STUDY OF SOLIDS LEACHED DURING RICE COOKING USING THE TRANSMITTANCE AT 650 NM

ABSTRACT The objective of this research was to develop a method to predict the amount of total solids leached during rice cooking using light transmittance at 650 nm with an ultraviolet‐visible spectrometer. Rice was cooked in excess water for different durations, the transmittance was measured, and the solids were determined gravimetrically after evaporation of the water. Results of leached solids obtained gravimetrically showed a good correlation with the logarithm of the transmittance (R2 = 0.9731), thus indicating the feasibility of the method. As a result, calibration curves were developed using rice starch and rice flour as standards. Calibration curves generated with rice starch has shown to overpredict the amount of solids leached. When rice flour was used, the method predicted that the solids leached with an average error of 2.3%, with a minor tendency towards underprediction. PRACTICAL APPLICATIONS During the industrial production of instant rice, important amounts of solids leach out from the rice, producing yield loss and high biochemical oxygen demand (BOD) waste streams. A quick method to estimate the leaching potential of different rice varieties would be important to adjust processing parameters and minimize leaching. The results presented in this study show that the transmittance at 650 nm can be used to estimate the solids leached during rice cooking. Still, the successful implementation of this method depends on the finding of suitable standards.