Discoloration of cured meats in the retail case is a concern for prepackaged sandwich manufacturers, resulting in negative consumer perceptions of quality and freshness, and decreased purchase intent. The introduction of Modified Atmosphere Packaging (MAP) has significantly improved color appearance and increased the refrigerated shelf life, but it has not eliminated cured meat discoloration from developing. Consumer demand to see the product has led to greater product exposure to light, resulting in cured meat discoloration via photooxidation. The mechanism of photooxidation of cured meats is not fully understood, and there are multiple factors to consider including package variables (residual oxygen, Oxygen Transmission Rates (OTR), and product to headspace ratio), storage and display conditions (frozen followed by refrigeration, light exposure), and challenges created by the combination of bread, meat and cheese for a 30 day refrigerated shelf life in order to find practical, cost effective solutions for the prepackaged sandwich industry that are acceptable to the consumer. Using a bestselling ham & cheese sandwich variety in conjuncture with a 80% N2/20% CO2 Modified Atmosphere Package, a number of potential solutions are evaluated including ferrous and nonferrous based oxygen scavengers, UV (ultraviolet) blocking films, ham formulations and LED vs. fluorescent lighting to understand the impact to cured meat color scores in the form of L*and a* color measurements, visual appearance, and residual oxygen over time. Solutions demonstrating visual improvements or better color stability on L* or a* color values are presented to consumers for preference and input. The results of the study show that Ferrous based oxygen scavengers have potential, but challenges are created when used in a frozen storage and distribution system followed by refrigerated display. While predicted a* values in a scavenger/MAP packaged ham are higher (more red) over time compared to MAP only, the high variability found in initial meat color, compounded by variability in package oxygen content and changing conditions in the package over time results in no statistical differences due to predicted overlapping a* rate constants. The impact to L* (lightness and darkness) values are measurable and correlate with observed consumer preferences, but inconsistent throughout the refrigerated shelf life, with the potential for scavenger sachet packaged ham sandwiches to develop low L* (darkening) values that are unacceptable to the consumer. As a result, consumer preference for sandwiches with and without an O2 scavenger is inconsistent at different days throughout the shelf life. Consumer input on active packaging reveals the need for further understanding of acceptance in a retail environment where the demand for fresher products continues to grow. While unaided, the sachet is initially unnoticed by consumers implying acceptance, awareness of its presence leads to concerns over freshness. The added cost of a scavenger requires recovering lost sales of 80,000 sandwiches per year, but brand perception also needs to be considered. Grey tinted ferrous based scavenging film was not accepted and viewed as an attempt to hide qualities of the food. Consumer demand for higher quality ham with full muscle appearance and texture along with the many unknown factors in cured meat pigment formation and photooxidation mechanism makes ham reformulation not a practical approach. Use of LED lights and UV blocking films in the UV range of 366 – 400 nm that is detrimental to meat pigments did not result in improved color scores or visual appearance, validating that visible light is as equally destructive to meat color. As a result of this study, no changes are recommended to the current MAP package in a frozen storage and distribution with direction for future studies provided.
University of Minnesota M.S. thesis. September 2015. Major: Food Science. Advisor: Theodore Labuza. 1 computer file (PDF); liv, 628 pages.
Investigation of practical hurdle technologies for preventing photooxidation of cured lunch meats in prepackaged sandwiches.
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