By Robert M. Halcrow
J. E. Siebel Sons’ Co., Inc., Chicago, IL
Published in April 1962
From time to time significant variations occur in analytical data pertaining to the chemical and physical composition of beer from a given plant. In this discussion, we shall dwell mainly on the chemical changes that are sometimes encountered, and shall review some of the checks a brewer can make in his plant with the aid of outside assistance, if necessary, that will help identify the source or sources responsible for these real variations in his product.
It should go without saying that it is not our aim to thoroughly discuss each variable that occurs, but rather it is our intent to review some of the many factors that can bring about variations in beer analysis values. Practical causes rather than theoretical causes are stressed.
Our modern day beers are very delicate in color. Changes in color can often alert the brewer to some irregularity in the process, even though other aspects of his beer analysis are perfectly in line. What are some of the points to check?
- Raw Materials. Cereal adjuncts contribute little or no color. Malt does contribute color; however, with modern malting practices and especially in the case of brewers who have set up malt specifications with their suppliers, it is quite unlikely that color differences can be attributed to the malt; occasionally it might happen.
- Brewhouse Procedures.In creases in beer color can result in the brewhouse processing if the following conditions are permitted to develop:
- Too much water during the mashing-in operation.
- Faulty correction of the brewing water and high pH of the mash; prolonged mashing and/or prolonged sparging procedures.
- Faulty correction of alkaline sparge water.
- Poor kettle boil, possibly due to wet steam or improper handling of the kettle operation; a poor kettle break which affects the hot and cold breaks where much of the coloring substances are eliminated with the trub; local overheating of the kettle, particularly if the wort gravity is high.
- Failure to provide a tannate coating after cleaning and polishing the kettle; in the kettle auto-oxidation takes place under the influence of metal catalysts, such as copper and iron, these metals increasing the absorption of oxygen by wort constituents, particularly at high temperatures, and causing a darkening of the finished beer.
- Difficulties in run-off.
- If for any reason the separation of the hops from the wort should be delayed, or where prolonged con tact of wort with hops is allowed to occur, particularly where alkaline sparge waters are used in the presence of ample access to air. Slight variations during the period of wort cooling should have little or no effect on the final beer color except for hot aeration which increases beer color.
- Some strains of yeast can reduce color more than other strains.
- Use of old, discolored hops.
- Removal of trub during fermentation reduces color; however, beer left too long, especially in open fermenters, will increase in color. Lowering of pH coupled with the reducing action of yeast eliminates certain colored substances from fermenting beer.
- It has been claimed that the same strain of yeast used for a number of generations accumulates coloring substances which are not removed by washing and/or screening. These dark substances may dissolve in fermenting beer under the influence of CO2,. This observation has met with some skepticism.
- Poor biological wort stability can affect color.
Probably the greatest fluctuation in beer color occurs during beer storage processing.
- Oxidation during storage and finishing will darken the beer color.
- Lack of uniform storage periods and improper temperature control can affect color.
- Moderately short beer storage periods followed by good filtration practices has a tendency to lighten beer color.
- Prolonged contact with highly adsorptive materials such as activated carbon and certain precipitating agents can decrease beer color.
- Pasteurization generally darkens beer since it leads to
caramelization of some sugars and also intensifies the effects of oxidation which affect beer color.
- Abnormal amounts of alkali carry-over in bottles discharging from the soaker can darken beer color.
- Beer filled into fresh, chemically cleaned unpitched aluminum kegs has been known in some cases to decrease in color.
It might be noted, as a matter of interest, that some stouts containing large amounts of caramel can show a decrease of color during pasteurization due to a precipitation of caramel.
It is apparent that there are a great many factors in the brewing process that have an influence on the color of the finished product. The above check list by no means exhausts all the factors that can enter into the problem of beer color.
Specific gravity, apparent extract, real extract, alcohol by weight, original extract, real degree of attenuation, apparent degree of attenuation
These routine determinations forming part of a regular beer analysis will be discussed in a collective manner because of the interrelationship which more or less exists between them. In brewery practice measurements are normally made of original extract, apparent extract, alcohol, and degree of attenuation. Apparent extract is calculated from the specific gravity by referring to the A.S.B.C. “Tables Related to Determination of Wort, Beer and Brewing Sugars and Syrups.” It, as well as the other previously named determinations, is important from the standpoint of uniformity. Differences in attenuation can generally be related to changes or abnormalities in the brew house and/or fermentation. Attempts to correlate original extract of the beer with that of wort are misleading because such factors as the conversion of a certain amount of extract to carbon dioxide, the conditions prevailing during fermentation, the amount of yeast produced during fermentation, evaporative losses and dilution with water also play a role. The amount of alcohol in beer is important, especially with regard to those brewers making a 3.2 percent beer. While the limit degree of attenuation is not usually included in a regular beer analysis, the difference between the real degree of attenuation and limit degree of attenuation should remain relatively constant. Abnormal differences in limit attenuation usually indicate changes in the sugar composition of the wort due to raw materials and/or changes in mashing procedure. Uneven temperatures across the mash bed during mixing can vary the sugar composition of the wort.
The reducing sugar content should remain uniform with respect to the composition of the beer. It is supposed to represent the amount of fermentable sugars remaining in the beer; actually, this is not true in all cases. Reducing sugars can include certain dextrins, trisaccharides, and pentosans which are not fermentable by a normal brewer’s yeast. Differences in reducing sugar content can be associated with:
- restricted fermentation;
- possible changes in the fermenting power of the yeast; and
- changes in brewhouse procedure and materials.
The protein figure reported in a beer analysis really does not tell the brewer very much. The value should be relatively consistent for a given beer. However, it does not follow that a given beer showing a higher protein content is colloidally more unstable in comparison to a beer showing a lower figure. The development of hazes in beer, particularly the chill haze, depends on the type (rather than the amount) of the proteins in beer.
Variations in protein content of a beer can result from:
- Differences in malt.
- Improper water correction, unduly long mashing procedures, and poor kettle operations.
- A sluggish fermentation which interferes with proper elimination of protein.
- Non-uniform cellar temperatures and uneven periods of storage.
- At times an increase in pH of a finished beer is associated with a slightly increased protein content however, this association does not always hold true.
It is quite conceivable that some day the various types of protein and protein complexes contained in a beer will be readily determined. The role which these proteins and their complexes play in the formation of various hazes will then be finally solved; when that day arrives, a significant contribution will have been made toward a more complete under standing of the composition of beer. The fundamental studies, such as those undertaken by the B.I.R.I. and others, are vitally important in this connection.
The term dextrin as applied to a beer analysis is somewhat of a misnomer. Dextrins are determined as the differences between acid hydrolyzed saccharides and reducing sugars. Undoubtedly many of the hydrolyzed saccharides are not dextrins. The importance of dextrins in a beer analysis is questionable at this time.
Certainly no starch or higher polysaccharides should be present in beer. We quite often find a trace of erythrodextrin in beer but, as long as it is present in traces, it need not give cause for alarm. Where it is found as a “plain trace” in beer it would be wise to check into mashing and lautering procedures, for quite often, if the sparge water is too hot or sparge waters high in alkalinity are used, an iodine reaction can be noted in the finished beer. Old, worn out mashing equipment can also be responsible in part for this condition. A carry-over of iodine reacting material in wort is often eliminated during the course of fermentation. When the old-time brewer came across this condition, he often added a malt infusion to the fermenting wort in order to convert the remaining iodine-reactive substances.
Acidity is generally reported in terms of lactic acid, though a great number of other organic and inorganic acids are involved. The acidity figure should be reasonably constant, though slight fluctuations can be expected.
Various strains of yeast, as well as lack of proper wort aeration, can affect acidity.
Abnormally high acidity can be an indication of bacterial infection of the wort and/or beer. Ordinarily it is not a sensitive type of test, because long before titrable acidity creeps up, the palate detects the microbial disturbance; indeed infected beers often show but a small increase in measurable acidity. Some brewers claim that lower acidities of, say, 0.12 percent produce a smoother beer than, say, a beer acidity of 0.17 per cent; much depends on the character of the product.
All-malt beers can be expected to produce higher amounts of acidity in beer.
A yeast that tends to flocculate early could be responsible for higher acidity.
We have found that the main reasons for increased acidity in many beers are poor biological wort stability and poor yeast performance.
The pH value of a beer is of considerable importance. Increased pH can, in some cases, bring about an undesirable effect in the palate appeal of the product.
Often improper or unnecessary acidification of the mash can increase the pH of finished beer by increasing the production of nitrogenous degradation products and phosphates which act as buffers. The age of the malt and the sulfuring conditions can influence the pH.
Poor biological wort stability can prevent the proper drop in pH during fermentation.
The strain and condition of yeast can adversely affect the pH.
The use of lactic acid in cases where the water is high in temporary hardness can cause the formation of calcium lactate, a powerful buffer in the pH range of 4.0 to 5.7.
A cold fermentation produces less acid and, coupled with a reduced as similation of buffering substance by yeast, tends to produce a higher pH in the beer; the same can be said of a defective fermentation. To strive for a low pH in beer, a quantitative limitation of buffering substances must be obtained through judicious water treatment and mashing procedures.
Yeast must be in intimate contact with the fermenting wort to lower the pH. A slight upward adjustment of pitching temperatures and of the maximum temperature during fermentation might have to be resorted to in order to lower the pH. At times a change of yeast might be indicated.
Adjuncts act as diluents and cause a reduction of pH even with sluggish fermentations. A healthy, vigorous fermentation coupled with the use of adjuncts would result in even lower pH values.
Water high in carbonates can in crease pH.
The judicious use of CaSO4 will prevent or inhibit over-production of basic secondary phosphates in the mash.
Air, CO2 Content
The air content in beer should be low and uniform from package to package. High air content in pack aged beer can come from a number of sources, a few of which are:
- Improper elimination of air during cellar processing, and improper safeguards against excessive air pick-up.
- Bottling tank which contains too much air. The maximum amount of air in a bottling tank should not exceed 0.5 cc/12 ounce container and should preferably be lower.
- Improper safeguards against air pick-up during the filling operation.
The carbon dioxide gas volumes should be at a uniform level from package to package. It is important that the proper gas level in relation to a given plant’s beer be maintained from one bottling to the next. The right amount of CO2 gas for a given beer can only be ascertained by checks and observations within the plant. Some beers are quite sensitive to fluctuations in CO ~ gas content with respect to foam formation, flavor, and drinkability.
Foam character of a beer is certainly a very important factor in relation to customer acceptance.
There are various methods of measuring foam, some of which have their pitfalls and are often quite unreliable. Some brewers use the Sigma value as a standard after good correlation has been established between the Sigma value and actual pouring tests. In conjunction with routine beer analysis we place more faith at the present time in the hand pouring test. The hand pouring method used must be standardized or vast differences in results can be obtained.
Poor foam qualities of a beer can stem from a number of causes:
- Over- or under-carbonation.
- Overmodification of malt or slack malt.
- Excessive enzyme activity during mashing.
- Excessive additions of sugar.
- Faulty chillproof treatment.
- Highly adsorptive filtration.
- Oil and grease.
- Turbulent moving of beer, excessive or prolonged use of carbonating stones in a beer tank.
- Residue from cleaning and/or sterilizing compounds‹and many other factors.
Indicator Time Test
The Indicator Time Test can be a useful method to check the state of oxidation of a beer, if it is interpreted in the proper manner. A brewer can achieve a very low I.T.T. in his beer simply by adding a fast reacting reducing agent to his beer in the finishing or bottling cellars. It does not give him the true picture of the degree of oxidation which his beer has undergone earlier in the process.
High I.T.T. values do indicate that a considerable amount of oxidation has occurred during the process.
The use of reducing agents in ruh storage, use of CO2 gas counter pressure, purging of the beer with CO., gas during each transfer, cold cellar temperatures, uniform processing periods, and the reducing action of yeast, all tend to minimize the ad verse effects of oxidation.
The I.T.T. value of a beer can increase considerably after the main fermentation has ceased. Beer should not be left too long, particularly in open fermenters, before transfer.
I.T.T. values can increase during filtration; for this reason, among others, it is of prime importance that all filtrations be conducted at low temperatures.
Variations in cellar temperatures and process time can affect the oxidation state of beers. Packaging operations can increase I.T.T. values.
Packaged beer containing a high amount of air can lose appreciable amounts of hop bittering substances on prolonged storage.
Certain strains of yeast and the amount of yeast produced can vary the amount of hop bitterness lost during fermentation. Yeasts which have changed their flocculating characteristics have an effect on the removal of iso-compounds during fermentation, powdery yeasts removing more iso-compounds than flocculent yeasts. [Recent findings show that flocculent and non-flocculent strains of top and bottom yeast do differ in their ability to remove isohumulones from wort. However, these differences could not be correlated to
- the degree of flocculence of the yeasts,
- their ability to form a yeast head, or
- the amount of yeast crop
An increase in the pH of the finished beer has an effect when correlating isohumulone content to beer flavor.
A high concentration of protein in wort will lead to a greater elimination of hop bitterness; increased gravity has the same effect. Poor kettle break can vary the isohumulone con tent of finished beer.
The effects of oxidation during the cellar process has an influence on the isohumulone content of beer.
Brewing materials in general can contribute varying amounts of S02 to wort; much is lost during mashing and boiling of the kettle.
One authority claims S02 can be formed during fermentation. It is, therefore, important to watch the condition of the yeast. Certain strains appear to produce more S02 than others during fermentation.
Variations in the length of storage and temperature control can affect the amount of S02 in beer, especially if KMS or similar material is added to the beer in cellars.
H2S can be detected by some critical tasters at a level of several ppb. It is claimed that SO2 can be reduced to H2S by aluminum; the influence of the aluminum spot on crowns might partially account for the differences in H2S content sometimes noted from bottle to bottle in the same case of beer. It is also a point worth studying should the use of aluminum cans become more prevalent.
Some brewers claim that the physiological condition of yeast can contribute to the development of H2S in beer.
It has also been stated that brewing materials can contribute to the H2S in beer.
Pasteurization can increase the H2S content. Generally the more severe the pasteurization cycle the greater is the H2S development. This might be due to some sulfur-bearing amino acids and/or proteinaceous substances decomposing on heating at the pH of the beer.
The true H2S odor is generally not detected in normal beers.
“Light struck” beer does not show any significant increase in H2S. Mercaptans tend to increase in amounts, however.
Volatile mercaptans are normal components of beer, contributing to aroma, and they increase on exposure to light.
All common brewing materials contain some volatile mercaptans. Japanese investigators claim the “light struck” flavor in beer is due to the presence of the unsaturated sulfur‹containing substance 3 methyl-2-butenyl mercaptan. They further suggest that this mercaptan is produced by a photochemical re action between the 3-methyl-2-butenyl group in the molecules of humulones and lupulones and unnamed sulphur-containing compounds present in beer.
Studies have shown that the mercaptan level decreases during fermentation and increases during primary and secondary storage.
The iron content of beer should be as low as possible. Under normal conditions, the iron content of fermented beer is below 0.2 ppm. If it is higher in the finished beer, a pick up of iron after fermentation is indicated.
Iron is said to enter more readily in solution in a beer highly saturated with CO2 gas. Highly oxidized beers also dissolve more iron. High amount of iron can contribute to color increase due to an interaction with wort and/or beer tannins and hop constituents.
Sandegren has found both copper and iron in the ash of chill haze and Helm has found iron, along with silica, in the ash of oxidation haze.
Despite the repeated observations of various metals in beer hazes, little is known concerning the actual mechanism whereby metals participate in the formation of such turbidities. It appears that the amount of calcium in chill hazes far exceeds that of any other metal.
The bulk of iron is removed by precipitation of hot and cold trub in the wort and by fermentation. The presence of yeast in storage beer can reduce iron pick-up.
Corrosion in tanks, vessels, fittings, and poor grades of diatomaceous earth and asbestos can contribute iron to beer.
The minimum quantity of metal which can be regarded as dangerous varies from beer to beer.
Most beers are said to be able to tolerate 0.5 ppm copper, as far as haze formation is concerned. How ever, this high figure should be viewed with suspicion.
The cuprous ions show a greater haze producing tendency than do cupric ions. It is, therefore, claimed by some that the addition of reducing agents will increase the change of a haze appearing in beer.
Hops treated with copper-containing insecticides in the field can contribute substantial amounts of copper to the wort.
Differences in the copper content of beers from different breweries are undoubtedly due to dissolution of copper from equipment surfaces. Brass equipment in particular will readily increase the copper content of wort.
In cold wort only a portion of the copper is in the soluble form, a considerable portion being precipitated with the trub. Accordingly, the clarity of the wort entering the fermenter is a factor which could influence the copper content of the yeast grown therein. Certain strains of yeast can withstand higher amounts of copper than others. It has been found that dead yeast cells usually contain higher amounts of copper than living cells. Bad kettle break or rapid flocculation of yeast after fermentation may, among other results, have an effect of retaining more than normal amounts of metal in solution.
Copper is much more readily dissolved from alkaline cleaned surfaces than from acid cleaned surfaces or those which have a protective film. First beer through copper lines to the filler can pickup copper to fairly high levels. Brewers claim copper pickup is greatly reduced if an acid solution is circulated through copper lines before admitting beer.
Some investigators have found no repressive effect on the growth of yeast by 15 ppm and even up to 30 ppm copper in the wort. There is no explanation as yet for this remark able tolerance, though it does seem possible that a large portion of metal ions does not reach the yeast cell at all and is precipitated by the constituents in the fermenting wort and/or else taken into a complex.