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United States Department of Agriculture

Agricultural Research Service

Title: Non-Destructive Detection of Pits and Pit Fragments in Dried Plums

Authors
item Haff, Ronald
item Jackson, Eric
item Pearson, Thomas

Research conducted cooperatively with:
item Dfa Of California

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 12, 2005
Publication Date: October 15, 2005
Citation: Haff, R.P., Jackson, E.S., Pearson, T.C. 2005. Non-destructive detection of pits and pit fragments in dried plums. Applied Engineering in Agriculture.21(6):1021-1026.

Interpretive Summary: An inexpensive, non-destructive device was designed and built that can detect and remove dried plums that contain pits from the processing line in real-time. Dried plums were placed on a conveyor belt and compressed with two overhead rollers. The rollers were situated over the conveyor to form a gap smaller than pits but larger than would completely flatten the fruit. The first roller functioned to compress the meat of the fruit down to the size of the pit. The second roller was placed over a force transducer, which measured the amount of force applied to it when fruit was forced through the gap. This served to distinguish between pits and meat, as the pits were harder to force through the gap than the softer meat. The device was tested in a dried plum processing plant, and correctly identified 99.1% of pitted fruit and 75.3% of fruit with pits. The requirement to restrict the compression of the fruit to an amount that is non-destructive precludes the possibility to detect small pit fragments using this method. However, the cost of materials for the device was below U.S. $500, and therefore it is a potential method for use as a supplement to other technology currently in use to reduce the pit count in the final product.

Technical Abstract: An economical, non-destructive device was constructed to detect pits in dried plums. The device compresses the product between a roller and a force transducer, which detects the extra force generated when a pit is present. Two methods of classifying pitted fruit were developed, one based on the maximum magnitude of the compression force, and the other on analysis of the frequency spectra of the force transducer signal during compression. The accuracy of the former was 98.6% for pitted fruit and 69.4% for fruit with pits, vs. 99.1% and 75.3% for the latter. The second classification method was slightly more accurate, but more complex and costly to implement. The requirement to restrict the compression of the fruit to an amount that is non-destructive precludes the possibility to detect small pit fragments using this method. However, the cost of materials for the device was below U.S. $500, and therefore it is a potential method for use as a supplement to other technology currently in use to help reduce the pit count in the final product.

Last Modified: 8/27/2014
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