INSPECTION OF SEAL INTEGRITY OF FOOD PACKAGES USING ULTRASOUND AND PRESSURE DIFFERENTIAL TECHNIQUES

Abstract

Food packages undergo incubation and inspection to ensure that packages are sealed tight and protect the foodfrom contamination and spoilage. Over the years many inspection techniques are used with varying degrees of success. Withthis study, two techniques, ultrasound and pressure differential technique, were assessed and the effectiveness of thesetechniques was quantified. Noncontact, immersion type ultrasonic testing in pulse/echo mode using high frequency soundwaves was evaluated for use in defect detection in the seal area of semirigid cups and polymeric trays. At disparities withinthe seal, sound waves generated by 20MHz ultrasonic transducer were reflected back to the receiver. Received ultrasonicsignals, or echoes, were used to develop Ascan and Cscan presentations. Discontinuities in the seal, short seal, nonbondedareas, imbedded foreign matter such as wire and Teflon in the seal, contaminated seal, and abrasion were detected usingultrasound based on reduced signal strengths.Integrity of mealsreadytoeat (MRE) pouches was inspected using a new pressure (vacuum) differential technique. Thistechnique is based on a threestep approach. To evaluate the system, air was linked into a test chamber through a calibratedneedle valve simulating a leak at different leak rates. A simulated leak that generated values higher than reference, anddependant upon the leak rate, was accepted or rejected by the leak tester. The technique proved to be effective, although,shortsealed nonvacuum packed pound cake pouches failed during subsequent leak testing.