Modification of NIR Instrument for Rapid and Nondestructive Determination of Chemical Content of Organic Material

Abstract

NIRS has been successfully applied to determine chemical content of various materials. However, the commercial NIR instrument can not measure many samples in one measurement time so the faster measurement can not be realized. The purpose of this research are (1) to modify NIR instrument designed by Budiastra et al. (1998) so it can be used to measure absorbance of some samples in one measurement time, and (2) to test the performance of the modified NIR instrument in measuring the absorbance of coffee. The modified NIR instrument consists of optical unit, electronic unit and mechanical unit (auto-sample holder). A new mechanical unit (auto-sample holder) has been developed to measure reflectance of some samples automatically. The performance of modified NIR instrument was evaluated by its consistency, delay time, detect ability for different water content and compared to other NIR instrument. The consistency of instrument is high with the percentage of homogeneity of 98.65%. The optimal delay of measurement is 200 ms. The modified NIR instrument is able to measure the different water content of coffee. The modified NIR instrument have same pattern of absorbance characteristic and higher than other NIR instrument, since the modified NIR instrument used integrating sphere and a large amplifier signal amplification.