Non‐destructive packaging seal strength analysis and leak detection using ultrasonic imaging

Abstract

This study investigated the effectiveness of ultrasonic imaging for non-destructive assessment of seal strength in 335 ml polymeric trays. In the ®rst part of this study, the experimental procedures involved ®lling sample trays with beef enchilada, then sealing at temperatures of 170±260°C for 5 s at 3 bar. Ultrasonic measurements were conducted using an immersion technique in pulse/echo mode. The captured signal amplitudes of the re¯ections from the samples were digitized and analysed to construct high-resolution C-scan ultrasonic images of the seals. The acquired data were statistically analysed for each sample and used as a basis for comparison with the seal (peel) strength, measured as the energy at break. The energy at break was obtained from destructive peel strength analysis, performed using a tensile testing frame. In the second part of this study, ultrasonic imaging was used to predict the performance of the heat sealer used to fabricate the test trays by comparing the seal quality of each of the four quadrants of the samples trays. This study also investigated the minimum channel leak size that could be detected using this ultrasound system. The results of the peel strength analyses showed that a direct correlation exists between seal strength and sealing temperature (170± 227°C). Results of the ultrasonic imaging showed that the statistical scatter in the signal amplitude decreased as the sealing temperature increased. This reduction in the scatter of the signal amplitudes indicated a trend of increasing uniformity in the fusion of the two seal faces. Between 170°C and 193°C, sharp changes in the scatter were observed; however, little change was noted for sealing temperatures greater than 193°C, indicating that 204°C could be a minimum recommended sealing temperature. To con®rm this result, a drop test analysis was performed on trays ®lled with beef enchilada and sealed at temperatures of 170±260°C for 5 s at 3 bar. Results of this drop test con®rmed that 204°C was the minimum critical sealing temperature. Based on these results, ultrasonic imaging appeared to offer a promising non-destructive method for the prediction of seal quality in polymeric trays, sealing equipment monitoring and identi®cation of channel leaks 520 mm in diameter, and is comparable with the more established destructive peel strength analytical method.

Application of emerging technologies to control Salmonella in foods: A review

“…These include, extraction of aroma and other plant materials (Cocito, Gaetano, & Delfini, 1995), food freezing (Sigfusson, Ziegler, & Coupland, 2004;Zheng & Sun, 2006), inspection of food containers (Gan, Hutchins, & Billson, 2002;Griffin, Hull, & Lai, 2001;Pascall, Richtsmeier, Riemer, & Farahbakhsh, 2002), temperature monitoring (Haeggstrom & Luukkala, 2000), food characterization and analysis (Kulmyrzaev, Cancelliere, & McClements, 2000;McClements, 1995;Saggin & Coupland, 2001), and inactivation of microbes (Piyasena, Mohareb, & McKellar, 2003;Seymour, Burfoot, Smith, Cox, & Lockwood, 2002;USDA, 2000) and enzymes (De Gennaro, Cavella, Romano, & Masi, 1999), to name a few. A number of good published review papers are available on these aspects (Hauptmann, Hoppe, & Puttmer, 2002;Knorr, Zenker, Heinz, & Lee, 2004;Mason, Paniwnyk, & Lorimer, 1996;McClements, 1995;Piyasena et al, 2003;Povey, 1998;Samari, 1994;Withers, 1996;Zheng & Sun, 2006).…”

Development of a timesaving leak detection method for brick-type packages

“…After the seal was cooled, the wire was removed and a void from the inside to the outside of the package was created. This method of creating leaks in seals was similarly used by Pascall, Richtsmeier, Reimer, and Farahbakhsh (2002), Ozguler, Morris, and O'Brien (1999) and Song and Hargraves (1998). Voids created for this study were made using tungsten wires ranging in sizes of approximately 25, 50, 80, 100 and 150 lm in diameter and 6 mm in length.…”

Detection of seal contamination in heat sealed food packaging based on active infrared thermography

“…A major drawback of most testing methods currently used in the food industry is that they are destructive and can therefore only be applied to a subset of each production lot. Examples of destructive testing methods are burst-, peel strength-and dye penetration tests 1,6 . As an alternative, some non-destructive packaging inspection methods are described in literature.…”

“…Although human visual inspection is non-destructive and considerably fast, it still has several limitations. It is subjective and prone to human errors 6 . Moreover, visual detection of contamination in between the seal is limited to transparent packaging films.…”

“…Such online methods should be non-destructive, fast and contactless. Pascall et al (2002) presented a leak detection method based on ultrasonic imaging 6 . Defective seals were identified by Ostyn et al (2007) due to the abnormal vibration of the sealing bars during their production 2 .…”