Published in Journal of Applied Packaging Research, Volume 3, Issue 1, January 1, 2009, pages 1-14.
The purpose of this study was to determine the feasibility of using biodegradable films suitable for fresh-cut lettuce with commercial vertical-form-fill-and-seal packaging machines (VVFS) equipped with heat-sealing bars. Biodegradable high-density polyethylene (BHDPE) and polypropylene (BPP) films were tested. Commercial bags of pre-cut Romaine sealed in a polyethylene/oriented polypropylene (PE/OPP) bag formed on a WFS machine were used as the control. All bags were held at 4.4°C, 80% RH and assessed for reduction in quality during storage per a commercial (in-house) standard utilized by a large pre-cut salad packer in Salinas, California. When the biodegradable films were sealed with a VFFS machine equipped with a thermal-bar heat sealer, a 52.5% fail rate was observed due to the non-continuity of the seals. Leaks were found when bags were vacuum tested to 14 in Hg absolute for 15 seconds. However, a 45.5% fail rate was also observed for commercial bags made using the same VFFS machine, suggesting similar seal concerns for current industry film structures. Though an attempt was made to only store bags that were sealed properly, bags made from the biodegradable films sealed with the thermal-bar did not perform as well as the commercial packages and the shelf-life of the pre-cut Romaine was shortened. When biodegradable bags were sealed using a bar impulse sealer, hermetic seals were obtained. The Romaine stored in these bags had a similar rate of decay and level of pinking after 14 days storage as Romaine packaged in the commercial PE/OPP bags. These results indicate that the use of commercial impulse sealers, rather than thermal-bar heat sealers, would allow industry to utilize these biodegradable films for pre-cut lettuce mixes.
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