Albumen - albumin

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The two words albumen and albumin are easy to confuse. They are similar in spelling, virtually identical in pronunciation, have very similar meanings (which vary over time), and share an etymology.

They are pronounced in RP with the stress on the first syllable, and an intrusive '-y-' in the second. In GA, the stress is on the second syllable, 'alb-YOU-men', /ælb ˈjuː mə (or ɛ or ɪ)n/. The third vowel is always close to a shwa, but may be distinguished if the two come up in the same context. 'ALB-you-men', IPA: /ˈælb juː mə (or ɛ or ɪ)n/.
  • Albumen is best used these days only to mean what cooks call the 'white' of an egg.
  • Albumin is currently the term for "(as a count noun) a member of a class of simple globular proteins that are soluble in water, moderately soluble in salt solutions, and denatured by heat; (as a mass noun) protein of this form" (OED, 2012).
The original term for this was albumen, and indeed albumen belongs to the class of albumins. So confusion is always possible.
Etymological note: albus is the Latin adjective meaning 'white'. Since the fifth century, albumen has been used for 'the white of an egg'; before that, the word was used to mean 'a disease of the eye'. In the nineteenth century, it became a technical term in photography, where some early prints used egg-white to coat paper before being further coated with photo-sensitive chemicals such as silver nitrate. In this field the verb 'to albumenize' became common.