Process of heat treatment and changes in garlic properties
University Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: kic@tf.czu.czs
Abstract:
This paper aims to present the results of research focused on the heat treatment of garlic (Allium sativum) into black garlic. The research compared three varieties of classic kitchen garlic (Dukat, Topaz and Sabagold), grown in the Czech Republic. The course of heat treatment in a hot air dryer was investigated at 60 °C. Changes in the weight and moisture of the samples were monitored gravimetrically for 78 days. The dry matter content was measured gravimetrically after drying at 105 °C. There were certain differences between the varieties studied. The intensive decrease in water content, dry basis u (g g-1) during the first 20 days was the fastest in the Topaz variety, when it dropped below 0.4 (g g-1) after only 9 days. In the Dukat and Sabagold variety water content, wet basis w (%), from the original values w = 62 to 66% dropped below 30% within 20 days, and in the Topaz variety below 20%. Changes in the colour of garlic cloves were measured by A CM-600d spectrophotometer. During the black garlic processing, its gradual darkening occurred. Lightness L* decreased in the Dukat variety from 80.39 to 27.47, Topaz from 78.29 to 29.09 and Sabagold from 83.64 to 28.72. In all varieties, colour changes occurred. Greenness (-a*) changed from the 9th day to a redness (a*) whose saturation gradually decreased. The yellowness (b*) of all varieties also decreased significantly.
Key words:
CIELAB system, colour, garlic, heat treatment, Maillard reaction, moisture, spectrophotometer, temperature