Inspection of seal integrity of food packages using ultrasound and pressure differential techniques
2001
Ayhan, Z. | Zhang, Q.H. | Farahbakhsh, B. | Kneller, M.
Food packages undergo incubation and inspection to ensure that packages are sealed tight and protect the food from contamination and spoilage. Over the years many inspection techniques are used with varying degrees of success. With this study, two techniques, ultrasound and pressure differential technique, were assessed and the effectiveness of these techniques was quantified. Non-contact, immersion type ultrasonic testing in pulse/echo mode using high frequency sound waves was evaluated for use in defect detection in the seal area of semi-rigid cups and polymeric trays. At disparities within the seal, sound waves generated by 20-MHz ultrasonic transducer were reflected back to the receiver. Received ultrasonic signals, or echoes, were used to develop A-scan and C-scan presentations. Discontinuities in the seal, short seal, non-bonded areas, imbedded foreign matter such as wire and Teflon in the seal, contaminated seal, and abrasion were detected using ultrasound based on reduced signal strengths. Integrity of meals-ready-to-eat (MRE) pouches was inspected using a new pressure (vacuum) differential technique. This technique is based on a three-step approach. To evaluate the system, air was linked into a test chamber through a calibrated needle valve simulating a leak at different leak rates. A simulated leak that generated values higher than reference, and dependant upon the leak rate, was accepted or rejected by the leak tester. The technique proved to be effective, although, short-sealed non-vacuum packed pound cake pouches failed during subsequent leak testing.
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