Functional Bioactivity and Sensory Attributes of Off-season Mango Influenced by Postharvest Chitosan Coating

In the humid corners of southern India, a unique agricultural rhythm plays out alongside the familiar summer harvest. While most mango trees rest after their main crop, specific varieties in this region bear fruit again during the off-season, stretching from October through January. This extended harvest offers a rare chance for farmers to sell their produce year-round, but it comes with a significant hurdle: the monsoon rains. Mangoes are naturally short-lived fruits that soften and rot quickly, a problem that becomes even more acute when the weather is wet and warm. To keep these fruits fresh, scientists often look for ways to slow down the fruit's natural aging process without using harsh chemicals. One promising approach involves edible coatings made from chitosan, a substance derived from the shells of crustaceans. This material is safe for humans, biodegradable, and known to form a thin, protective film that can regulate how the fruit breathes and loses water, potentially acting as a shield against spoilage.

Researchers at the Central University of Tamil Nadu set out to test how well this natural coating could protect the off-season 'Rumani' mango, a variety prized for its availability during the rainy months. They gathered mature fruits from an orchard in Nagapattinam and divided them into groups. Some fruits received no treatment at all, serving as a baseline, while others were dipped in solutions containing different amounts of chitosan: zero percent, half a percent, one percent, and one and a half percent. After dipping, the fruits were allowed to dry and then stored in cardboard boxes at typical room temperatures, mimicking the conditions they would face in a market or a home. Over the course of sixteen days, the team carefully monitored the fruit, checking for signs of decay, measuring how much weight they lost, and testing their texture, taste, and nutritional value.

The results showed a clear difference between the treated and untreated fruits. The mangoes that received no coating began to show signs of spoilage earlier and lost their firmness quickly, reaching a fully ripe, soft state by the end of the storage period. In contrast, the fruits coated with the highest concentration of chitosan, at one and a half percent, remained firm and fresh for the full sixteen days. This protective layer acted as a semi-permeable barrier, slowing down the fruit's internal breathing rate and reducing the production of ethylene, a natural gas that signals fruit to ripen. Because the fruit was not rushing to ripen, it retained more of its natural acidity and vitamin C, and it lost less water to the surrounding air. The researchers found that the uncoated fruits and those with lower concentrations of the coating deteriorated faster, with the half-percent group spoiling completely by the fourteenth day, likely because the acid used to dissolve the chitosan had weakened the fruit's skin rather than protecting it.

Beyond just keeping the fruit from rotting, the coating helped preserve the qualities that make mangoes enjoyable to eat. The team measured the sweetness, the firmness, and the levels of antioxidants, which are compounds that help protect the fruit and provide health benefits to people who eat it. The mangoes treated with one and a half percent chitosan maintained higher levels of these beneficial compounds and a better texture than the others. When a group of people tasted the fruit at the end of the storage period, they rated the one-and-a-half-percent coated mangoes highest for their green color, aroma, and overall appeal. The uncoated fruits, having ripened too quickly, were less favored. The study suggests that applying this specific concentration of chitosan creates a modified environment around the fruit that delays the aging process, allowing the mango to stay fresh longer without the need for synthetic chemicals. This simple, natural intervention could help farmers and retailers extend the market life of off-season mangoes, ensuring that these fruits remain available and high-quality even during the challenging monsoon season.