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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Quality & Safety Assessment Research » Research » Publications at this Location » Publication #321403

Research Project: Rapid Assessment of Grain, Seed, and Nut Quality Attributes with Microwave Sensors

Location: Quality & Safety Assessment Research

Title: Microwave moisture meter for in-shell peanut kernels

Author
item Trabelsi, Samir
item Lewis, Micah
item NELSON, STUART - Retired ARS Employee

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2016
Publication Date: 2/26/2016
Citation: Trabelsi, S., Lewis, M.A., Nelson, S.O. 2016. Microwave moisture meter for in-shell peanut kernels. Food Control. 66: 283-290.

Interpretive Summary: When the peanut crop is harvested, the kernel moisture content in the unshelled peanuts is too high, and the peanuts must be dried to a safe kernel moisture content of 10.49% moisture or lower for sale and safe storage. Current practice at peanut buying points requires sampling during drying and grading processes and shelling peanut samples before kernel moisture content can be determined with official moisture meters near the end of the grading process. If kernel moisture content then does not meet the required level, the peanut lots must be returned to the drying facility, and time and labor for grading is lost. Therefore, a moisture meter that could provide kernel moisture content from measurements on unshelled pod peanuts during drying and at the beginning of the grading process would permit substantial savings in time and money. A microwave moisture meter, built with off-the-shelf components, was developed, calibrated and tested in the laboratory and in the field for nondestructive and instantaneous in-shell peanut kernel moisture content determination from dielectric measurements on unshelled peanut pod samples. The meter operates at a single frequency of 5.8 GHz and uses free-space transmission measurement principles for determining the dielectric properties of the peanut pods. From these properties, a dielectric-based algorithm provides peanut kernel moisture content from the measurements on peanut pods. Field tests at a peanut buying station showed that moisture content of peanut kernels could be determined by the microwave moisture meter with an accuracy of about 0.8percent compared with the official moisture meter. However, when both the microwave and official moisture meters were compared with the standard oven-drying reference method for moisture determination, the accuracy of the microwave meter was about 0.5percent and the official meter was about 0.9percent moisture content. The microwave kernel moisture meter would help both peanut farmers and grading inspectors in making decisions with regard to moisture content at the farm and at buying points. In monitoring kernel moisture content during drying at the beginning of the grading process would provide significant cost and time savings. Also, it is expected that routine use of this meter during the grading process would improve peanut quality and consistency through more reliable moisture measurement. Other physical properties such as pod bulk density and pod moisture content can be determined with this microwave moisture meter from the same measurements on pod samples. Commercial availability of this microwave moisture meter would enable important savings and improvement in peanut quality for the benefit of farmers, processors and consumers.

Technical Abstract: . A microwave moisture meter built with off-the-shelf components was developed, calibrated and tested in the laboratory and in the field for nondestructive and instantaneous in-shell peanut kernel moisture content determination from dielectric measurements on unshelled peanut pod samples. The meter operates at a single frequency of 5.8 GHz and uses free-space transmission measurement principles for determining the dielectric properties of the peanut pods. From these properties, a dielectric-based algorithm provides peanut kernel moisture content from measurements on pods. Field tests at a peanut buying station showed that moisture content of peanut kernels can be determined with a standard error of performance (SEP) of 0.81percent when compared to the official moisture meter which required the pods to be shelled before kernel moisture content can be determined. When compared to the oven-drying standard method, values of the SEP were 0.53percent for the microwave moisture meter and 0.87percent for the official moisture meter.