An oxygen indicator dye formulation utilizing methylene blue has been developed based on various literature references. The formulation has been used to qualitatively demonstrate the oxygen barrier levels of four side sealed pouches made with various barrier laminations before and after retort processing. The method can be used to assess the barrier of the entire package and demonstrate areas of localized damage to the barrier. While all the materials showed good barrier before retorting some barriers were adversely affected by the retort process. EVOH coextrusions and SiOx coatings were the most adversely affected by retorting. Areas of defects in the adhesive lamination were detected that would not have been evident in conventional permeation testing. Permeation through the edge of the heat seal was also demonstrated by a fine line of colored dye just inside the seal area. The work to date has been on the qualitative observation of barrier levels but there is the potential for quantitative permeation measurement using colorimetric methods.
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