Browsing by Subject "Drying kinetics"

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Erklärung der Strukturbildung und Trocknungskinetik von Einzeltropfen im Ultraschall-Levitator
(2022) Hülsmann, Ramona; Kohlus, Reinhard
In recent years, acoustic levitation has been increasingly used to investigate individual particles during the drying process. In this process, a droplet is positioned in a standing ultrasonic field in such a way that non-contact observation can take place. Within the scope of this work, an experimental setup for a levitator was designed and the drying and levitation behavior of various substances was investigated.
Foam mat drying of cassava and associated properties : comparison between white-flesh and yellow-flesh varieties
(2021) Ayetigbo, Oluwatoyin Elijah; Müller, Joachim
Cassava is an important staple food crop in Africa, Asia and Americas, serving as food, raw material, feed, and source of livelihoods. However, cassava has poor post-harvest physiological stability, deteriorates rapidly, has high toxic cyanogenic contents and poor physicochemical properties. Foam mat drying was considered as a technique to combat these challenges. First, a comparison of the different properties of variants of cassava based on colour was made from the perspective of sustainability. Afterwards, an optimization of the foaming process was conducted for two varieties (white-fleshed and yellow-fleshed) of cassava using various foaming variables. Optimal variables were not different between both varieties. Foaming reduced cyanogenic toxicity and retained carotenoids in cassava significantly, but also had significant influence on colour. The foams developed had asymmetrical distribution in air bubble diameter, while foam powder microstructure showed close association between the hydrocolloids and starch. Furthermore, an optimization of the drying conditions of optimal cassava foams was conducted based on temperature and foam thickness. Drying kinetics (moisture removal ratio, diffusivity, dying rate) of the cassava foams and the effect of various drying conditions on selected physicochemical properties of cassava foam powder was researched. Two falling rates were found during drying, Diffusivity was significantly affected by temperature but not foam thickness. The cassava foam powders had acceptably low cyanogenic contents, and had high retention of carotenoids. Foam powder microstructure did not change significantly with temperature, but yellow cassava foam powder had higher coalescence.