Transducer detects fruit pits.

To make sure that those who enjoy sweet, succulent prunes don't crunch down on the fruits' pits, USDA-ARS researchers have devised and patented a new way to detect them. As the dried plums roll along a processing line's conveyer belt, a roller gently presses the fruit against the belt. A force transducer mounted beneath the belt reads the amount of resistance the roller encounters. This information is transferred to a signal processor linked to a computer.

Using a mathematical formula, the computer can determine whether the reading likely indicates the presence of a plum pit or fragment. If so, the signal processor alerts a sorter to remove that plum from the processing line for retesting. Lab tests have shown that the system signals false positives only 1% of the time, so researchers are now working toward increasing its running speed. This pit-detecting system has potential for checking other dried stone fruits, including peaches and apricots. The cost of materials for the device is less than $500. It has potential to supplement to other technology currently in use to help reduce the pit count in the final product.

Actually, the researchers had developed two methods of classifying pitted fruit. One was based on the maximum magnitude of the compression force used, and the other on an 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, compared with 99.1% and 75.3% for the latter.

The researchers have also developed an algorithm using a Bayesian classifier to automatically detect olive fruit fly infestations in x-ray images of olives. The ability of the algorithm to differentiate infested and non-infested olives was tested. Internal damage to the olive was a factor in detection. Slight damage was correctly identified 50% of the time, and severe damage correctly identified 86% of the time. Non-infested olives were correctly identified with 90% accuracy.

Further information. Eric Jackson, USDA-ARS Western Regional Research Center, Plant Mycotoxins Research Unit, Room 0100, 800 Buchanan St., Albany, CA, 94710; phone: 510-559-8868; fax: 510-559-5777; email: ejackson@pw.usda.gov.