Submitted to: National Egg Quality School Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/30/2010
Publication Date: 5/17/2010
Citation: Jones, D.R. 2010. Understanding and Measuring the Haugh Unit. National Egg Quality School Proceedings. IV:43-44.
Technical Abstract: Rapidly determining shell egg quality in an objective manner is not an easy task. Candling is most often utilized as a quick method for assessing egg quality in a non-destructive manner, but it is a highly subjective method. As you have experienced this week, it is almost impossible for multiple people to grade an egg exactly the same when candling. Ultimately, perceived physical egg quality is an interaction of the thick albumen and yolk stability (centering of the yolk in the thick albumen). Raymond Haugh developed the Haugh unit in 1937. It has become the most widely used measurement of albumen or interior egg quality and by many is considered to be the “gold standard” of interior egg quality determination. The Haugh unit is a correlation between egg weight and the height of the thick albumen. The calculation (which can be cumbersome) is weighted for a 56.7g (2 oz) egg (large size). Several authors have argued that the calculation is inaccurate for eggs other than size large. (Please contact me if you would like copies of these articles.) Haugh unit measurement is a destructive test and is generally conducted on a grading sample of eggs within a lot. The USDA Agriculture Marketing Service (AMS) has accepted the Haugh unit as a valid and reliable method for determining interior egg quality. USDA grade standards have been established for Haugh unit readings (Table 1) and may be found in AMS 56.210 (http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELDEV3004376). These grade/score combinations are not the same for all countries. Therefore, if you export product, you need to investigate requirements for individual countries.