Update on PSE in Poultry Meat

Christine Z. Alvarado, Ph.D.

Department of Animal and Food SciencesTexas Tech University

Meat Quality

Attributes influenced by postmortem muscle metabolism:

Color

Water Holding Capacity

Texture

Ferket and Foegeding, 1994; Pearson, 1994

Pale, Soft, Exudative

accelerated postmortem glycolysis

protein denaturation

Hedrick et al., 1989; Lawrie, 1998

Meat Quality

Combination of events:

Rapid postmortem decline in muscle pH

High carcass temperatures (early postmortem)

Bendall and Wismer-Pederson, 1962; Penny, 1969

Meat Quality

Pale, Soft, Exudative Meat

Pale colorSoft textureLow water holding capacity

= reduced yields and poor quality

Meat Quality

Protein Denaturation

Myofibrillar proteins

Sarcomplasmic proteins

Bendall and Wismer-Pederson, 1962; Penny, 1969

Water holding capacity / gel strength

Color

Protein denaturation can cause low strength (poor) gels to form resulting in softer (mushy) texture.

Protein Denaturation

Example: Pale, SOFT, Exudative meat

Protein Denaturation

Poor slice ability

PSE meat

Deli Loaves and RollsMade with PSE Turkey Meat

Excessive Purge

Pale color

Low WHC

Problems with PSE Broiler Meat

Lost yield (sometimes hidden)

Problems in further processing equipment (e.g. automatic breast deboner)

Variation in color

Economic Implications

4The use of PSE meat in cooked products can cost a processing plant $2-4 million/year in lost meat yield alone.

4Estimate does not factor in:

hpackaging costshrework laborhmultiplier effect

PSE Incidence in Poultry

Ranges from 5-40%

20-25% is “background” (genetic?)

Remainder varies with day, week, or season (environment?)

Genetic and environmental factors not distinctly separated

Genetic EnvironmentalPSEAntemortemPostmortem

RyanodineReceptor (RyR)

Factors Influencing PSE Meat

Porcine Stress Syndrome

Hall et al., 1966; Harrison et al., 1968; Webb and Jordan, 1978; Fujii et al., 1991

genetic disorder (autosomal recessive)

linked to the ryanodine receptor gene

single point mutation

induced by halothane and succinylcholine

induced by stress

Malignant Hyperthermia in other species

The Ryanodine Receptor

Single Point Mutation

Fujii et al., 1991

Cytosine (C) to thymine (T) at nucleotide 1843

Substitution of cysteine for arginine in position 615

Abnormal calcium release

Observed in swine and humans – PSS/MH

No evidence to support or refute mutation in avian species

Halothane Screening

-

+

The Ryanodine Receptor

Isoforms

Mammalian

hα located in skeletal musclehβ located in cardiac muscle and brain

hα and β located in skeletal musclehGenetic difference found but currently being studied

Avian

Percival et al., 1994

Cassens et al., 1975; Backstrom and Kaufmann, 1995; D’Souza et al., 1998; Maribo et al., 1998

hRapid Growth hPreslaughter handling practiceshTransportationhEnvironmental temperatures

Stresses associated with PSE meat in swine

Poultry are subjected to similar conditions

Antemortem Stress Factors

Rapid Growth

Fast growing/heavier birds

Bohren et al., 1982; Sosnicki and Wilson, 1991;Hunt et al., 1999; Mahon, 1999; Mills et al., 1999

hhigher body temperaturehgreater metabolic heat productionhhigher mortality

More susceptible to heat stress

Greater incidence of muscle abnormalities

Muscles may outgrow life support system

Antemortem Stress Factors

Transportation

Physiologically stresses poultry

No increase in PSE incidence associated with 3 h of transportation prior to slaughter

May be dependent on duration and other conditions

Kannan et al., 1997; Freeman et al., 1984; Kannan et al., 1998Gregory, 1994; Cashman et al., 1989; Owens and Sams, 1999

Antemortem Stress Factors

McCurdy et al., 1996; McKee and Sams, 1997

Chronic heat stress

Higher incidence of PSE meat in turkeys

hlower muscle pHhhigher L* valueshhigher drip losshhigher cook loss

Heat stressed turkeys exhibited:

Postmortem Factors

Chilling Rates

Slow or inadequate chilling increases PSE

Problem in turkeys due to size

McKee and Sams, 1998; Alvarado and Sams, 2002; Alvarado and Sams, 2003

Postmortem temperature is the most important factor influencing overall meat quality

Objectives

To evaluate the relationships between muscle chilling rates, pH decline, color, water holding capacity, and texture, in turkey carcasses

To develop a time and temperature range for chilling turkey carcasses to decrease meat quality problems associated with PSE meat.

Materials and Methods

48 Male Nicholas Turkeys processed in 2 trials

Bled, scalded, picked, eviscerated

Chilled at 0, 10, 20, 30 C

Deboned

• Sample Analyses• Temperature of the fillets • pH • L* Value • Gel Strength • % CL • Expressible Moisture

Materials and Methods

Time Postmortem (min)0 20 40 60 80 100

Car

cass

Tem

pera

ture

(C)

26

28

30

32

34

36

38

40

420 C10 C20 C30 C

Temperatures of Turkey Pectoralis from Various Chilling Times and Temperatures

aa

b

b a

c

dPooled SEM = 0.43

pH of Turkey Pectoralis Chilled at Various Rates

Time Postmortem (min)0 20 40 60 80 100

pH

5.7

5.8

5.9

6.0

6.1

6.2

6.30 C10 C20 C30 C

a

bab

bab a

a

Pooled SEM = 0.02

5.72

5.76

5.8

5.84

5.88

5.92

5.96

24 26 28 30 32

Carcass Temperature (C)

pHMuscle Temperature and pH Decline from

Turkey Lobes

a a

b

b

Pooled SEM = 0.02

26 28 30 32 34 36 3852

53

54

55

56

57

58

Carcass Temperature (C)

L* V

alue

Relationship of Muscle Temperature and L* Value from Turkey Lobes

b

a a aPooled SEM = 0.31

Temperature ( C )

Parameter 0 10 20 30 Pooled SEM

L* Value (24 h)

51.85 51.47 51.50 51.45 0.20

Drip Loss 0.23b 0.24b 0.27b 0.40a 0.02

Cook Loss

14.72b 15.08b 14.61b 18.82a 0.60

Exp. Moist.

27.15 25.4 25.01 25.58 0.51

Gel Strength

17.31 16.01 15.67 15.65 0.69

abMeans with different superscripts are significantly different (P<0.05)

Means of Meat Quality Parameters for debonedturkey breast fillets

Conclusion

There is a chilling time and temperature relationship which can be a factor in the development of PSE meat.

Therefore, processors should implement a proper chilling regime in order to maintain acceptable meat quality.

Carcass Temperature recommendations

< 35 - 36 C at 0.75 h PM

< 28 - 30 C at 1.5 h PMAlvarado and Sams, 2003,2003

Strategies to Improve PSE Meat

Adjustment of pH or ionic strength

• use ingredients to restore protein function

• High pH phosphates (Pre-rigor and PM)• Increased pH• Decreased Cook loss• Improved color by 24 h PM3

Objectives

To determine the effects of pre-rigor marination with sodium phosphates on pH, color, and WHC in both normal and pale broiler breast fillets

Poultry Research Center (3h PM):• Injected (15% solution, 25 PSI)

pH 9 (0.9% NaCl, 0.45% PO4)pH 11 (0.9% NaCl, 0.45% PO4)

• Vacuum tumbled (25 mm Hg, 30 min, 14 RPM)• pH• Lab* value • Marinade pick-up/ retention • Cook Loss • Expressible moisture• Sensory• TBARS

Materials and Methods

pH(2h)

pH(24h)

L*(2h)

L*(24h)

EM(%)

CL(%)

Normal 6.30a,x 6.12a,y 49.57b,x 49.19b,x 18.58b 22.38a

Pale 6.09b,x 6.00b,x 53.79a,x 51.38a,y 22.65a 24.09a

PooledSEM

0.03 0.02 0.40 0.27 1.34 0.60

Measurements from Normal and Pale Fillets Marinated with a pH 9 Solution

a, bMeans in a column differ ( P < 0.05)x, yMeans in a row and within the same parameter differ (P < 0.05)

pH (2h)

pH (24h)

L* (2h)

L* (24h)

EM (%)

CL (%)

Normal

6.30a,x

6.28a,x

49.87b,x

48.63b,x

17.94b

20.29a

Pale

5.95b,x

6.22a,y

53.86a,x

50.39a,y

24.47a

20.99a

Pooled

SEM

0.04

0.02

0.48

0.21

1.19

0.97

Measurements from Normal and Pale Fillets Marinated with a pH 11 Solution

a, bMeans in a column differ ( P < 0.05)x, yMeans in a row and within the same parameter differ (P < 0.05)

Sensory Measurements from Marinated Fillets

Hedonic Scale ValueTreatment

3.42pH 11

3.44pH 9

TBARS Measurements from Marinated Fillets

4.464.171.99pH 11

3.73.921.76pH 9

TBARS (Day 4)

TBARS (Day 2)

TBARS (Day 0)

Normal

3.934.062.07pH 11

4.783.222.17pH 9

TBARS (Day 4)

TBARS (Day 2)

TBARS (Day 0)

Pale

Shelf-life Measurements from Marinated Normal Fillets

Log

CFU

/ml

2

3

4

5

6

7

8

Day 0 Day 3 Day 6 Day 9

1 4

Shelf-life Measurements from Marinated Pale Fillets

2

3

4

5

6

7

8

Day 0 Day 3 Day 6 Day 9

pH 9 pH 11

Log

CFU

/ml

Conclusion

High pH phosphatesIncreased pHDecreased Cook lossImproved color by 24 h PM

Impacts to industry: higher yield, increased consumer acceptability

Strategies to Improve PSE Meat

Sort meat based on color or meat pH

• direct PSE meat to “non-problem” products

• away from products with no or low amounts of salts and phosphates

Sorting Breast Fillets

Based on Color

• easy and rapid• human eye• optical scanning equipment

Based on Meat pH

• more complicated• currently used in pork and beef industry

Conclusions

Long-term strategies

• genetic typing• screening tests• selective breeding

Short-term strategies

• reduce environmental stress• sort meat• control flow/distribution of PSE meat

Questions?

Christine Alvarado, Ph.D.International Center for Food Industry Excellence

Animal and Food SciencesTexas Tech University