# Beer > Grain sugars fermented into alcohol - Date: c. 3,500 BCE - Era: Prehistory - Domain: [Food & Preservation](https://lastcodex.org/en/domains/food/) - Rebuild stage: II (Settlement) - Difficulty: 2/5 - URL: https://lastcodex.org/en/inventions/beer/ Beer is made by turning the starch of sprouted grain into sugar and letting yeast ferment that sugar into alcohol. Chemical traces of barley beer go back to the fourth millennium BCE in western Iran, and brewing has followed farming almost everywhere cereals were grown. ![Beer · Grain sugars fermented into alcohol](https://lastcodex.org/_astro/plate.Dpn6F3Co_1vK9XO.webp) ## Legend 1. Malted barley 2. Mash tun 3. Brew kettle 4. Cooler 5. Fermenting vat 6. Casks ## What it is Beer is a fermented drink made from cereal grain, most often barley, with water, yeast and usually hops. Yeast cannot feed on starch, so the grain is first malted and mashed to turn its starch into sugars that yeast can ferment into alcohol and carbon dioxide. The plate shows a small brewhouse of the kind used in Europe before steam power, with the vessels set out in the order of the work: malt, mash tun, kettle, cooler, fermenting vat and casks. ## How it works First the barley is malted: it is soaked and left to sprout for several days. As the seed starts to grow, it produces enzymes that will later break down its own store of starch. The maltster then dries the grain in a kiln to stop growth; the heat also sets the colour and flavour of the malt, from pale to roasted. ![A barley ear beside sprouting grains with white rootlets, one grain cut open to show the shoot under the husk](https://lastcodex.org/_astro/v1.9bdRZ68C_ZHWMKP.webp) _Malting: the sprouting grain makes the enzymes that brewing needs, and the kiln stops it before it uses up its starch._ In the mash, the malt is crushed and steeped in hot water. Between about 62 and 68 °C the malt's amylases cut the starch into sugars, mainly maltose, in an hour or so. A cooler mash leaves more fermentable sugar and a drier beer; a hotter one leaves more unfermentable sugar and a fuller body. The sweet liquid, the wort, is drained off through the husks, which act as a filter. The wort is then boiled for an hour or more. Boiling kills most of the microbes that came in with the grain, stops the enzymes and drives off unwanted aromas. Hops added at this stage give bitter compounds that also slow the growth of many spoilage bacteria; hops added near the end keep more of their scent. Finally the wort is cooled and yeast is added. Over several days the yeast turns the sugar into ethanol and carbon dioxide, along with the esters and other compounds that shape the taste. Ale yeast works warm and rises to the top; lager yeast works cool and settles to the bottom. A period of storage then lets the beer clear and mature. ## How to build it A small batch of about 10 litres can be brewed in a kitchen with the brew-in-a-bag method. You need 2.5 kg of crushed pale malt, about 25 g of hops, a packet of ale yeast, a 20-litre pot, a large mesh bag, a thermometer, a fermenter with an airlock, a hydrometer, a no-rinse sanitiser, and bottles with new caps. **Mash.** Heat 14 litres of water to about 70 °C, put the bag in the pot and stir in the malt. The mash should settle near 66 °C. Turn off the heat, then cover the pot and wrap it in a blanket for an hour, keeping the blanket well clear of the burner. Take the blanket off, lift out the bag and let it drain. **Boil.** Bring the wort to a rolling boil for 60 minutes. Add most of the hops at the start for bitterness and the rest in the last ten minutes for aroma. Watch the pot as it comes to the boil, because the foam rises fast. Meanwhile clean and sanitise the fermenter and everything else that will touch the cooled wort; a clean immersion chiller can be sanitised by standing it in the boiling wort for the last 15 minutes. **Cool and ferment.** Cool the covered pot to about 20 °C with the chiller or in a sink of cold water. Pour the wort into the fermenter, add the yeast, fit the airlock and keep it at 18 to 20 °C. **Bottle.** Fermentation usually takes one to two weeks. Bottle only when the hydrometer gives the same reading on three days running and that reading is close to the expected final gravity, about 1.010 to 1.015 for this recipe: a higher steady reading means a stuck fermentation, not a finished one. Dissolve 5 to 6 g of sugar per litre in a little boiled water, mix it gently into the beer, fill and cap the bottles, and keep them at room temperature for two weeks before chilling. > **Safety.** A pot of boiling wort can cause severe scalds: keep it on a stable burner, lift it with a second person or not at all, and keep children and pets away. Indoors, use only a hob or cooker made for indoor use; burners sold for outdoor use stay outdoors. Too much priming sugar, or bottling before fermentation has finished, can make bottles burst; use real beer bottles, weigh the sugar, and wear eye protection when handling a batch that seems over-carbonated. Never try to distil the beer. Follow the local law on home brewing and on alcohol. ## History and evolution ![A large clay jar of Mesopotamian beer with two long reed straws reaching down through the floating husks](https://lastcodex.org/_astro/v2.CVJqb0hQ_Z1iRCKQ.webp) _In Mesopotamia, drinkers shared a jar and sucked the beer through long straws that reached below the floating husks._ Residues in stone mortars at Raqefet Cave in Israel, about 13,000 years old, have been read as traces of a gruel-like brew made by Natufian foragers for funeral feasts; the interpretation is debated. An early and widely cited chemical trace comes from Godin Tepe in western Iran, where grooves inside a jug of the late fourth millennium BCE hold calcium oxalate, the "beerstone" that barley beer deposits in brewing vessels. Calcium oxalate is not unique to beer, so this reading has been questioned too. Mesopotamian tablets mention beer thousands of times, yet give no recipe. The closest is the Hymn to Ninkasi, the goddess of brewing, written down around 1800 BCE, which describes soaking malt, spreading the mash on reed mats and filling the vats. In Egypt beer was a staple food, and a large brewery from about 3000 BCE has been excavated at Abydos. ![A hop bine twining up a pole, with three green cones and one cone cut open to show the yellow lupulin](https://lastcodex.org/_astro/v3.DkHbsQcC_8NyoA.webp) _The yellow lupulin glands inside the hop cone hold the bitter resins and the aroma._ Medieval European brewers flavoured beer with gruit, a mix of herbs. Abbot Adalhard of Corbie mentioned hops for beer in 822, and hopped beer, which kept better, spread slowly over the following centuries. On 23 April 1516 the dukes of Bavaria ruled at Ingolstadt that beer could contain only barley, hops and water. Yeast was not on the list, because its part in fermentation was not yet understood; Louis Pasteur showed in the 1850s that fermentation was the work of living cells. At the Carlsberg laboratory in Copenhagen, Emil Christian Hansen found that wild yeasts mixed into the brewers' yeast caused "beer sickness". He grew a pure culture from a single good yeast cell, first used for a full-scale brew in November 1883, and lager became far more reliable. Carlsberg gave the yeast to other brewers. ## Key figures - Early chemical trace of barley beer (debated): Godin Tepe, Iran, late 4th millennium BCE - Usual mash temperature: About 62 to 68 °C, where the malt's starch-splitting enzymes work best - Bavarian purity law: 23 April 1516, Ingolstadt: barley, hops and water only - First pure-culture yeast in production: Carlsberg, Copenhagen, November 1883 ## Requires - [Pottery](https://lastcodex.org/en/inventions/pottery/): Clay turned to stone by fire (18,000 years ago) - [Bread](https://lastcodex.org/en/inventions/bread/): Ground grain, water and heat (12,400 years ago) ## Sources - [Five things I learned about Sumerian beer](https://mag.uchicago.edu/arts-humanities/five-things-i-learned-about-sumerian-beer), University of Chicago Magazine - [Purifying yeast](https://www.carlsberggroup.com/pursuit-of-better/scientific-discoveries/purifying-yeast/), Carlsberg Group - [500 Jahre Reinheitsgebot: Deutsches Bier, was darf rein und was ist drin](https://www.test.de/500-Jahre-Reinheitsgebot-Deutsches-Bier-was-darf-rein-und-was-ist-drin-4991639-0/), Stiftung Warentest - [The brewing process](https://blogs.cornell.edu/brewing/?p=116), Cornell Brewing Program, Cornell University - [History of beer](https://en.wikipedia.org/wiki/History_of_beer), Wikipedia - [Mashing](https://en.wikipedia.org/wiki/Mashing), Wikipedia Fact-checked on 2026-10-12. --- The Last Codex · https://lastcodex.org/en/inventions/beer/ · © The Last Codex. Texts, plates and figures: CC BY-NC-ND 4.0.