BREWING WILL H. SHEARON, JR. .Associate Editor
in cnllahoration with
HAROLD E. WEISSLER Son .Antonio Brewing Association Sun Antonio, Ter.
Filling Beer Kegs fmm Racker a t Pearl Brewery of San Antonio Brewing Association
A Staff-IndustryCollaborative Report.
T
H E origin of beer is one of the lost pages of history. The Chinese, great invent018 of an earlier age, are said to have discovered it. The ancient Babylonians, Egyptians, and the Hebrews of the Old Testament had their beer, as did the Greeks and the Romans,each under its own name. We shall never know which low-browed prehistoric man was the first to quench his thirst with a draft of beer brewed in the darkness of mme longforgotten cave. But of this we are certain-the making of beer ws8 one of the h t practical experiments ever attempted by man in the field of biochemistry (26). Whatever its origin, the manufacture of beer has long been conaideredananart(i,If,f7). Notuntilthemiddleoftbelastcentury did the e 6 e d of chemistry as a science begin to make itself felt in brewing, but one brewing expert has been quoted as saying that there is no department of the arts and manufactures where chemistry has exerted a more decided influence than in brewing. In his boak on the science of brewing, Hind (6) strikes a wmpromise between the brewmaster and the chemist when be says that brewing is an art, not a science, but no artist is content to work in the dark to rules laid down by his predecessors. His statement in the introduction to the book is worth repeating: More than ever I have been impressed during preparation of
this book by the wide additions to pure scientific knowledge that have originated in the endeavor to elucidate the mysteries of brewing and perhaps equally, by realization of the inadequacy of
our present interpretation of many of them. Until the middle of the last century American beers were of the top-f-ented English type. Because of difficulties in malting and brewing during hot weather due to inadequate refrigeration, manufacturers were quick to adopt German bottom-fermented lager beer introduced in the 1830's. This type beer is completely fermented and undergoes little secondary fermentation on starage; hence it could be stored in cool cellars for hot weather wn-
sumption. In the last 100 years the revolutioniziig of the brewing industry has been clwely associated with the development of artificial IS frigeration and air conditioning for controlled t e m p a t u r e a and
..
psateurieation to ensme biological stability. Today the place of the chemical laboratory in the breweries of this country is established. FUNDAMENTAL OPERATIONS
Beer manufacture consists essentially in preparing ferniwted beverages of a number of types, using barley malt, adjuncts, hops, and water, and fermenting with a bottom fermenting yeast. A typical list of material required for the production of one barrel (a 31.0 gallon barrel is mculiar to the brewina industry) of beelic carbon dioxide evolved. Pressure is allowed to build up t o 4 or 5 pounds per square inch gage, and the evolving gas is cxhausted from the tanks until its purit,y reaches 99.95% carboil dioxide as determined by laboratory analysis. I t is then coll pressed a t 275 pounds per square inch, and stored of supply for later carbonating steps. Safety valvcs are provided on all tanks to prevent excessive pressurer. Carbon dioxide can be collected economically for 3 to 4,days, Fermentation is a metabolic process and may be expi simply by the statement: Yeast
+ carbohydrate + protein -+ethyl alcohol -kcarl)on dioxide + heat
hIichaelis (8)and Siebel (la)some years ago discussed in tlctail in a brewing symposium t,hevarious oxidation problems involvcd infermentation. Temperature of the fermenting beer is never allowed to exceed 57' F., in order to obtain consistent fermentations. If this is not done, attenuation cannot be carefully controlled, byproducts having an adverse effect on flavor and aroma arc formed, and the finished beer is susceptible t o infection and high attenuntion. Hence all fermenting vessels are equipped with copper cooling coils or attemperators refrigerated with brine a t 25 30' F., and the fermenting cellars themselves are rei'rigcr (45' F.). Recording thermometers are used throughout the plant. I n one of the newest British plants ( 4 ) a stainless steel trunnioned attemperator has been installed. One of its main advantages is that it can be swung around, enabling ea.sy cleaning both of the attemperator and the fermenting vessel. After 3 or 4 days in the closed fermenting tanks a portion of thc beer is transferred to 380-barrel yeast collecting tanks, where it is rapidly chilled to the range 36" to 39' F. During this time the yeast flocculates and settles to the bottom of the tank. Any foam that forms on the surface of the beer is skimmed off, since this foam contains bitter hop residues and weak and dead yeast cells. After the yeast has settled (5 to 6 days) the beer is decanted. The yeast, v-hich remains as a mat about 4 inches thick on the bottom of the tank, is stirred carefully and skimmed with a wooden creel to remove residual beer and a very thin layer of yeast. The yeast is then mixed thoroughly without whipping and pulled out into stainless steel buckets. The appa.rent solids content is determined by the laboratory, and the operator is then advised of the proper number of pounds of yeast t o pit,rh.
June 1951
INDUSTRIAL AND ENGINEEEING CHEMISTRY
The progress of fermentation is followed closely by temperature and attenuation checks. Table I1 shows p H and attenuation changes throughout the steps in beer manufacture.
TABLE11. ATTENUATION AND p H CHANGESDURING BEER MANUFACTURE
Water Mash First wort Wort tailings Cooling stage Fermentation, hours 24 72 96
.
144
Rest (in ruh cellars)
PH 6.6
5.6 5.5 5.6 5.6 5.2
4.6
...
...
4.4
Apparent Degree of Attenuation, %
... (180'Piato)
(1' Plato)
...
13.0 42.8 61.0 71.3 83.0
Temperatures are read twice daily by the brewmaster or his assistant and recorded directly on the tank by the laboratory after the fourth day. When the required degree of attenuation is attained, the brine flow through the cooling coils is increased a t a rate calculated to lower the temperature of the beer 0.45 F. per hour a t the beginning; the rate of cooling is reduced as the temperature is dropped to a final 36" to 39' F. The beer is then passed through coolers ( 4 E ) where it is brought to a temperature of 32" to 34" F.; it is then ready for finishing. The beer from the yeast collecting tank is treated in a similar manner. Finishing
, ,
*
The completely fermented beer is blended for attenuation characteristics and alcohol content and is transferred to 300barrel vertical cylindrical glass-lined tanks (SE, 14E) in rooms known as "Ruh" cellars or rest cellars. I n the transfer from the fermenting to the ruh cellars, the beer is carbonated slightly through a carbonating arm (19E)which injects carbon dioxide directly into the beer as it passes through the pump. The ruh cellars are each complete units in themselves, closed and with individual refrigerating units which maintain them a t 32" F. (freezing point of beer is approximately 28' F.). All tanks in the brewery have individual gages and those in the ruh and finishing cellars are equipped with manometer-type gages. I n the ruh cellars yeast and other material settle out, and certain taste characteristics are developed. This is attributed to ester formation, indirectly confirmed by the fact that during the ruh stage there is a slight but nonetheless uniform decrease in the alcohol content of the beer. Following storage in the ruh cellars, the beer is pumped into the finishing cellars. (Some brewers prefer to carbonate at this point in saturators or tanks, where beer flowing downward is contacted by a stream of carbon dioxide, rather than by partially carbonating a t each pumping step and completing the process in the finishing tanks.) During this pumping operation the beer is clarified by filtering through pressure filters (dOE), capacity 110 barrels per hour each. The plates of the filters have nylon screens and are precoated with diatomaceous earth. Cedar chips were used for clarifying prior t o the introduction of pressure filtration and are still in use by one large brewer. Isinglas is also used as an aid to filtration by some brewers. AddiBional carbonation is carried out a t the pump, temperature is maintained a t 32' F. during transfer, and a proteolytic enzyme is slurried into the beer as it is pumped into the finishing tanks. Typical enzymatic material of this kind may include either pepsin and a bacterial enzymatic material or a proteolytic enzyme of animal or plant origin combined with a metabolic material (enzymes) produced by the cultivation of molds (18). A number of enzymatic compositions are available from different manufacturers. The particular type used at Pearl (17'E) contains a mixture of a number of enzymes including a purified and
1269
standardized proteolytic enzyme of plant origin of the papain type. This compound is supplied in powdered form containing a soluble diluent for purposes of standardization and is adjusted by the manufacturer to facilitate handling. The material is used at a rate up to about 2 pounds per 100 barrels of beer, depending on the individual characteristics of the beer and the degree of chill haze protection desired. Some breweries prefer compounds containing pepsin to papain. What is known as chill haze in beer is due to the presence of colloidally suspended proteins and precipitated proteins formed on rechilling or excessively chilling the packaged beer. Both papain and pepsin peptonize proteins or catalyze depolymerization through hydrolysis. It is generally agreed that papain catalyzes depolymerization of proteins a t the isoelectric point, whereas pepsin catalyzes protonated proteins, but this important difference is sometimes overlooked even by chemists. Since the enzyme is added a t 32' F., the maximum concentration of the proteins would be expected to be in solution; apparently two things take place with the addition of papain: 1. Depolymerization of native proteins, resulting in more soluble peptones and polypeptides and therefore a more stable solution of the proteins. 2. Depolymerization of the protein fraction of tannin-protein complexes, resulting in more soluble polypeptides and/or peptones and a new tannin-protein complex with a n isoelectric point higher than the p H of the beer.
The complex then precipitates out, leaving a stable solution, as evidenced by the precipitate formed in brilliantly filtered beer when treated with papain. Keg beer does not receive chillproofing since it is normally consumed within a short time and is not generally subjected to excessive chilling. Control of oxidation and elimination of oxygen after the fermentation and in the finishing process are important in the prevention of oxidation haze. Some investigators believe this is accomplished by a change in rH. To retard the development of oxidation haze, elimination of oxygen after fermentation and during finishing is generally relied on as an effective treatment. Beer remains in the finishing tanks (300- to 625-barrel capacity) shown in Figure 4, for a period of 10 to 14 days. During the early part of this storage period the beer is completely carbonated to a level of 2.7 volumes of carbon dioxide per volume of beer. This is accomplished by introducing carbon dioxide a t 20 to 25 pounds per square inch pressure through porous clay cylinders (3OE)in permanent sockets attached to the tank bottoms. When ready for packaging the beer is filtered through pulp filters (8E) consisting essentially of cotton fibers and asbestos. After each filtration this "Filtermass" is removed, mangled, and washed in clear, warm water, then bleached and sterilized a t 160" t o 180" F. with chlorine. The washed pulp then goes directly to a pad-forming machine where i t is compressed a t 80 to 90 pounds per square inch to form new fitter pads. Advantages and disadvantages of this type of filtration, as well a s the diatomaceous earth filters are discussed by de Clerck (3). Keg beer is pumped through a government meter ( d E )directly to the racking machine (title photo) from which the kegs are filled immediately. This machine consists of a horizontal steel cylinder to which the filling arms are connected. A counter pressure of 15 to 20 pounds per square inch is put on the keg and then beer is allowed to flow in, The bung is put in place by hand and kegs are stored in a refrigerated (32" F.) room. Beer for bottling is pumped, also through a government meter ( I S E ) , into bottle storage (essentially a surge tank), termed "government cellar." At the Pearl Brewery, the bottle house is 200 feet from the finishing cellars. To prevent wild or foaming beer prior to or during the bottling operation the government cellar is located immediately below the bottle house. Thus the beer has the minimum distance to travel into the bottling machines directly above,
INDUSTRIAL AND ENGINEERING CHEMISTRY
1270
Item Grain storage bins
hIethod E m p t y , clean, a n d gas x i t h tear pas (chloropicrin, 99wc) Water treatment tanr;r Empty a n d clean coinpletely Varnish 3iash tiin a n d cereai Scrub with broom a n d cooker hot v a t e r Lauter t u n ; grant Scruh with broom a n d h o t water Polish inside and o u t Brew kettles Scrnb \vith broom, hot water, and detergent Clean with caustic soda polish inside and oiit Scrub with broom anrl 1301) Jack hot water ICiihlschiff and i c ~ , l i c : ? - Scnih with broom a n d tions hot water Clean with cairstir soda Wort lines Fliish with live steam Flush with il-ater Fill x i t h 10 t o 13vc caustic Cooler coils and 1 ET.= Clean with antiseptic solution and lint 11.111
.Ai1 t n n k s
Aeer line?
Filter3 Cellar Hoors
Ultraviolet light; Flos.: gln?s filters
Lain-en stones
RnclGing machine
Pasteurizers
I.k?. Bottles Can
