Hops was a well-known agricultural product in Europe by the 9th century. Records from two French abbeys, St. Germain-des-Pres and St. Remi, both show sizable quantities of hops brought in from a number of estates. In this case, it was largely used for medicinal purposes, having a mild analgesic effect as well as being purported to induce sleep.
The first documented link between hops and brewing comes from Picardy in Northern France, in 822, where Abbot Adalhard of the Benedictine monastery of Corbie, in the Somme valley near Amiens, wrote a series of statutes on how the abbey should be run. The many rules covered areas such as the duties of the abbey’s tenants, which included gathering of firewood and also of hops – implying wild hops, rather than cultivated ones. Adalhard also said that a tithe (or tenth) of all the malt that came in should be given to the porter of the monastery, and the same with the hops. If this did not supply enough hops, the porter should take steps to get more from elsewhere to make sufficient beer for himself.
A German abbess named Hildegaard living in the abbey of Rupertsberg near the town of Bingen-am-Rhein documented hops use in beer in Physica Sacra, published c.1158. Her treatise is the first indication we have of hops being used for its preservative qualities rather than simply for flavoring.
It is warm and dry, and has a moderate moisture, and is not very useful in benefiting man, because it makes melancholy grow in man and makes the soul of man sad, and weighs down his inner organs. But yet as a result of its own bitterness it keeps some putrefactions from drinks, to which it may be added, so that they may last so much longer.
A very detailed explanation of the best time to plant hops and the best methods for ensuring a good crop are described in Mascall’s treatise on planting and grafting of agricultural products. Mascall goes on to explain how to prepare the hops for use in the brewery.
When your Hoppes be well tossed and turned on boorded floores, and well dryed (as I haue afore shewed) ye shall put them into great sackes according to the quantitie of your Hoppes, and let them be troden downe hard togither, which will kéepe their strength longer, and so yée may reserve them, and take at your pleasure. Some doe use, (which have but small store) to treade them into drie fattes, and so reserve them for their use, which is counted the better way and the lesse portion doth serve, and will longer kéepe their vertue and strength.
Hops contain two types of acid – alpha and beta. The alpha acids contain the chemical agents Humulone, Cohumulone and Adhumulone used to impart bitterness. Alpha resins are not very soluble and must be boiled to impart bitterness in the beer. Beta acids are used to impart flavor and aroma. Unlike the alpha acids, these oils are water soluble and will quickly boil off. Typically, hops will impart flavor if boiled between 5-15 minutes and aroma if boiled for 1-3 minutes.
 Unger, pg. 54
 Von Bingen, Book I, Chapter 61
 Mascall, pg. 86
 Ibid, pg. 89
Cornell, Martyn (2009). “A Short History of Hops”, Zythophile: Beer Now and Then. Retrieved 11 February 2015, from https://zythophile.wordpress.com/2009/11/20/a-short-history-of-hops.
“Hops”. British Brewer. Retrieved 11 January 2017, from http://www.britishbrewer.com/2010/02/hops.
Mascall, Leonard (1589). Booke of the art and maner, how to plante and graffe all sorts of trees Arte of planting and graffing. London: Henrie Denham.
Unger, Richard W. (2007). Beer in the Middle Ages and the Renaissance. University of Philadelphia: Pennsylvania Press.
von Bingen, Hildegaard (c.1158). Physica. Priscilla Throop (translator). San Francisco: Healing Arts Press, 1998.