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United States Department of Agriculture

Agricultural Research Service

Research Project: POST HARVEST MEASUREMENT AND MANAGEMENT SYSTEMS TO IMPROVE PEANUT QUALITY AND US COMPETITIVENESS

Location: Peanut Research

Title: Capacitance and Phase Angle Measurement for Estimating Moisture Content in Nuts and Grain Nondestructively

Authors
item KANDALA, CHARI
item BUTTS, CHRISTOPHER

Submitted to: Proceedings of SPIE
Publication Type: Proceedings
Publication Acceptance Date: March 1, 2006
Publication Date: March 4, 2006
Citation: Kandala, C., Butts, C.L. 2006. Capacitance and phase angle measurement for estimating moisture content in nuts and grain nondestructively. Proceedings of SPIE. 617420-61420:1-8.

Interpretive Summary: Measurement of moisture content (mc) is an important aspect in the harvesting, storage, marketing and processing of agricultural products such as corn, wheat and peanuts. These products when freshly harvested may have a mc usually in the range of 20 to 40%. For trading, processing or storage the moisture levels for non-seed peanuts have to be decreased, to a recommended level below 10.5% wet basis. Reduction of the mc levels is obtained using both natural and artificial drying methods that involve considerable costs. During the drying process it is necessary to periodically measure the mc of the product. Drying for a longer time after the required mc level is reached, would not only increase the drying costs but also would lower the quality of the produce. The standard laboratory methods to measure mc of grain are tedious and take several hours. Instruments presently in use in the peanut industry work with bulk samples and with shelled and cleaned samples only. It may be useful to measure the mc in smaller samples and from physical measurements made on the in-shell peanut (pod) itself. This would save large amounts of edible peanuts from destruction but also the time required to shell and clean the peanuts. Earlier experiments showed a good correlation between the peanut pod and the kernel moistures. Thus, if the peanut pod moisture can be measured then the kernel mc may be estimated to an acceptable accuracy. In this article a portable electrical instrument for obtaining mc of in-shell peanut kernels is described. The measured mc values were compared with the values obtained by the standard air-oven method. This method can be used for similar mc measurements for grain such as corn and wheat. The moisture range of the peanuts tested was between 6% and 25% and the predicted mc values were within 1% of the air-oven bulk values for over 86% of the samples tested from the 2005 harvest. This method provides a basis for the development of a practical instrument that can measure mc of in-shell peanuts.

Technical Abstract: Measurement of moisture content (mc) is an important aspect in the harvesting, storage, marketing and processing of agricultural products such as corn, wheat and peanuts. These products when freshly harvested may have a mc usually in the range of 20 to 40%. For trading, processing or storage the moisture levels for non-seed peanuts have to be decreased, to a recommended level below 10.5% wet basis. Reduction of the mc levels is obtained using both natural and artificial drying methods that involve considerable costs. During the drying process it is necessary to periodically measure the mc of the product. Drying for a longer time after the required mc level is reached, would not only increase the drying costs but also would lower the quality of the produce. The standard laboratory methods to measure mc of grain are tedious and take several hours. Instruments presently in use in the peanut industry work with bulk samples and with shelled and cleaned samples only. It may be useful to measure the mc in smaller samples and from physical measurements made on the in-shell peanut (pod) itself. This would save large amounts of edible peanuts from destruction but also the time required to shell and clean the peanuts. Earlier experiments showed a good correlation between the peanut pod and the kernel moistures. Thus, if the peanut pod moisture can be measured then the kernel mc may be estimated to an acceptable accuracy. In this article a portable electrical instrument for obtaining mc of in-shell peanut kernels is described. The measured mc values were compared with the values obtained by the standard air-oven method. This method can be used for similar mc measurements for grain such as corn and wheat. The moisture range of the peanuts tested was between 6% and 25% and the predicted mc values were within 1% of the air-oven bulk values for over 86% of the samples tested from the 2005 harvest. This method provides a basis for the development of a practical instrument that can measure mc of in-shell peanuts.

Last Modified: 9/10/2014
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