Ready-to-Eat Egg Products Formulated with Nisin and Organic Acids to Control Listeria monocytogenes.

Formulating ready-to-eat (RTE) products with growth inhibitors minimizes the risk of listeriosis. In part I, RTE egg products formulated with 6.25 ppm nisin were evaluated to control Listeria monocytogenes. Individual experimental units were surface inoculated with 2.5-log CFU/g of L. monocytogenes, packaged in pouches with a headspace gas of 20:80 CO2:NO2, and stored at 4.4°C for 8 weeks. Formulations with finished product pH of 6.29 ± 0.07 limited growth to <2-log for 4 weeks. Products at pH values of 7.42 ± 0.12 and 7.84 ± 0.11 were not different (p > 0.05) from the control without nisin at pH 7.34 ± 0.13, all supported 4-log growth by 4 weeks. In part II, a nisin bioassay test was performed to evaluate the stability of nisin in eggs as affected by the product pH (6.00 ± 0.03, 7.00 ± 0.00, 7.50 ± 0.03, and 8.00 ± 0.02) and cooking to an internal temperature of 73.9 or 85°C for 90 s. The nisin activity loss increased as the product pH or the cooking temperature increased (p < 0.05). Part III evaluated the effectiveness of 6.25 ppm nisin in combination with either an acetate-based antimicrobial used at 1.0% (w/w) in egg formulation (A1.0), propionate at 0.3% (P0.3), acetate-diacetate at 1.0% (AD1.0), acetate-diacetate at 0.6% (AD0.6), and lactate at 2.0% (L2.0) as a positive control. These formulations had a finished product pH, moisture, and salt contents of 5.97 ± 0.21, 72.4 ± 0.9%, and 0.67 ± 0.05%, respectively. L. monocytogenes did not grow in formulations A1.0 and AD1.0, whereas L2.0 and P0.3 supported 2-log growth by weeks 6 and 15, respectively and AD0.6 supported <1-log growth over 20 weeks at 4.4°C. Evaluation of uninoculated control units in parts I and III showed no changes (p > 0.05) in the CO2 and O2 headspace gas composition, generally no detection or growth of background microbes, and no changes (p > 0.05) in the pH of the formulations during storage, all assuring absence of uncontrolled interferences for the growth of L. monocytogenes.

Replacing Corn and Wheat in Layer Diets with Hulless Oats Shows Effects on Sensory Properties and Yolk Quality of Eggs.

US organic poultry producers are under pressure to find feed alternatives to corn and wheat. Hulless oats offer advantages such as wide geographic adaptation of the plant and high concentrations of protein and oil in the grain. They have shown considerable potential in experimental work as a feed grain for poultry, but more research is needed into their influence on the sensory and nutritional properties of eggs. In this study, hulless oats were substituted for corn or wheat at 200 g kg-1 in diets fed to Hy-Line Brown hens and eggs were sampled for sensory evaluation after 8 weeks. Discrimination tests of blended and baked egg samples found evidence of difference between eggs from oat-based diets and those from the oat-free control (p < 0.05 for eggs from an oat-corn diet, p < 0.01 for eggs from an oat-wheat diet). Acceptance tests of similar samples showed that eggs from the oat-wheat diet were significantly less liked than control eggs for their texture (p < 0.01) and response to cooking (p < 0.01), while eggs from the oat-corn diet were somewhat less liked. Yolk weight was greater (p < 0.05) in control eggs (34.1 g) than eggs from oat-corn (31.6 g) or oat-wheat (31.2 g) diets, leading to smaller yolk proportion in the oat-fed eggs. Fatty acid profile differences across treatments were not of nutritional significance, and no evidence was found that the feeding of hulless oats improved storage properties of eggs. In this study, modifying the carbohydrate source in layer diets was shown to change textural properties of cooked eggs in a way that was perceptible to untrained consumers, probably by reducing the yolk proportion. This finding was not commercially relevant owing to small effect size, and results overall add to existing evidence that hulless oats can be fed to poultry at a moderate proportion of the diet with no negative effect on consumer acceptability of eggs. Regardless of the small effect size, however, findings are interesting from the food chemistry perspective because they provide novel evidence of how the thermal properties of eggs can be altered by a change in hen dietary carbohydrate source.