Assessment of Methods for Walnut Water Content Determination during the Drying Process

Walnuts are a globally recognized tree nut known for their nutritional richness and versatility in culinary applications. The drying process is crucial in preserving walnut quality, preventing microbial growth, and ensuring a longer shelf life. Accurate measurement of water content plays a vital role in this process due to its impact on the overall quality of the nuts. This thesis aims to comprehensively assess Some methods for walnut water content determination, considering both traditional and advanced approaches, and to investigate rapid, low-cost, portable, and reasonably accurate techniques for measuring moisture. For this purpose, A sample of 30 walnuts was used for the experiment, their Moisture content (MC) ranges from 23.5% to 45.9% and their weight ranges from 17.4 to 31.6 grams. Samples were dried in the convection drying oven at 40 °C for 26 hours, and For MC determination, the walnuts were dried at 103 °C for an additional 16 hours to reach full drying state. The MC was then determined by the oven dry method as the direct method, and for the indirect method, Agreto PFM II baler-mounted moisture meter(capacitor)Dickey-John moisture forage moisture tester, and Sound moisture content detector were used. Agreto PFM II baler-mounted moisture meter, and DICKEY-John moisture forage moisture tester MC have been calibrated against oven dry method MC. The results showed Dickey John has a strong positive correlation between the two sets of measurements, with a high R-squared value of 0.9953, which suggests that the Dickey John readings are reliable but systematically lower. While the Agreto PFM II baler-mounted moisture meter had a lower R-squared value of 0.4241, indicating a weaker correlation with the standard method compared to the Dickey John meter. In addition, the results of Sound MC detector for the prediction and validation values, showed a positive correlation between measured and predicted moisture content, which is a promising aspect for a low cost and real-time method. Although the oven dry method shows high accuracy, it is time-consuming and costs a lot. Hence, according to this trial Dicky John and the Sound MC detector showed acceptable performance with time savings, real time measurements, and cost-effectiveness.