THE EVALUATION OF DRYING KINETICS AND WATER ACTIVITY OF RADISH SPROUTS PROCESSED BY DIFFERENT DRYING METHODS
1
WULS-SGGW, Institute of Food Sciences
2
University of Valencia, Faculty of Pharmacy, Nutrition and Food Science Area
3
Sorbonne Universites, University of Technology of Compiègne, Integrated
Transformations of Renewable Matter Laboratory
4
Shiraz University of Medical Sciences, Division of Food and Nutrition, Burn
and Wound Healing Research Center
Publication date: 2021-06-07
2019;(598):29-39
KEYWORDS
ABSTRACT
Radish sprouts are rich in bioactive compounds and usually consumed as raw or slightly cooked. Due to their high water activity, they are perishable and the microorganisms can grow very easily. Moreover, sprouts have been associated with numerous foodborne outbreaks worldwide. Thus, there is a need to develop efficient methods to preserve all the healthy valuable compounds and limiting the contamination of sprouts
with foodborne pathogens. One of the ideas is to use drying as one of the oldest methods of food preservation. However, the high temperature of traditional drying negatively influences the quality of agricultural products and this process is energy-intensive. The different methods of drying can be used in order to shorten the drying time and improve the quality of dried plant tissue. The aim of this work was to compare the drying kinetics of different drying techniques such as convective drying (air-drying, CD), microwave-assisted convective drying (MV-CD) and infrared-assisted convective drying (IR-CD) of radish sprouts. Convective drying was conducted using temperature of air equal to
60°C and airflow set at 1 m·s –1 . Microwave-assisted convective drying was set on microwave power equal to 200 W, the airflow 1 m·s –1 and the temperature was equal to 30°C. In infrared-assisted convective drying was used the power of infrared emitter equal 7.875 kW·m –2 , and airflow was set at 1 m·s –1 . Fresh radish sprouts contained 88.64% of water and their water activity was equal to 0.94. Drying time was calculated as the time necessary to reach a moisture ratio equal to 0.0014. The shortest drying time (92 min) was noted for the convective drying compared to infrared-assisted (127 min) and microwave-assisted (152 min) air-drying methods. The highest value of drying rate was noticed for
the samples dried by the convective method. For microwave-assisted convective drying and infrared-assisted convective drying rates were reduced by 45.2% and 27.6%, respectively. After the drying process, water content was reduced to the range of 4.53–5.65%, whereas water activity was reduced to the range of 0.330–0.401. This means that all of the dried products exhibited water activity below 0.6 which ensures their microbiological stability and improves the safety of radish sprouts.
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