The present work examines the antimicrobial efficacy of the essential oils of thyme, oregano and carvacrol against L. monocytogenes biofilms produced on stainless steel coupons and for control of L. monocytogenes growth on raw catfish fillets stored at 4°C for 10 days. At 0.5%, all three essential oils were highly effective in completely eliminating L. monocytogenes cells from stainless coupons within 24 h as compared to the untreated control yielding ~7 log CFU/cm2 L. monocytogenes. When catfish inoculated with L. monocytogenes were dipped for 30 min at 4°C in essential oil solutions of thyme and oregano at 1%, 2% and 5%, there were no significant reductions in L. monocytogenes counts on the fresh catfish fillets as compared to untreated control. For the same conditions, treatment with 2% carvacrol resulted in a complete reduction of 4 log CFU/g of L. monocytogenes counts from fresh catfish fillets.

Edam and Cheddar whey were thermized (T) for different time periods (5–30 min) at 70 degrees Celsius, vacuum evaporated, and spray dried to obtain whey powders (WP). Native and thermized WP were evaluated for antioxidative properties. Edam and Cheddar WP significantly reduced thiobarbituric acid-reactive substances (TBARS) and peroxide value (PV) in ferric-catalyzed soybean oil emulsions. Thermization significantly improved antioxidative properties of WP with 5T, 10T, and 15T treatments showing better protective effects compared to 20T and 30T treatments. Based on these results, native (0T) and thermized (5T, 10T, and 15T) Edam and Cheddar WP coatings, with and without enzymatically hydrolyzed casein (CH), were used to reduce oxidative degradation and moisture loss of cubed beef steak and pork loin. Thermized treatments significantly reduced TBARS and PV in both types of meat, with CH containing treatments showing enhanced antioxidative properties. Protein oxidation as reflected by carbonyl formation and a decrease in sulfhydryls was also reduced by thermization. Treated and native WP coatings significantly reduced moisture loss of meat samples. Cubed beef steak treated with Cheddar WP coatings were evaluated for microbiological quality and basic sensory attributes. Although not statistically significant, 5T, 10T, and 10TCH treatments numerically showed potential for microbial reduction up to 4 days of storage. Sensory evaluation showed significant protection of key sensory attributes by treatments throughout the storage period when compared to controls with the 5 min thermization showing the best effect on lowering offlavor development based on sensory scores. The effect of pH and glucomannan (GM) on antioxidative properties of thermized (5T) Cheddar WP coatings applied to catfish fillets was also investigated. Coatings at pH 7.0, 7.5, and 8.0 (with GM) showed markedly greater protection against oxidative degradation compared to coatings without GM, as reflected by TBARS values and PV after 7 days of storage. Carbonyl formation and oxidation of sulfhydryl groups were also significantly reduced by coatings containing GM. Cheddar WP-based edible coatings (pH 7.0–8.0) with GM markedly reduced lipid oxidation and protein oxidation of fresh catfish fillets.