The Philippines can now meet the world demand for dried mangoes. Through the newly engineered drying technology that uses combined far-infrared and convection heating (FIRCH) system, dried mango processors can now double-up their production.

After two years of laboratory and pilot-scale research, PHilMech engineers found out that the two-stage drying technique using FIRCH significantly reduced the drying time of mango slices from 12 hours to just eight hours.

Far-infrared is now increasingly used worldwide in various food processing systems because of its efficiency in heat transfer. And in mango drying industry, this would be the first in the Philippines.

Mango Drying

According to the Food and Agriculture Organization (FAO), the country is one of the top 10 producers of mango in the world. The Philippines claims to have the world’s sweetest mango-"and that is the Philippine Carabao Mango. Thus, Philippine mango, either fresh or processed, has been in demand in the export market.

During the peak harvest season, local processors are constrained to meet the growing demand of dried mango export market due to the limited drying capacity. In Cebu, wherein the most number of dried mango processors could be found, mango drying through convection dryer such as cabinet dryer heated by LPG or steam boilers is common practice.

Convection dryer is suitable for mango drying because in the drying process the circulating heated air cannot easily damage the sensitive mango slices; it consumes a longer drying time though. Mango slices can not stand high temperature for a long period because of risks of case hardening (undesirable phenomenon wherein the outer surface is already hard while the inside remains soft) and made it more complicated by the added syrup before drying.

Nb> Rapid Dryer

The team of Dr. Romualdo Martinez and Engr. Robelyn Daquila, both experts in drying, initiated the research to find solution to the lengthy mango drying. This led to their discovery on the use of far-infrared.

The pilot-scale unit dryer is tunnel shaped and made of food grade stainless steel with a dimension of 9.6 meters in length, 0.38 meter in width, and 0.38 meter in height. It uses ceramic heaters to produce infrared energy with temperature of 250°C.

Because of the sensitivity of the mango slices on high temperature, Dr. Martinez and Engr. Daquila found out that far-infrared could be still used through intermittent exposure. Using a conveyor, mango slices are moved slowly at the rate of 4-6m/h and in the process it will be heated through far-infrared for three minutes. The mango slices will undergo seven intermittent drying and cooling cycles and requires two hours for 40 trays of mango slices to partially dry. The moisture content is reduced from 60 percent down to 40 percent. According to the researchers, this is the optimum length of exposure that the mango slices can handle, otherwise, the surface of the product will burned.

Two-stage Drying

Still, there’s a need to dry the semi-dried mango slices to convection dryer to completely reduce the moisture content down to 14 percent. And the good news is, this will only consume six hours in the cabinet dryers.

"The mango slices will just spend six hours at the cabinet dryer, 50 percent is saved on the drying time in the convection dryer. This means a 100 percent increase on the usage of the dryer; the production output of the cabinet dryers will be then doubled," Engr. Daquila explained referring to the two-stage drying system with the FIRCH technology as the first stage dryer and cabinet dryer for the second stage.

Another significant result of their research is that the FIRCH can have 30 percent savings in overall energy consumption and the 17 percent reduction in energy cost compared to convection method alone.

In a sensory evaluation conducted by the College of Home Science and Industry at the Central Luzon State University, the FIRCH-dried mango has no significant difference with the commercially available dried mango. There is no difference on the sweetness and sourness, aroma, texture, firmness and moist appearance of the products.

Interestingly, the Food and Nutrition Research Institute of the Department of Science and Technology conducted nutrient analysis on the product of FIRCH system. It was found out that the product’s beta carotene is higher by 15 percent compared to conventionally dried.

bTechnology Demonstration

Recently, a technology demonstration was conducted among the mango industry players in Cebu. "Many showed interest on FIRCH during our techno-demo. We also gathered some ideas that could greatly improve our technology," Engr. Daquila added.

According to him, the capacity of the far-infrared conveyor dryer can be customized to fit with the capacity of the existing convection dryers of the processors. The FIRCH technology is set for commercialization this year.

Mango Drying R&D

Through the years, mango drying technologies developed by PHilMech is evolving near optimum efficiency. Engr. Robelyn Daquila started it all with the adaptation of the Multi-Commodity Solar Tunnel Dryer. This was followed by the development of mango cabinet dryer with biomass-fed-furnace which was pilot-tested in 2006. These two dryers are now commercially available.

Still, with the discovery of FIRCH, PHilMech engineers continue to improve the mango drying industry through the development of more efficient dryers.

"If drying process will be quicker and the products are of high quality, this will be a big help to the processors and to the mango farmers too," added Engr. Daquila.