Development of a Simple Portable Amylose Content Meter for Rapid Determination of Amylose Content in Milled Rice

Abstract

For amylose content determination in milled rice, currently, both the preparation method and the equipment used for amylose determination in milled rice are complicated and expensive. The method can only be applied in laboratory and carrying out the test in the field is not suitable. This paper proposes a modified rapid sample preparation procedure and a development of a simple, rapid, and portable device that is applicable for the prediction of the amylose content in rice. The device with a dimension of 170 × 220 × 80 mm and 600 g in weight was designed following the colorimetric method. The portable amylose content meter (PAC meter) consisted of a light source, filter, sample cell (using for input the starch–iodine complex solution as a result of reaction between amylose and iodine), phototransistor detector, and digital multimeter. Phototransistor detector was used for light intensity detection and it could generate current, and voltage was measured by digital multimeter. This device can measure both AC and DC (i.e., 9-V DC battery), allowing the device to be transported. The sample preparation procedure started from ten single kernels of milled rice that were boiled in the boiling water, cooled, and filtered followed by the addition of 0.1 M HCl solution and subsequently stained with iodine–potassium iodide. Next, the amylose–iodine complex was measured using the PAC meter. The regression model was developed based on the measurement of the amylose–iodine complex from the selected five rice varieties and used for the formulation of the standard curve for PAC meter. The regression model equation for the standard curve was established as amylose content (%) = (Absorbance + 0.036)/0.017 (R 2 = 0.99, p < 0.01). The amylose content of the samples was strongly and positively correlated with the absorbance values with 99 % correlation. Furthermore, to study the precision of PAC meter, 11 Thai rice varieties were selected (n = 10). The measurements made using PAC meter showed acceptable precision based on the international measurement system. The accuracy of PAC meter measurements was confirmed by comparing the results with those obtained by the conventional method, which was not significantly different (p < 0.05).The PAC meter is, therefore, applicable in the prediction of amylose content in rice, is of economical price, rapid, straightforward, portable, and reliable. In addition, this development can decrease the analysis period of over 24 h to less than 1 h.