Chitosan coating and imaging technique enhance avocado shelf life and quality

Avocados, beloved for their versatility and flavor, often present a challenge due to their short shelf life. However, researchers from ACS Food Science & Technology have made strides in addressing this issue. They have developed a chitosan-based coating that effectively preserves avocados for extended periods. Additionally, they have devised an imaging technique that rapidly predicts the fruit's remaining shelf life.

Traditionally, people determine an avocado's ripeness by gently squeezing it, looking for a slight sponginess. Producers also employ similar methods to assess which avocados can withstand transportation to stores. Despite these efforts, some avocados still spoil prematurely.

To combat premature ripening, researchers have explored the use of compounds like 1-methyl-cyclopropene (1-MCP). More recently, studies have shown that chitosan, a naturally derived biomaterial obtained from shellfish exoskeletons, exhibits antimicrobial properties when applied as a fruit coating, including on avocados. In light of these findings, Angie Homez-Jara, Angelica Sandoval-Aldana, and their team sought to compare the efficacy of these two preservation methods on avocado quality and shelf life.

The researchers subjected commercially mature Hass avocados to treatment with gaseous 1-MCP or water-based solutions containing varying concentrations of chitosan. To mimic real transportation conditions, both treated and untreated avocados were chilled at 41 degrees Fahrenheit for 21 days before being transferred to room temperature, simulating a grocery store , until they spoiled.

Untreated samples and those treated with either 1-MCP or a 1% chitosan-based coating remained at optimal ripeness for 6 days. Avocados treated with a 1.5% chitosan-based coating maintained their quality for 12 days. However, these samples displayed uneven firmness upon ripening and exhibited green and purplish spots on the peel, indicating room for improvement in the chitosan coating.

Throughout the study, the researchers used hyperspectral cameras operating in the visible and near-infrared spectrum to capture images of the entire fruit surface. Reflectance data from these images were then compared to the avocados' firmness, peel color, oxygen consumption, and weight loss using various computer models.

Two models provided the best explanation of the ripening process and accurately predicted the remaining shelf life of the avocados. The researchers believe that their chitosan-based coating and prediction technique could significantly enhance the shelf life and quality of avocados available for sale.

Source: American Chemical Society

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