USP scientists extract compounds from pomegranate peel to increase the shelf life of strawberries

Research by the São Carlos Chemistry Institute (IQSC) at the University of São Paulo (USP) demonstrated that pomegranate peel can be exploited sustainably, quickly and cheaply for different purposes. Using a new technique, scientists are able to extract 84,2% more antioxidants from the peel, substances that have preservative properties and are capable of delaying the aging process, making use of the portion of the pomegranate that goes to waste.

In the work, the researchers show that natural substances found in plants and known as NADES, an acronym in English for deep natural eutectic solvents, can be applied to remove the antioxidants found in pomegranate peels. Therefore, there is no need to use toxic options such as methanol or ethanol which, despite being a green solvent, evaporates easily and is explosive.

With the success of the new method, experts are now putting into practice a different stage of the study: incorporating pomegranate antioxidants obtained in an environmentally friendly way into coatings based on gelatin and chitosan, two biopolymers, to develop a protective film capable of increasing the shelf life of strawberries, the third item on the list of biggest losses in value in the fruit and vegetable sector of Brazilian supermarkets.

The study was awarded at the 2nd USP Postgraduate Meeting for its concern with the 12th Sustainable Development Goal of the United Nations (UN), Sustainable Consumption and Production, and is funded by FAPESP.

The scientists work in partnership with the Embrapa Instrumentação unit, from the Brazilian Agricultural Research Corporation, also located in São Carlos, to evaluate the effects of using polymeric coatings on the appearance and flavor of strawberries.

The first results, considering 14 days of storage in the refrigerator, indicate that the film can maintain its texture, delay contamination and prevent dehydration of the fruits.

“We want to contribute to reducing the disposal of strawberries by using pomegranate peel, which is responsible for high antioxidant activity, but is not used by the industry, being considered agro-industrial waste”, said Mirella Bertolo, doctoral student at IQSC-USP and main author of the work, in an interview with the IQSC Communications Office.

The research results were described in an article published in the scientific journal Journal of Cleaner Production.

Encouraging the use of natural products

The first challenge of the study was to obtain the antioxidants present in pomegranates from green solvents. “NADES were described after researchers began to wonder about the transport of nutrients in trees in frozen environments. They discovered that plants produce natural substances, with unique solubility properties, that enable this transport”, reported Stanislau Bogusz Junior, professor at IQSC and Bertolo's advisor, also in an interview with the IQSC Communications Office.

In the study, five NADES with different properties were tested. The researchers used statistical tools to analyze the interaction between variables, reducing the number of experiments needed, and arrived at an optimized process with choline chloride and lactic acid that resulted in an extraction of just 25 minutes with a high yield of compounds.

The professor explained that substances widely synthesized in plants have antioxidant properties, contributing to the neutralization of molecules that are produced in greater quantities through stress, disordered eating, exposure to pollution and consumption of alcohol and cigarettes.

Higher levels of free radicals, in turn, are linked to aging, hence the interest of the cosmetics industry in applying antioxidants in anti-wrinkle creams, for example. Its properties also arouse the interest of the food industry, as they have a preservative function.

Currently, the professor mentioned, many synthetic antioxidants are used to increase the shelf life of products and there is a growing interest among consumers in replacing them with healthier options.

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