Hygiene and safety of shell eggs Flashcards
Internal structure of eggs
Outside to inside
- shell - has pores for gas exchange
- shell membrane - contains antimicrobial peptide
- thin albumen - “
- thick albumen -“
- Vitelline membrane
- Yolk- where things (such as bacteria) can grow
evolution of eggs
have evolved to be a non perishable item - due to chick not emerging for 21 days
Spoilage of eggs
From
Moulds - through the shell pores and grows on them
Pseudomonas- would make it glow fluorescent and smell bad
Bacillus - smells bad
shell contaminants
will be slow to penetrate the egg
storing eggs in the fridge will slow protein breakdown and they will resist microbial growth better
cuticle around shell will provide protection by selling the pores
if eggs are washed like in America cuticle is replaced by soap, wax, oil or cactus juice
Preservation methods
sodium silicate - an alkaline solution that will keep eggs over winter - keeps shell clean and stops bacterial growth
lime water - does a similar thing
Salmonella in eggs
mainly Salmonella enteric server Typhimurium - cause typhoid in mice
associated with dirty/ wet egg shells - contaminate the outside of eggs
Vehicles of infection
Raw egg
Undercooked egg
contamination is more likely in mass produced food - catering
salmonella has managed to make its way through the yolk where it can multiply there
Salmonella spp. as a human pathogen
Primarily associated with poultry and eggs
risk of death is up 3 times greater in the year post- infection
Sustained infection of food animals
Evolution of salmonella
E.coli and salmonella had a common ancestor till they diverged
E.coli to mamas
Salmonella to egg laying things
e.g. dinosaurs, raptors, turtles, birds etc.
enterica species infects birds and now there is 2000+ servers
enterica is pathogenic for mammals
Turtles and salmonella
Have evolved to internalise salmonella and spread to any cold blooded animals
Handling them = spread
Control in production systems
reduced chance of infection
- biosecurity - mixing outdoors and indoors = biosecurity ruined
- feed hygiene/ additions
- Rodent control - salmonella was originally used in pesticides so mice carry lots of salmonella/ typhoid in mice
options are more limited in extensive systems
VACCINATE
Vaccinations
laying hens - can vaccinate against enteritidis* and tychomurium - both servers of salmonella
broilers - used for meat and only like for 5 weeks so not enough time to mount an immune response
Caged hens and salmonella
- not going outside - less exposed to rodents - cortisol at low levels as not trying to promote adaptive behaviour
moving to enriched - will start competing for supplies so cortisol levels will increases body is trying to adapt- will mean immune system is less good so will shed more salmonella
Invasive salmonella
Most salmonellas usually stays in the gut
here contamination by
- fecal contamination of carcasses in scald tanks
- contamination of eggs
Salmonella enteritidis* is naturally invasive - won’t stay in the gut
Egg shells becoming salmonella positive
Egg shells can become salmonella positive at lay
not how SE enters the egg contents
Salmonella Enteritidis infections in chickens
instead of staying in gut will migrate to the oviduct an colinises in the ova
SE will cause inflammation in oviduct - will cause release of more ovum so more eggs - survival strategy - economically good?
In most hens SE is subclinical
Statutory controls in the UK
Enteritidis and Typhimurium are the only serotypes of salmonella that are regulated - as adapted to eggs and related to lots of lines
slaughter of the infected is no longer necessary
- egg must not go directly for human consumption
- will be a class B egg - for things that will be cooked or pasteurised
National control program for salmonella
samples must be taken if you produce eggs for a commercial basis
- only for large scale commercial buisnesses
Flock does not need testing if
- Production is for private domestic use- is not entering the market
- fewer than 350 hens and supplies the consumer direct e.g. farm- gate sales
British lion eggs
Code of production of eggs for large consumers
all are vaccinated so eggs are much safer
Protection from salmonella
- National control plan
- vaccination
- not sending eggs from salmonella contaminated flocks for class A human consumption
