Egg washing using small-scale bucket washer

Abstract

The microbiological implications of using a small-scale bucket-style washer are reported for chicken eggs. On average, the bucket washer reduced the total bacterial numbers on the surface of eggs under manufacturer-recommended conditions from 5.36 log CFU egg^-1 to 2.82 log CFU egg^-1. No evidence of enhanced bacterial contamination of the egg contents was found when microbiological examination was undertaken a few hours after washing. When washing visibly soiled free-range eggs, there was a tendency for the wash-water to become dirty after only a few batches of eggs had been washed. Washing in dirty water could increase the numbers of bacteria on the surfaces of those shells which were visibly clean before washing. These additional shell-surface bacteria however, were not detected in the egg contents (n=1032), when analyses were undertaken 1–2 hours after washing. In contrast, when washed eggs were stored for 2 weeks at 15°C, we found that bacterial numbers in the egg contents were elevated when compared with unwashed controls. To determine if cool washing temperatures could cause water to taken up by egg contents, eggs were warmed to 37°C, 30°C, 25°C or 20°C and were submerged in aqueous protein stain at 15°C for up to 7 minutes. We did not observe take up of the stain solution unless its temperature was 15°C cooler than the egg contents and the eggs were immersed for at least 3 minutes.

Keywords::

• egg washing
• bacteria
• small-scale
• ingress
• storage
• temperature