Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 26, 2005
Publication Date: July 28, 2005
Citation: Allende, A., Mcevoy, J.L., Luo, Y., Artes, F., Wang, C.Y. 2006. Effectiveness of two-sided UV-C treatments in inhibiting natural microflora and extending the shelf-life of minimally processed ‘Red Oak Leaf’ lettuce. Food Microbiology. 2:241-249.
Interpretive Summary: A wide variety of packaged fresh-cut salads are available to consumers today, including mixed salads containing the popular 'Red Oak Leaf' lettuce. A major factor limiting the shelf-life of such packaged salads is microbial growth. In addressing the need to limit microbial growth on these products we examined the use of a known anti-microbial energy, ultraviolet light. Various doses of the ultraviolet light were applied to both sides of freshly processed 'Red Oak Leaf' lettuce. Following packaging and storage of the product, microbial growth and quality aspects of the product were determined. All doses of the light tested reduced microbial growth with the higher doses of the light being the most effective. However, tissue damage resulting in a loss of quality of the product occurred at the higher doses of the ultraviolet light. We concluded that ultraviolet radiation at the proper doses could be used by lettuce processing plants to reduce microbial growth on 'Red Oak Leaf' lettuce without adversely affecting quality of the product. This information could benefit the fresh produce industry that is involved in marketing fresh-cut lettuce, as well as foodservice organizations and consumers that desire high quality produce with an acceptable shelf-life.
Fresh processed 'Red Oak Leaf' lettuce (Lactuca sativa) was exposed to three doses of ultraviolet-C (254nm, UV-C) radiation (2.36 kilojoules per square meter, 4.74 kilojoules per square meter and 14.22 kilojoules per square meter). The UV-C radiation effects on microbial growth chemical composition, and sensory quality were evaluated. All three doses reduced growth of microorganisms tested in this study (total aerobic bacteria, Enterobacteriaceae, lactic acid bacteria, and yeasts) when compared with the control. UV-C treatments used in this experiment had little or no effects on sugar or organic acid content of the lettuce. The highest dose induced tissue softening and increased browning after 7 days of storage at
5 degrees C. The 4.74 kilojoules per square meter treatment and lower doses reduced the microbial growth without damaging the product tissue. It was concluded that UV-C radiation at proper doses could reduce microbial loads without adversely affecting quality of 'Red Oak Leaf' lettuce.