Editing Rennet (section)

==Extraction of calf rennet==
[[calf (animal)|Calf]] rennet is extracted from the inner [[mucosa]] of the fourth stomach chamber (the [[abomasum]]) of young, nursing calves as part of livestock butchering. These stomachs are a [[byproduct]] of [[veal]] production.<ref>{{Cite book |title=Traditional Cheesemaking Manual |url=https://books.google.com/books?id=mCBrre1_7I4C&pg=PA6 |page=6 |last=O'Connor. |first=C. |publisher=ILRI|isbn=9789290532736 |date=1993-01-01 }}</ref> Rennet extracted from older calves ([[grass-fed]] or [[Grain-fed beef|grain-fed]]) contains less or no [[chymosin]], but a high level of [[pepsin]] and can only be used for special types of milk and cheeses. As each ruminant produces a special kind of rennet to digest the milk of its own species, milk-specific rennets are available, such as kid goat rennet for [[goat's milk]] and lamb rennet for [[sheep's milk]].<ref>{{cite web |last1=Singley |first1=Nora |title=What You Might Not Know: Not All Cheeses Are Vegetarian! |url=https://www.thekitchn.com/a-complete-meal-vegetarian-the-112672 |website=Kitchn |publisher=Kitchn.com |access-date=30 January 2022}}</ref>

=== Traditional method ===
Dried and cleaned stomachs of young calves are sliced into small pieces and then put into salt water or [[whey]], together with some [[vinegar]] or [[wine]] to lower the [[pH]] of the solution. After some time (overnight or several days), the solution is filtered. The crude rennet that remains in the filtered solution can then be used to coagulate milk.  About 1 gram of this solution can normally coagulate 2 to 4 litres of milk.<ref>{{Cite book|url=https://books.google.com/books?id=lM-mtPn9WwoC|title=Brined Cheeses|last=Tamime|first=Adnan Y.|date=2008-04-15|publisher=John Wiley & Sons|isbn=978-1-4051-7164-9|language=en}}</ref>

=== Modern method ===
Deep-frozen stomachs are milled and put into an enzyme-extracting solution. The crude rennet extract is then activated by adding acid; the enzymes in the stomach are produced in an [[Zymogen|inactive form]] and are activated by the [[stomach acid]]. The acid is then [[Neutralization (chemistry)|neutralized]] and the rennet extract is filtered in several stages and concentrated until reaching a typical potency of about 1:15,000; meaning 1&nbsp;g of extract can coagulate 15&nbsp;kg of milk.{{Citation needed|date=July 2019}}

One kilogram of rennet extract has about 0.7&nbsp;g of active enzymes – the rest is water and salt and sometimes [[sodium benzoate]] ([[E211]]),
0.5%–1.0% for preservation. Typically, 1&nbsp;kg of cheese contains about 0.0003 g of rennet enzymes.<ref>{{Cite web|title=Cheese Technology: Lesson 14. CALF RENNET: PREPARATION AND PROPERTIES|url=http://ecoursesonline.iasri.res.in/mod/page/view.php?id=147314|access-date=2021-02-04|website=ecoursesonline.iasri.res.in}}</ref><ref>{{Cite web|date=2017-08-31|title=Hooked on Cheese: Cheese for Vegetarians|url=https://www.thedailymeal.com/eat/hooked-cheese-cheese-vegetarians|access-date=2021-02-04|website=The Daily Meal|language=en}}</ref>