Controlled atmosphere prolongs marketable life of mangoes

Philippine mangoes’ marketable life can now be extended for at least a month.

Thanks to the controlled atmosphere (CA) system developed through the project funded by the Department of Science and Technology (DOST) through the Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD).

The project is under the leadership of Dr. Ma. Concepcion Lizada of the Postharvest Horticulture Training and Research Center of the University of the Philippines-Los Baños (PHTRC-UPLB).

The CA system is a welcome development in view of the recent opening of the US market to Philippine mangoes. Currently, the ‘Carabao’ or ‘Manila Super’ mango has to be flown in to reach US stores in a marketable state. CA opens the possibility of sea shipments, not only to the US, but also to other distant markets like the European Union.

Dr. Lizada developed a CA systems that uses air cooled to 12.5 degrees centigrade, with oxygen level maintained at five percent. This is lower than the normal leveling air, which contains 12 percent oxygen.

Ethylene gas, which accelerates fruit ripening, is removed during CA to avoid fermentation, which renders the fruit unacceptable. "Earlier attempts at developing a CA system for mango have failed because of this problem," according to Lizada.

With the CA system developed by Lizada, most fruits can now be stored for four weeks, effectively delaying yellowing and softening. Full ripening after storage requires at least four additional days. At the table ripe stage, stored fruits are still acceptable.

In contrast, holding fruits at a temperature of 12.5 degrees centigrade without CA can effectively delay ripening for only about two weeks. Maximum benefit from CA can be obtained if fruits are sufficiently mature but green, free from injury, and subjected to storage as soon as possible after picking (i.e. less than two days after harvest).

Rotting limits the length of time that mangoes can be stored, thus, fruits have to be subjected to a 10-minute hot water treatment at 52 degrees-55 degrees centigrade, which effectively controls disease in ripening fruits.

"Other key factors that define success of CA for mango are timeliness of storage and good temperature management," Lizada added.

In commercial sea shipments, refrigerated container vans ("reefers") equipped with CA generators are utilized. CA generators make use of a membrane that retards the entry of oxygen into the systems, thereby reducing its level.

In a separate but related development, a multi-agency group from the private sector has validated the CA system developed in the DOST project, utilizing a commercial CA van. The commercial-scale trial demonstrated the favorable response of mangoes subjected to vapor heat treatment (VHT). VHT effectively eliminates the fruit fly as required by importing countries like Japan, the US, and Australia.

The DOST continues to put priority on mango and has provided funds for the development of appropriate technologies for this fruit. The Department’s S&T Action Program for Mango capitalizes on gains made in earlier projects like on the CA system. DOST-funded projects continue to generate information essential to quality assurance for the mango industry, covering production at the farm, all the way to processing. – S&T Media Service