The Haugh unit is a measure of egg protein quality based on the height of its egg white (albumen). The test was introduced by Raymond Haugh in 1937 and is an important industry measure of egg quality next to other measures such as shell thickness and strength.


            On storage the integrity of albumin structure is lost; as a result albumin spreads thinly when broken on a cooking surface. Egg weight, albumen and yolk height, Haugh unit, albumen and yolk indices decreased with increase in storage time while albumen and yolk width increased. Egg length and width were not affected by storage time and method. The quality of egg albumin is measured by measuring Albumin index, Haugh’s unit


            H.U varies with storage – 82 at farm; 77 for whole sale; 60 for retail. For an egg of poor quality H.U ranges from 36-60 while for a egg of good quality HU is 72.





Instrument required


  1. Tripod micrometer

  2. weighing balance






Procedure





  1. Take a sample (egg)

  2. egg is weighed

  3. after that egg is broken onto a flat surface (breakout method), and a micrometer used to determine the height of the thick albumen (egg white) that immediately surrounds the yolk.

  4. The height, correlated with the weight, determines the Haugh unit, or HU, rating.






The higher the number, the better the quality of the egg (fresher, higher quality eggs have thicker whites). Although the measurement determines the protein content and freshness of the egg, it does not measure other important nutrient contents such as the micronutrient or vitamins present in the egg.



Formula




The formula for calculating the Haugh unit is:


HU = 100 * log(h-1.7w^{0.37} + 7.6)


Where:


·        HU = Haugh unit


·        h = observed height of the albumen in millimeters


·        w = weight of egg in grams





  • H.U is the function of height of thick albumin and weight of the egg. Measurement of height of thick albumin is done by using micrometer.


















Haugh Unit rating

Quality of eggs

90 and above

Excellent

80 - 89

Very good

70 - 79

Acceptable

65 - 69

Fair

60 - 64

Consumer resistance point*

55 - 59

Poor

50 and below

Unacceptable