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PH Values of Breast Meat

Effect of Sex, Age and Live Weight on the PH Values of Breast Meat in Broiler Chickens

Published: December 22, 2011
By: Mostafa Elsabbagh (Lebanese University)
pH value is the negative logarithmic activity of the hydrogen ion /H+/ in the solution and give an indication of the rates and extensiveness of glycolysis in the tissue and its effect on the post-mortem tenderization (DeFremersy and Pool 1988)
MATERIAL AND METHODS
200broiler chicks (120 males and 80 females) of hybrid combination ROSS 208 were used in this experiment.
Chicks were fattened separately according to their sex in pens on deep litter from 1 day old to 16 weeks of age (males) and 9 weeks of age (females) on a starter  22% protein ,3100 Kcal ME and 20% p ,3200Kcal ME as finisher. to the end of the experiment.
At the end of the 5th  week and in every following week till the end of the experiment samples of 10 males and 10 females were slaughtered ,eviscerated and measured the pH values of meat immediately  after slaughtering and then after24 hours by means of meat liquid extraction method by using a laboratory instrument with 2 electrodes.
Results and Discussion

Changes in the pH values in the breast muscles of broiler chicks;
The pH values were measured at the age of 56-63 days for females and 56-1212 days for males.
The dynamics of pH values in breast muscles after 2 and 24 hours of slaughtering are shown in table (1)
Table (1): Dynamics and t-test of pH 2 and pH 24 values of breast in relation to sex and age
Effect of Sex, Age and Live Weight on the PH Values of Breast Meat in Broiler Chickens - Image 1
1) Mean +/- standard error of the mean            P++   0.01
With male chicks ,the pH value after 2 hours of slaughtering increased from 6.04 (56days) and reached its maximum of 6.33 at 112 days of age ,while pH values 24 hours after slaughtering decreased from 5.97 (56 days) and reached the minimum of 5.82 at 112 days.
On the contrary, with females, the pH 2 moderately decreased from 6.02(56 days), while pH 24 in the same direction increased from 5.66 (56 days) to 6.01 at 63 days of age.
In table (1) significant differences were observed in pH24 values at 56 days ,and the breast muscles of male chicks showed significantly higher (P  0.01 ))pH24 values (5.97) than females (5.66) .At 63 days of age no significant difference was observed in pH2 and pH24 values and in pH2 value at 56 days of age between both sexes. Here we can see that at 56 and 63 days of age the pH24 value lower still (5.0-6.0) what indicate that the breast muscles are normal.
The course of post-mortem biochemical changes was normal; the energy was reserved in the muscles and gradually degraded. This shows the great ability of muscles to bind water.
Changes in pH values 2 and 24 hours after slaughtering were discussed by Ingr (1986) and Dodge (1980).
The dependence of the pH values 2 and 24 hours after slaughtering (Y) on the age and live weight of chicks was expressed by linear and parabolic regression equations as shown in table (2)
Table (2) Dependence of pH2 and pH24 of breast muscles of male and female chicks on age and live weight on the chicks-regression equations:
Effect of Sex, Age and Live Weight on the PH Values of Breast Meat in Broiler Chickens - Image 2
1) The significance of regression coefficient b.  P+   0.05     P++   0.01
2) Parabolic regression is better than linear regression P+  0.05 P++   0.01
The age significantly (P 0.01) affected the pH2 and pH24 values of the breast muscles of males and pH24 values of the females..
As age advanced, the pH2 values of males and poH24 of females increased daily by 0.0053 and 0.06971, while the pH 24 of the breast muscles of males decreased by 0.00369..The dependence of these values was expressed by linear regression ,but dependence of pH2 and pH24 values of males and pH values of the females on age was better expressed by parabolic equations with a correlation index of 0.597,0.386 and 0.768 ,In the same direction ,the above pH values were significantly (P  0.01) affected by the live weight of the chicks in grams. As the live weight of chicks increased by 1 gram, the pH2 values of breast of males and pH 24 value of females increased by 0.00007 and 0.00081 ,while the pH24 values of males decreased by 0.00005.Moreover ,this dependence was exactly (P  0.01) expressed by parabolic equation than linear regression.
Conclusion
The pH2 values of males increased from 6.04 (56 days) to 6.33 (112 days).
For females pH2 decreased from 6.02(56 days) to 5.99 (63 days) .
At 56 days significant differences were observed in pH24 between males (5.97) and females (5.66).
The age significantly (P  0.01) affected the pH2 and pH24 values of breast muscles of males and pH24 values of females.
As live weight of chicks increased by 1 gram pH2 values of breast of males and pH24 values of females increased by 0.00007 and 0.00081 ,while pH24 of males decreased by 0.00005.  
References
1-DODGE, J.W-PETERS, F.E.: Temperature and pH changes in poultry breast muscle at slaughter, Poult.Sci.63765-768 1960
2-NADERA, D.N.: Biochemistry of avian meat, hydration.I .comparison of various species, Poult.Sci.49:1935, 1970
3-NADERA, D.N:-MacDonald, B.: Biochemistry of avian meat hydration 2-Factors affecting the hydration of broiler meat.Poult.Sci.49:1446, 1970
4-UHRIN, V.-HORVATOVA,N-LAGIN,L._KOCIVA,E.:Akostne  ukazovatele vykrmovej hydiny a jej nutricna hodnota.Zbor.zo seminara Intenzifikacne factory vyroby hydinoveho masa,1985,pp.105-120
5-SEEMANN, G.: Anmerkungzurverlangerten Broiler mast Dtsch.Geflugewirt .38 945-946, 1986.
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Authors:
Drmostafa Elsabbagh
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