6. PSE, DFD — principle of formation, explanation of biochemical process

Question 1

Characteristics of PSE and DFD meat:

Answer 1

pH value
< 5,8
> 6,2
Water holding capacity
poor
very good
Consistency of meat
soft
solid
Colour of meat
pale, light
dark
Post-mortem glycolysis
very fast
slow and incomplete
Shelf-life of meat
slightly reduced
significantly reduced
Tenderness of meat

Question 2

1) Pale, soft, exudate (PSE)

Answer 2

= defective type of meat
- more common in Landrace, Pietrain and cross breeds of these breed: they are genetically prone
to stress
- porcine stress syndrome:
- RYR-1 gene mutation of ryanodine-receptor which is the sarcoplasmic reticulum calcium- release channel
- can do genetics test prior to breeding —> pigs usually homozygote
- unsuitable for processing of ham or smoked meat
- combination of 2 factors:
- low pH value shortly after slaughtering:
- stressful situations prior to slaughter —> pigs produce lactic acid from glycogen
anaerobically —> lactic acid + fast post mortem glycolysis —> rapid drop in pH - electrical stunning also speeds up post mortem glycolysis
- high temperature within meat (>37°C) at the same time
- unusual appearance is caused by high temperature of meat (42°C) + low pH = denatured
proteins
- in some countries 20-40% of pork meat is PSE meat

Question 3

Detection of PSE meat

Answer 3

• checking the pH 45 min or 60 min after slaughter —> should be 5,8-6,8 60 min post slaughter - < 5,8—> severe PSE
• check m. longissimus dorsi
• no point in checking it at 24h as the pH value will be the same in normal pork and PSE pork

Question 4

Characteristics of PSE pork

Answer 4

• reduced water holding capacity & WBC:
  PSE meat seems wetter than normal pork even though the water content is the same
  when cooked it loses all water and becomes dry
• lighter colour: myofibrils loose volume —> increased ability to scatter light
• once proteins are denatured no additive can make up for the shortcoming: denatured proteins
  leads to the softness
• non-functional proteins can’t be turned back into their native state

Question 5

Preventative measures

Answer 5

• mainly to decrease stress
• green/blue light in holding areas is calming to pigs
• keep areas well-lit as pigs will walk towards them more readily
• carbon dioxide is better than electric stunning
• chill quickly in blast freezer: can cause slight cold shortening but still better than PSE

Question 6

2) Dry, firm, dark (DFD)

Answer 6

• predominantly in beef & lamb, sometimes seen in pigs
• unsuitable to use for raw meat products e.g. fermented raw sausages
• causes:
• usage of glycogen in an aerobic pathway when exposed to stress and most commonly seen in tired animals:
• energy is burned but no lactic acid is produced
• most commonly seen in young bulls with depleted energy sources
• insufficient decline in pH value within meat after slaughter:
• in beef after completion of rigor mortis (48-72hrs post slaughter) the pH is >6,2 - normal pH 5,2-6,4 48-72 hours post slaughter
• no release of enzymes —> decrease in the tenderness

Question 7

Characteristics of DFD meat

Answer 7

• incomplete rigor mortis
• dark in colour: large, dark myofibrils —> decrease in ability to scatter light
• slight slimy appearance (“the meat does not come off the knife”)
• high protein solubility
• excellent water holding capacity: due to large myofibrils
• shelf life is shortened: because without the pH drop the DFD meat is highly susceptible to
  microbial spoilage

Question 8

3) Laboratory tests

spectrophotometric

Answer 8

• spectrophotometric determination of meat colour: - pale in PSE and dark in DFD
• represents the reflection of light
• normal: 13-25%
• PSE:>25%
• DFD:<13%
• pH determination:
• sample: lean meat without fat and tendons from fore quarter or hind quarter —> m.
  longissimus dorsi, m. semimembranosus
• place electrode directly into the muscle tissue and measure twice —> calculate the mean

Question 9

3) Laboratory tests

- determination of free water content:

Answer 9

• determination of free water content:
• lowinPSEandhighinDFD
• method: drip loss
• normal drip loss: 1-5%

Question 10

National legislation Czech Decree 289/2007 Coll.:

Answer 10

• meat edible after heat treatment not for health reasons with mark until it has been treated
• heat treatment: 70°C for 10 min or an equivalent