Prolonging the storage life of minimally processed tropical fruits

Minimally processed fruits have become more visible in the Philippine market, whether in supermarkets or wet markets. Aside from being fresh, nutritious and inexpensive, they do not require preparation or cooking which makes them more attractive to local consumers. However, fresh-cut fruits have shorter shelf life compared to their whole, unprocessed counterparts. The damages incurred during processing promote wound-induced ethylene production that leads to rapid deterioration. These physiological changes may be accompanied by a loss of desirable fruit flavor, discoloration of the cut surface, loss of color, decay, increased rate of vitamin loss, rapid softening, shrinkage and a shorter storage life. One of the main problems as well in fresh-cut quality and shelf life is the high spoilage rate associated with microbial contamination.

Introducing an ethylene antagonist such as 1-methylcyclopropene (1-MCP) gas into fruit packs can be a potential method of 1-MCP application to maintain the storage quality or extend the shelf life of such products. As an ethylene antagonist, 1-MCP inhibits ethylene action by binding strongly to ethylene receptors in plant tissues. It has a non-toxic mode of action and negligible residue and is active at very low concentrations. It is also chemically similar to naturally occurring substances. Although 1-MCP has been registered in 27 countries for use on fresh fruits and vegetables, in Southeast Asia, it is still being tested on fresh produce.

1-MCP gas being injected into the fruit packs (Photos by James Bryan Gandia and Meryl Bernardino)

The Emerging Interdisciplinary Research Grant project of Dr. Katherine Ann C. Israel and her team from UP Los Baños investigated the response of different tropical fruits to the application of 1-MCP. They found that in general, 1-MCP is effective in improving the storage quality of fresh-cut tropical fruits by controlling ethylene production. But the kind of fruit and type of packaging also affect the response. Bacterial growth is significantly retarded when the ‘Sinta’ papaya, a hybrid cultivar popular in the Philippines and with good potential for fresh-cut production, is placed in a plastic tray then wrapped with stretchable film than when stored in a clamshell tray. The post-cutting application of 1-MCP on fresh-cut ‘Queen’ pineapple, a cultivar locally known as the Formosa variety and has a crispy texture with a very sweet taste, packaged in a polypropylene tray overwrapped with stretchable film delays color changes but does not maintain general visual quality. With ‘Carabao’ mango, considered the sweetest mango in the world, 1-MCP slows down the development of water-soaking in fruit flesh slices. However, it does not help with browning. As for the white dragon fruit, 1-MCP not only hinders browning and microbial contamination and improves visual quality and water-soaking but it also considerably increases the fruit’s antioxidant activity.

Pineapple slices after three days of storage. Left: control; Right: 1-MCP treated. (Photos by James Bryan Gandia and Meryl Bernardino)

The team also studied the response to 1-MCP gas application of vegetable packs used for salads and typical Filipino dishes.

For this work, the group received the Invention Disclosure Incentive, an award given by the University to researchers who report the existence of a project or invention with patent potential.