PENGUJIAN SISTEM PENGERINGAN BAWANG MERAH (Allium ascalonicum) DENGAN CARA PENGASAPAN

n the effort to improve the existing ways for handling post harvest of red onion among current farmers, where these old ways are giving unsatisfying results (high damage rate), we were designed a drying building facilitated with fumigation equipment. The building is having area of 2 x 3 m2 with 3 m height of pre-cast brick (batako) wall and with pyramid-formed roof.

The drying space of this dimension can be filled by approximately 1.25 tons of wet red onion. This building is equipped with heat exchanger forming from ceramic pipe sized 23 cm in diameter. The ceramic pipe is perforated with 3 cm in holes diameter in order to conduct fumigating process toward stored red onions. The heat is resulted from burning stove placed in the inlet of heat exchanger. This testing activity is financed by University of Gadjah Mada through Research Department.

Testing for drying building equipped with fumigating system was conducted at Sangkeh hamlet of Srigading village in Sanden district of Bantul Regency. This testing is intended to find out the performance of the building. From the testing conducted by means of interrupted drying method, it is known that at the applied drying temperature of approximately 37oC this building is capable to decrease 46% water content of red onion, i.e. from 68% into 22% at surrounding temperature of 29oC and relative humidity of 90% during 70 hours of period time.

Temperature change during drying process is varied depending on position measured from the bottom of building and stated in square relationship, i.e. T = 1.25 h2 – 4.25 h + 38.7; likewise, the decrease in material masses, which was

formulated as follow: S = 0.49 h2 – 2.52 h + 17.32, is faster than conventional drying method. For the quality of end product, comparing with conventional method, the application of this system is giving uniform results. The cost of drying by means of fumigation method is depending on fumigating time or on average amounted to Rp19.62 hourly for every kilo of wet red onion. Moreover, application of this fumigating system is increasing the profit received by farmers on average amounted to Rp5,525,252.93.