DA-CVRC’s zero energy cooling chamber under on-station trial, shows promising results

Proper postharvest management of vegetables and fruits in the Philippines is in a haze. This is partially due to the multiple value chain players whose responsibility accounts for less and is unlikely to be affected by the deteriorating quality of vegetables and fruits when it reaches the consumers. 

Postharvest experts posit that freshly harvested fruits and vegetables should be handled under proper temperature and humidity conditions in order to maintain their good quality. This can be achieved through mechanical refrigeration which costs a lot, especially for smallholder farmers. 

To provide farmers with a cheaper alternative, DA-Cagayan Valley Research Center (CVRC) developed a non-refrigerated storage system for tomato, eggplant, and mango using the principle of evaporative cooling. 

“Zero Energy Cooling Chamber (ZECC) is an evaporative cooling system that can reduce ambient temperature and maintain high relative humidity. It requires no electric energy and is easy to construct,” explained project leader Mary Jane B. Ibarra. 

The chambers are cool because of the effect of evaporation. The evaporative cooling effect can be likened to our body perspiring. 

“Perspiration is a mechanism of our body to cool down our temperature. When we perspire, the droplets of water on our skin pores containing heat will evaporate; resulting in a cool feeling,” explained project proponent Homer P. Baun, Jr. 

He added, “The same principle [applies to] ZECC. When we pour water on the walling of the chambers, the cavity materials (coco coir, charcoal, double brick wall with river sand, and double wall with river sand and zeolite) will absorb moisture and in time evaporates resulting to a high relative humidity and lower temperature than outside.” 

For the on-station trials, DA-CVRC constructed four different chambers using various cavity materials for evaporative coolers: coco coir, charcoal, double brick wall with river sand, and double brick wall with river sand and zeolite. 

Commodities were also subjected to hot water treatment to maintain freshness. Various researches have proven that hot water treatment from 35°C and 63°C effectively inhibits ethylene production, delays ripenings, and reduces water loss during storage. It is also reportedly effective in preventing bacterial infection by activating the defense mechanism of cells. 

Results and analysis showed that ZECC using charcoal walling increased the shelf life and maintained the quality of tomato fruits until 31 days. This is comparable with ZECC using a double brick walling with river sand and zeolite, but constructing this kind of chamber is costly. 

ZECC using charcoal walling, double brick walling with river sand, and double brick walling with river sand and zeolite all showed comparable results in increasing the shelf life and maintaining the  quality of eggplants. However, DA-CVRC recommended ZECC using charcoal walling as it is cheaper compared to the other two setups. 

“Hot water treatment is effective but not always economically viable when storage time is just a few days. Based on the results, hot water treated fruits manifested significantly at day 20 for tomato and day 5 for eggplant,” explained Ibarra. 

“After the development of ZECC and on-station trial, this project will have an on-farm verification trial [using] the top two chambers with significant result in prolonging shelf life of tomato, eggplant, and mango,” she ended. (### Rena S. Hermoso)


For more information:
Mary Jane B. Ibarra
DA-Cagayan Valley Research Center
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