International. ACS Food Science & Technology researchers report a chitosan-based coating that preserves avocados for longer periods, going from a pale, firm green color to brown and soft in the blink of an eye.
The team also developed an imaging technique to quickly predict its lifespan.
Researchers have developed techniques to delay maturation using compounds such as 1-methyl-cyclopropene (1-MCP). And more recently, studies have shown that naturally occurring chitosan, a biomaterial derived from the exoskeletons of shellfish, imparts antimicrobial activity when applied as a coating to fruits, including avocados.
The researchers wanted to compare the effectiveness of the two preservation methods on the quality and shelf life of avocados. These treated commercially ripe Hass avocados with gaseous 1-MCP or water-based solutions containing different concentrations of chitosan.
Mimicking realistic transportation conditions, treated and untreated avocados were cooled to 41 degrees Fahrenheit for 21 days and then moved to room temperature to simulate a grocery store environment, until they rotted.
Untreated samples and those treated with 1-MCP or a 1% chitosan coating were at their optimum point of maturity for 6 days. Fruits treated with a 1.5% chitosan coating were better for 12 days.
However, these samples also had uneven firmness once they were mature, as well as green and purple spots on the shell, which, according to the researchers, shows that the chitosan layer could be improved in the future.
Throughout the study, the researchers also took images of the entire surface of the fruits with hyperspectral cameras in the visible and near-infrared spectrum. The reflectance data from the images were then compared to the firmness, peel color, oxygen consumption, and weight loss of the avocados, using various computer models.
Two machine learning models better explained the changes that occurred during the ripening of avocados and were able to predict their remaining shelf life. The researchers say their chitosan-based prediction and coating technique could help improve the shelf life and quality of avocados for sale.
