ABSTRACT
PILOT SCALE WHEAT GERM STABILIZATION IN A SPOUTED BED
OYMAK, Mert Mehmet
M.S., Department of Chemical Engineering
Supervisor: Prof. Dr. N. Suzan KINCAL
Co-Supervisor: Dr. Cevdet Ö / ZTiN
April 2006, 97 pages
Wheat germ, a nutritionally rich by product of wheat milling, has poor
storage stability due to its content of essential fatty acids along with oxidative
enzymes. A pilot scale conventional spouted bed was designed and constructed as a
high temperature & / #8211 / short time treatment unit to bring about drying and roasting
effects. By facilitating the use of high temperature inlet air, yet maintaining the bed
solids at a temperature below the degradation temperature, spouted bed dryers
achieve thermal efficiencies unachievable by other dryers.
The inlet diameter, diameter of the column and the angle of the cone were 6.2
cm, 16 cm and 65° / respectively. Thermocouples were placed on the inlet, exit and
discharge gate of the column. Temperature profiles were recorded during drying,
roasting and cooling of wheat germ. The drying temperatures ranged between 201
and 243° / C, operation times between 6.5 and 12 minutes, and air flow rate between 55
and 65 m3/h. It was seen that the degree of roasting was closely related to the exit
temperature of the air. The exit air temperature range was determined as 155-160° / C.
Sensory evaluation tests were carried out. Wheat germ processed at 60 m3/h & / #8211 / 209° / C for 12 min and 55 m3/h & / #8211 / 216° / C for 7 min were selected as the samples for
storage studies, on the basis of the results of sensory evaluation tests. Reproducibility
runs were carried out for the selected conditions. The bed height increase study was
carried out at 60 m3/h & / #8211 / 240 to 243° / C. The processed and raw wheat germ was stored
in paper pouches at 40° / C, to estimate the shelf life on the basis of earlier studies.
Peroxide values of both raw and processed samples were followed during the
storage period. The initial peroxide values of raw germ, processed samples, and
reproducibility samples were 1.1 meq peroxide / kg oil. The peroxide value
formation data were found to follow zero order rate kinetics. Comparison of the
peroxide value changes in the processed and raw samples indicated that in the
studied range of 55-60 m3/h & / #8211 / 209-216° / C & / #8211 / 7-12 min, about 8& / #8211 / 10 fold increase in the
shelf life due to stabilization was achieved. The color parameters of each run were
determined using the CIELAB (L*, a*, b*) system. Total color difference (& / #8710 / E*)
values due to processing were calculated using L*, a* and b* values, to be between
2.3 and 58.6.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/3/12607153/index.pdf |
| Date | 01 May 2006 |
| Creators | Oymak, Mert Mehmet |
| Contributors | Kincal, Nazife Suzan |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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