Eventually, the temperature of the mash is raised to 75 °C, which effectively inactivates nearly all enzymatic activity. The insoluble material in the mash liquid is then separated by one of several means (discussed below).This is an important step because the mash still contains grain solids and insoluble proteins, carbohydrates, and other materials. In addition, within the mash solids is a reasonable amount of soluble materials,including fermentable sugars, that would otherwise be discarded with the spent grains.

For some breweries, the mash tun can also provide filtration. These tanks contain a false bottom that allows most of the mash liquid to flow out of the tank and into a collection vessel, while at the same time retaining a portion of the mash containing the spent grains. The spent grains form a filter bed that enhances flow rate (depending on the fineness of the malt). This material is then stirred and sparged with hot liquid to extract as much of the soluble material as possible. The liquid is added to that already removed from the mash tun.An alternative process involves pumping the mash into a separate tank called a lauter tun, which also contains a false bottom and sparging system and operates much like the mash tun, except it provides greater surface area and faster and more efficient filtration. Because the initial liquid material obtained from the lauter tun (or the mash tun) often still contains solids, it may be recycled back until a better filter bed is established and the expected clarity is achieved.

Finally, the mash separation step can be performed using plate and frame type filtration systems. These systems consist of a series of connected vertical plates, housing filters of various composition and porosities.The mash liquid is pumped horizontally through the sys-tem.As for the mash and lauter tuns, the filtrate can be recycled and the entrapped material can be sparged to enhance extraction.

The liquid material or filtrate that is collected at the end of the mash separation step is called "wort." Since it is the wort that will be the growth medium for the yeast, and which will ultimately become beer, its composition is very important (Table 9-3).The main component of wort (other than water) is the carbohydrate fraction (90%). Most (75%) of the carbohydrates are in the form of small, fermentable sugars, including maltose, glucose, fructose, sucrose, and maltotriose.The rest, about 25% of the total carbohydrate fraction, are longer, nonfermentable oligosaccharides that include dextrins (a-1-4

Box 9—3. The Reinheitsgebot

Among the most ancient of all laws related to foods is the German Purity Law known as Reinheitsgebot. These brewing laws were established in 1516 by Bavarian dukes Wilhelm IV and Ludwig X in response to the frequent occurrences of what we would now call adulteration. During this time, brewers had begun to add questionable, if not dangerous, substances to beer in an effort to disguise defects and deceive consumers as to the quality. Brewers had been known to add tree bark, various grains, herbs, and spices to make the beer more palatable.These unscrupulous beer traders were giving the legitimate brewers of Bavaria a rather bad name. Thus, these laws were written to protect the brewing industry and perhaps to protect consumers. It is interesting to note that the ingredients clause (in bold) is but a part of the Reinheitsgebot—most of the law deals with the price that brewers can charge for beer.

Below is an English translation of the Reinheitsgebot, taken from the article "History of German Brewing" by Karl J. Eden, published in Zymurgy,Vol. 16, No. 4 Special 1993.

"We hereby proclaim and decree, by Authority of our Province, that henceforth in the Duchy of Bavaria, in the country as well as in the cities and marketplaces, the following rules apply to the sale of beer: From Michaelmas to Georgi, the price for one Mass1 or one Kopf2, is not to exceed one Pfennig Munich value, and From Georgi to Michaelmas, the Mass shall not be sold for more than two Pfennig3 of the same value, the Kopf not more than three Heller4.If this not be adhered to, the punishment stated below shall be administered.

Should any person brew, or otherwise have, other beer than March beer, it is not to be sold any higher than one Pfennig per Mass. Furthermore, we wish to emphasize that in future in all cities, markets and in the country, the only ingredients used for the brewing of beer must be Barley, Hops and Water. Whosoever knowingly disregards or transgresses upon this ordinance, shall be punished by the Court authorities' confiscating such barrels of beer, without fail. Should, however, an innkeeper in the country, city or markets buy two or three pails of beer (containing 60 Mass) and sell it again to the common peasantry, he alone shall be permitted to charge one Heller more for the Mass of the Kopf, than mentioned above. Furthermore, should there arise a scarcity and subsequent price increase of the barley (also considering that the times of harvest differ, due to location),We,the Bavarian Duchy, shall have the right to order curtailments for the good of all concerned."

Note that, in contrast to the often-quoted statement that only four ingredients are permitted, the Reinheitsgebot actually restricts beer making to just three ingredients: barley, hops, and water. This is because the fourth ingredient, the yeast, had not yet been "discovered." Rather, early brewers either relied on a natural fermentation (i.e.,with wild yeast initiating the fermentation) or else used a portion of a previous batch to start the fermentation (i.e., backslopping).

The Reinheitsgebot is still in effect today in Germany, although it has been re-written and is now more explicit.The current laws also have been modernized, such that hop extracts and filter aids are now permitted. In addition, there is now a distinction made between lagers and ales, with exceptions regarding adjuncts and coloring agents allowed for the latter.


1. One Mass=one mug, or about a liter

2. Kopf is a bowl-shaped container for fluids, not quite one Mass

3.Two Pfennig=two pennies

4. One Heller=one-half Pfennig linked glucose molecules) and limit dextrins (a-1,4 and a-1,6 glucose molecules). A small amount of p-glucans (p-1,4 and p-1,6 linked glucose molecules), derived from the cell walls of the barley, may also be present.

In addition to the carbohydrate fraction, wort also contains 3% to 6% nitrogenous matter, including proteins, peptides, and free amino acids. Proportionally less protein, relative to the total solids, will be present if adjuncts are used.About half of the amino acids will eventually be used to support yeast growth, and the other half remaining in the wort contributes to flavor and browning reac-tions.Various ions (e.g., ionic calcium, magnesium, and carbonates) are also present.The final pH of the wort is around 5.2.

The average molecular weight of the protein fraction is very important, because it determines the "palate fullness" or mouth feel, and also affects the physical stability (cloudiness), color, and the foamability. In general, the greater the protein hydrolysis, the less cloudy the beer. However, foam stability also is reduced. In contrast, the less hydrolyzed the protein, the more likely there will be cloudiness problems.

Table 9.3. Approximate composition of mash, wort, and beer (g/100 ml)1,2.






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