Research articles
ScienceAsia 46 (2020): 52-58 |doi:
10.2306/scienceasia1513-1874.2020.004
Flow-based titration with a colorimetric detection box
using a smartphone for the determination of titratable
acidity in coffee
Sarawut Somnam*, Miki Kanna
ABSTRACT: Acidity is one of the key components for coffee quality which could be determined by titration. However,
the endpoint observation with bare eyes might give error because of the dark color of coffee. Although this problem
could be solved by using a pH meter, the calibration and maintenance processes including the cost of the device may be
the drawbacks. In this research, a digital image colorimetric detection system was established with economic devices.
The caption of image was carried out by a smartphone under the control of light intensity and focus range in a homemade detection box to assess the primitive color (red/green/blue or RGB) data from the color change of an acid-base
indicator. In addition, to make process more comfortable and reduce the detection time, the flow-based technique was
also applied to the setup for the signal monitoring process. The method was highly reproducible with %RSD less than
1 (n = 11) and detection time of 24 s was achieved. From the analyses of roasted coffee beans, the results obtained
agreed well with those from the potentiometric standard method.
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Department of Chemistry, Faculty of Science and Technology, Chiang Mai Rajabhat University, Chiang Mai
50300 Thailand |
* Corresponding author, E-mail: sarawut_som@cmru.ac.th
Received 18 Apr 2019, Accepted 22 Dec 2019
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