The oven-drying method for determination of water content in Brazil nut

Abstract

The official methods adopted by different worldwide agencies for determination of water content of Brazil nut is the dissication in drying oven at 105 ºC during 3 or 24 hours and dissication until constant height of samples. However, applying these methods for Brazil nut, may result in inconsistent values, possibly due to lipid oxidation. Thus, the objective of this study was to evaluate the accuracy of the oven-drying methods, recommended by the official agencies, and to determine the oven-drying correct parameters, such as temperature and exposure time. For this purpose, samples were placed in drying ovens set at 85, 90, 95 and 105 °C and weighed hourly, between 3 and 12 hours and after 24 hours of exposure, and the results were compared to Karl Fisher titration, considered as a reference method in this study. The temperature of 105 °C, for any exposure time, resulted in overestimated water content compared to reference method. However, there was no difference between the water content values obtained by oven-drying assay at 90 °C for 6 hours and by the reference method, allowing to conclude that the determination of water content in Brazil nut samples, in drying oven under these conditions, can be performed with the same accuracy and precision of the Karl Fischer method.