickly break down and decay.
As a result, a number of groups have set about developing edible coatings that allow the berries to stay fresh longer. Among other ingredients, these substances have been composed of cannabidiol, corn, eggs, silk, and pectin.
Now, there's also one made from antioxidant-rich pomegranate peels.
Led by Prof. Stanislau Bogusz Junior, scientists at Brazil's University of São Paulo started by utilizing natural deep eutectic solvents to extract a variety of phenolic compounds from waste pomegranate skins.
Those compounds, which have antioxidant and antimicrobial properties, were then mixed with two polymers: a gelatin, and a biopolymer known as chitosan. The latter is obtained from seafood-industry shellfish waste – in this case, the internal shells of squid – and in fact has an antimicrobial effect of its own. When applied to strawberries via a simple dipping process, the coating formed a thin film that blocked microbes, moisture loss, and gas exchange (which slowed the respiration process).
In lab tests, it was found that coated strawberries didn't show any signs of fungal contamination until six to eight days after being placed in refrigerated storage. By contrast, an uncoated control group became contaminated after just four days. The coated strawberries additionally maintained their firmness, color, texture and aroma, plus very importantly, they were found to taste no different than their uncoated counterparts.
Bogusz and colleagues are now exploring the possibility of licensing the technology to commercial partners. A paper on the research was recently published in the journal Food Chemistry.
This is far from the first proposed use for pomegranate-peel extracts. Previous studies have suggested that they could also be used to remove pharmaceuticals from wastewater, slow cellular aging, and protect unborn babies' brains.
Source: Agência FAPESP
