Technical gazette, Vol. 20 No. 1, 2013.
Original scientific paper
A contribution to the development of moisture measuring of vacuum-dried hygroscopic materials
Ante Čikić
; Technical College in Bjelovar, Trg Eugena Kvaternika 4, 43000 Bjelovar, Croatia
Ivan Samardžić
; J. J. Strossmayer University of Osijek, Mechanical Engineering Faculty in Slavonski Brod, Trg Ivane Brlić Mažuranić 2, 35000 Slavonski Brod, Croatia
Antun Stoić
; J. J. Strossmayer University of Osijek, Mechanical Engineering Faculty in Slavonski Brod, Trg Ivane Brlić Mažuranić 2, 35000 Slavonski Brod, Croatia
Abstract
Dehydration of hygroscopic materials, especially fruit (blueberries, blackberries, raspberries, etc.) and some types of vegetables in vacuum dehydrators by means of radiation at low temperatures preserves their original quality and medicinal value. Experimental research has been carried out, whereby the moisture reduction of vacuum-dried blueberry fruits was measured by applying the capacitive measuring method, in order to check the method and contribute to possible development of applicative devices. A real vacuum chamber with radiating plate electric heaters and additional functional and regulation equipment was used. Measuring sensors were projected and made, and a measuring device was assembled and programmed. By changing very low values of capacitance, the possibility of measuring moisture reduction in blueberry fruits during drying was confirmed. A close connection between the regulation precision of working parameters (subpressure, temperature) in the chamber and the accuracy of measuring the material moisture was underlined. By using an interdigital sensor acceptable sensitivity in measuring the moisture of dried material was achieved. Guidelines for further research and possible development of an applicable measuring device were suggested.
Keywords
blueberry; capacitive measuring; drying by means of radiation; interdigital sensor; moisture measuring; vacuum chamber
Hrčak ID:
97491
URI
Publication date:
22.2.2013.
Visits: 2.226 *