Lecture 15 Beverage Fermentation. Ales & Lagers. History. Chemical analysis of 7,000 year-old jugs puts invention of beer around the same time period as wine
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Ales & Lagers
Chemical analysis of 7,000 year-old jugs puts invention of beer around the same time period as wine
Addition of hops to beer occurred about one thousand years ago but before the 14th century spruce, ginger, wormwood, sage, and sweet mary were more popular.
1516 Bavarian purity law passed, oldest known food purity law still in effect, limited ingredients of beer to hops, barley, and water.
16th century lager beer type accidentally invented during cold cave fermentation.
Beers in America were largely heavy beers, until prohibition ended most American breweries.
Now the beer market is nearly monopolized by Anheuser-Busch, who made a fortune producing cheaper, watery, light beer for women workers during World War II. The American pallet now reflects this with preference for lighter beer.
Yeast can be found naturally on the surface of most plants including barley seeds.
“Wild” yeast will most likely produce flavors that are undesirable.
During the fermentation process, undesirable microbes must be kept out of the beer.
Saccharomyces cervisiaeis the species most often used for ales, its optimum fermentation temperature is 16-24 C
Saccharomyces uvarium is largely used in lagers, and steam beers. The optimum temperature for this fermentation is 2-13 C
Over a 15 square mile area near Brussels the resident wild yeast and bacterial populations are perfect for spontaneously fermenting, beer. This fruity sour beer is known as a “lambic”.
Major Reaction: Glucose to Carbon Dioxide and Ethanol
Special flavors and aromas of beers arise from minor biochemical reactions
These flowers not only fight off bacterial infections in the beer, they aid in clarification of the beer, stabilize the flavor, help retain head, and aid in ones ability to drink the beer.
Hop oils are produced in the Lupulin glands of the flower.
The oils are made of α and β-acids, but α-acids contributes more to the bittering of a beer.
These oils are non-polar, and can only be extracted through a short boiling.
Malted Barley and
Malted barley and specialty grains are run through roller mill and cracked open.
This grist is then carried by an auger to the mash tun.
In the mash tun the grist is mixed with hot water to form a mash.
In the mash, enzymes that exist in the grain become active and convert the starches to fermentable sugar.
The sugar rich liquid from the mash, called wort, is drained from the mash tun.
The wort is drained from the mash tun and moved to the brew kettle.
In the brew kettle the wort is boiled and hops are added.
From the hops we can extract bitterness, which will help balance the sweetness of the wort.
After boiling, the wort is transferred through a chiller.
While passing through the chiller the wort is instantly chilled to the appropriate temperature for fermentation.
From the chiller, the wort moves into a temperature controlled fermenter.
Yeast is added and fermentation begins. In fermentation the yeast will ferment sugars in the wort and produce alcohol, carbon dioxide, and other flavor compounds.
Intermediate of ethanol production.
It can form in autolysis of yeast during lagering if yeast is in poor condition.
It can also form if post-fermentation beer is exposed to air (oxygen).
Ethanol can be oxidized to acetaldehyde.
Formed from a secondary reaction of alcoholic fermentation.
Pyruvate decarboxylase converts pyruvate to acetaldehyde, which is then converted to ethanol and CO2.
Pyruvate decarboxylase sometimes joins two acetaldehyde molecules to form acetoin.
After fermentation the fermented wort, now called beer, is transferred through a filter.
The filter removes various proteins, hop residue and yeast cells.
From the filter, the beer moves to the beer servers.
These are carbonating tanks, holding tanks and serving tanks.