Editing Lactose (section)

==Occurrence and isolation==
Lactose comprises about 2–8% of milk by weight. Several million tons are produced annually as a by-product of the [[dairy industry]].{{cn|date=May 2024}}

[[Whey]] or milk plasma is the liquid remaining after milk is curdled and strained, for example in the production of [[cheese]]. Whey is made up of 6.5% solids, of which 4.8% is lactose, which is purified by crystallisation.<ref>{{Citation |last1=Ranken |first1=M. D. |title=Food industries manual |url=https://archive.org/details/foodindustriesma0000unse |page=125 |year=1997 |publisher=Springer |isbn=978-0-7514-0404-3 |last2=Kill |first2=R. C.}}</ref> Industrially, lactose is produced from whey permeate – whey filtrated for all major [[protein]]s. The protein fraction is used in [[infant nutrition]] and [[sports nutrition]] while the permeate can be evaporated to 60–65% solids and crystallized while cooling.<ref>{{citation |last1=Wong |first1=S. Y. |title=Crystallization in lactose refining-a review |journal=[[Journal of Food Science]] |volume=79 |issue=3 |pages=R257–72 |year=2014 |doi=10.1111/1750-3841.12349 |pmid=24517206 |last2=Hartel |first2=R. W.|doi-access=free }}, DOI is open access</ref> Lactose can also be isolated by dilution of whey with [[ethanol]].<ref>{{citation |title=Introduction to Organic Laboratory Techniques: A Microscale Approach |first1=Donald L. |last1=Pavia |first2=Gary M. |last2=Lampman |first3=George S. |last3=Kriz |publisher=Saunders |year=1990 |isbn=0-03-014813-8 }}</ref>