A tomato without the edible coating (left) and another with the coating (right) in room ambient condition after 30 days. Credit: Kona Mondal

A biodegradable, edible coating solution can extend the shelf-life of fresh produce, such as green chillies and tomatoes1, 2. The coating can reduce the load of food-borne pathogens, retain firmness, and prevent the weight loss of fruits and vegetables when stored for a month.

This coating will reduce post-harvest loss significantly, says a team at the Indian Institute of Technology Guwahati in Assam.

The scientists synthesised the coating solution by mixing de-oiled crude ethanolic extract of a marine green alga with a chitosan-based solution. They made dried, edible films from the coating solution and found that this film was thermally stable, blocked ultraviolet and visible light, and showed antioxidant properties.

The researchers, led by Vimal Katiyar, dipped fresh, green chillies in a coating solution at room temperature. The coated green chillies maintained fresh appearance with a minimal weight loss after seven days in storage.

The chillies showed minute changes in colour, indicating a delay in respiration and senescence, and a prolonged shelf life. The coating also retained the shiny appearance of tomatoes, even after 20 days in storage, and extended their shelf life by a month. The researchers say the coating protected the cells of the tomatoes by slowing oxidation and decay.

The team found that the coating also protected sliced and whole potatoes, apples and strawberries. The coating can be spread on fresh produces using a cheap and simple dip-coating technique, and can even be converted into a vegetable storage pouch, they add.