2. muscle to meat SDL Flashcards
(27 cards)
What factors contribute to the presentation of dark, firm and dry beef (DFD) also known as dark cutting beef (DCB)?
Combination of factors that stress the animal and deplete glycogen stores in muscle:
- rapid fluctuations in temperature
- excessive use of growth promotive implants
- genetic factors
- rough handling
- bulls have more dark cutters than steers, cows or heifers
What factors contribute to the presentation of pale, soft exudate (PSE)?
- Rough handling causes overheating of the pigs
- rough handling and electric prods also cause increased lactate levels which damage meat quality
- poor chilling causes internal temperature of pig meat to drop too slowly
- pig genetics - pigs with a positive PSS (porcine stress syndrome) gene
- In spring - water temperature increases
How can DFD be prevented?
- Don’t mix strange cattle together prior to slaughter at the plant (to prevent fighting)
- Handle animals quietly and reduce or eliminate prod usage
- Unload trucks promptly
- Cattle should not be held overnight in the stockyards of the plant
How can PSE be prevented?
- Provide adequate pen space in holding pens at the plant
- During hot weather wet animals down with sprinklers
- Allow 2-4 hours of rest prior to stunning
- Handle and drive quietly and reduce or eliminate electric prod use
- Never fill pens more than one half to three quarters full
- Access to water
- Measure levels of lactate in blood to monitor handling in stunning area
What problems result of DFD?
- Economic losses (reduced market value)
- Quality issues (appearance - dark, texture and taste - tougher and stronger off-putting flavour due to high pH levels, reduced shelf life - High pH can interfere with the curing process)
- Processing problems (water - holding capacity - higher water-holding capacity, challenges in curing and smoking - higher pH can interfere).
What problems result of PSE?
- Economic losses (reduced market value - meat is less desirable due to poor appearance and texture, often sold at a lower price, increased waste - higher rates of meat rejection and trimming)
- Quality issues (appearance - meat is pale and unattractive , texture, moisture loss - meat is soft and exudates a lot of moisture and can can become dry and tough when cooked, poor binding - protein structure is compromised leading to poor binding in products like sausages and ham)
- Processing problems (yield and efficiency - high moisture loss during processing, poor emulsification - in products that require emulsification e.g. sausages, PSE can cause issues with fat and water binding. Shelf life (spoils easily due to exudative properties)
what does it mean that the slaughterhouse dresses the carcasses according to European Union (EU) specifications in pigs?
Before weighing the carcase, you must remove the:
- tongue
- bristle (hair)
- hooves
- genital organs
- flare fat
- kidneys
- diaphragm
Why is 2% of carcase weight deducted?
Calculating the cold weight requires a 2% deduction on top of the deductions that are made when calculating warm weight
What does it mean when a pig carcase is classified as ‘E’?
A grade (SEUROP) refers to the lean meat as a percentage of recorded carcase cold weight.
Grade E - 55% or more but less than 60%
What is the typical outbreak investigation scenario involving broiler chickens?
• A Salmonella outbreak affects humans (e.g., children in Rutland)
• Two potential sources: poultry abattoir or open broiler farm (e.g., ‘Blackwater Open Farm’)
• Investigators must sample both sites, use microbiological methods to detect Salmonella, and perform typing methods to determine strain similarity and outbreak linkage.
What are the key questions guiding the investigation?
Presence/absence: Is the pathogen there? Prevalence: How widespread is it? Source attribution: Where did it originate? Risk: What is the threat to public health? Typing choice: What typing/genotyping techniques best answer the questions?
What equipment is needed for conducting a zoonotic disease outbreak investigation?
• Sampling equipment: sterile swabs, peptone water, faecal pots
• PPE: gloves, masks
• Transport: cool boxes, documentation
• Lab tools: incubators, selective media, PCR machines, ELISA kits, serotyping reagents.
What are the sample handling and transport regulations (EU Regulation 200/2012)?
• Samples must be collected aseptically
• maintained at 4°C during transport
• processed within 48 hours
• clearly labelled
• and traceable with proper documentation.
What sample types are typically collected in poultry-related investigations?
• Faeces
• carcass swabs
• feed and water
• bedding/litter swabs
• slaughterhouse equipment
• carcass rinse
• meat surface swabs
• cloacal swabs.
How do you isolate Salmonella from samples?
• Pre-enrichment in buffered peptone water
• selective enrichment (Rappaport-Vassiliadis or Selenite broth)
• plating on XLD or Hektoen agar
• incubation at 37°C
• colony identification via biochemical tests
• and confirmation by typing.
How are pathogens enumerated from farm/food samples?
• Plate Count (CFU)
• Most Probable Number (MPN)
• membrane filtration
• qPCR for DNA copy number
• and direct microscopic count.
What is serotyping and how is it performed?
• Serotyping detects surface antigens (O, H) by mixing bacterial suspension with specific antisera
• Agglutination indicates a positive result
• Fast and specific, but expensive and lacks strain-level resolution.
What is genotyping and why is it important in tracing pathogens?
• Genotyping uses DNA analysis to distinguish bacterial strains
• Includes PCR, WGS, PFGE, and MLST
• Provides high-resolution source tracking during outbreaks.
How does PCR work in outbreak investigations?
• PCR amplifies specific DNA targets
• It is sensitive, rapid, and specific but cannot distinguish live from dead cells and only samples small genomic regions.
What is PFGE and when is it used?
• PFGE cuts bacterial DNA with rare enzymes, separates fragments on a pulsed gel, and creates a DNA fingerprint
• Highly accurate but expensive and labour-intensive.
What is phage typing?
• Tests bacterial sensitivity to a panel of bacteriophages
• Generates unique profiles, but sensitivity may vary and requires expert interpretation.
What is whole genome sequencing (WGS) and what are its benefits?
• WGS reads the entire DNA sequence of an organism
• Extremely accurate, allows creation of phylogenetic trees, but expensive and requires bioinformatics support.
What is the IMViC test and what does it assess?
• Biochemical test panel (Indole, Methyl Red, Voges-Proskauer, Citrate) to differentiate coliforms
• Easy and low-cost but lacks strain specificity.
What are the key requirements for transporting samples in a zoonotic outbreak investigation?
• Samples must be transported aseptically
• Must be kept at 4°C to prevent bacterial overgrowth or degradation
• Samples should be processed within 48 hours
• Ensure accurate labelling and traceability
• Avoid contamination during handling and transit.
