Meat Science

CHEMICAL METHODS 

• The chemical tests consist of the determination of 
  • the content of glycogen in flesh 
  • the percentage of linoleic acid in fat 
  • the melting point of fat
  • the amount of iodine absorbed by unsaturated fatty acids in fat and 
  • the refractive index of fat.                                                                

Test for Glycogen Content of Meat

• The horseflesh is richer than the flesh of other food animals in glycogen in horsemeat as compared with other kinds of meat, glycogen is found in large quantities irrespective of age.
  • Horse – 0.5 to 1.0 % 
  • Beef - 0.0 to 0.5% 
  • Pork and mutton - nil
• Disadvantages
  • The flesh should be tested for the content of glycogen soon after the slaughter as it disappears from the flesh quickly.
  • Liver of all food animals especially pig liver contains more glycogen when they are used in sausage making it gives a high percentage. So care must be taken in interpretation of results.

Linoleic acid content

• Horse fat contains 1-2% linoleic acid.  Linoleic acid content in other animals' fat is not more than 0.1%. 
• Thus adulteration of lard or beef and mutton fat with horse fat can be identified by estimation of the linoleic acid concentration.

Iodine value

• Estimation of iodine value is a valuable test for the detection of horse fat.          
• Iodine value is the amount of iodine absorbed by the unsaturated fatty acid present in the fat.
• Good lard has an iodine value of 66. 
• The iodine value of the fat from various food animals is:
  • Horse  - 71-86
  • Ox (cattle) - 38-46
  • Sheep  - 35-46
  • Pig  - 50-70

Refractive index

• Refractive index is another valuable test for the detection of fat of different animal species. 
• Fat is liquefied by heat and converted into oil for estimation of refractive index.     
• All liquids including oils possess a specific refractive index.
  • Horse - 53.5
  • Ox - less than 40
  • Pig - not above 51.9

Melting Point

• The melting point of fat varies with the species of food animals and the kind of feed fed to the animal. 
• The range of melting points of fat is

Myoglobin content

• The myoglobin content of different species is:
  • Beef - 0.30 to 1%
  • Pork - 0.06 to 0.40%
  • Poultry - 0.02 to 0.18%

Other chemical tests for differentiation of different meat species are:

• Estimation of muscle nitrogen fraction
• Myoglobin content
• Muscle enzymes
• Composition of fat
• Carotene content
• Fatty acid composition