According to new research, a chitosan-based coating can be used on avocados to help preserve them for longer periods.

Statista has reported that the global avocado market was valued at over nine billion US dollars in 2021. In fact, it has been forecasted to reach more than 19.9 billion US dollars by 2026.

However, researchers at the American Chemical Society (ACS) have defined then as being “notoriously finicky, going from pale green and firm to brown and mushy in the blink of an eye”.

As well as producing a chitosan-based coating, the researchers have developed an imaging technique that they claim can be used to “quickly predict their shelf life”.

The researchers explained that they have developed techniques to delay ripening, using compounds such as 1-methyl-cyclopropene (1-MCP). More recently, studies have shown that naturally-derived chitosan (a biomaterial derived from shellfish exoskeletons) imparts antimicrobial activity when applied as a coating to fruits, including avocados.

The study team, comprised of Angie Homez-Jara, Angelica Sandoval-Aldana and colleagues, set out to compare two preservation methods used to keep avocados fresh. To do so they treated commercially mature Hass avocados with either gaseous 1-MCP or water-based solutions that contained different concentrations of chitosan.

Mimicking realistic transportation conditions, treated and untreated avocados were chilled at 41 degrees Fahrenheit for 21 days and then moved to room temperature to simulate a grocery store environment until they were rotten. Untreated samples and those treated with either 1-MCP or one percent chitosan-based coating were at optimal ripeness for six days.

Results revealed that avocados treated with a 1.5 percentchitosan-based coating were best for 12 days. However, these samples reportedly had uneven firmness once they were ripe, as well as green and purplish spots in the peel, something researchers say shows that the chitosan coating “could be improved in the future.”

Throughout the study, the researchers also imaged the entire surface of the fruits with hyperspectral cameras in the visible and near-infrared spectrum. Then the reflectance data from the images were compared to the avocados’ firmness, peel colour, oxygen consumption and weight loss, using various computer models.

Two machine learning models best explained the changes that occurred during the avocados’ ripening and could predict their remaining shelf life.

Overall, the researchers found that their chitosan-based coating and prediction technique “could help improve the shelf life and quality of avocados for sale”.