Written by Charlie Papazian
From Examiner.com You can follow this series there, but please check out other sources, like bjcp.org for taste evaluations, defects and judging standards. This should provide a more complete picture.
(Prof. GA- Is it possible the Examiner missed printing part of this article? Some spaces were blank and descriptions incomplete or somewhat askew. But the information is still interesting.)
Several quantitative variables differentiate one beer from another helping to define beer styles.
During the 1980s and early 90s analytical variables measured by Professor Anton Piendl of the Institut für Bräuerei-Technologie und Mickrobiologie der Technischen Universität München at Weihenstephan established a baseline for identifying beer style characters. More than 500 different beers were analyzed. The data helped American Homebrewers Association and Brewers Association begin its work more than 25 years ago to help develop its current guidelines for beer types. Professor Piendl’s work was published over a 13 years period in the 1980s and 1990s in the German brewing journal Brauindustrie. Here is a list of the values he measured.
Original Gravity (Balling) – measures the density and sugar content of unfermented beer
Alcohol – (This space left blank by the writer. “ABV” is the usual term used. Although not that accurate, it can be assessed by final gravity, or FG. A few brewer use “proof” but that term really should be used for distilled beverages- Prof. GA)
Real Extract – exact measure of the density of a liquid.
Protein – some types of proteins are essential for healthy yeast fermentation. – Raw Protein, Free Amino Nitrogen, Proline
Minerals – Minerals have a profound effect on beer characte. – Potassium, Sodium, Calcium, Magnesium, Total Phosphorus, Sulfate, Chloride, Silicate, Nitrate, Copper, Iron, Manganese, Zinc
Vitamins – mostly derived from yeast; not currently a determinate for beer style. – Thiamin, Riboflavin, Pyridoxine, Pantothenic Acid, Niacin, Biotin
Organic Acids – Pyruvate, Citrate, Malate, L-Lactate, D-Lactate, Acetate, Gluconate
Total Polyphenols– some phenols are desirable in certain beer types. Other phenols can effect mouthfeel, aroma and flavor, both favorably and unfavorably.
Bitterness – analytically measured bitterness is only one indication of perceived beer bitterness
Dissolved Carbon Dioxide – amount of carbonation
Fermentation By-Products (each having different aromatic and flavor character). – Glycerol, n-Propyl Alcohol, i-Butly Alcohol, i-Amyl Alcohols, 2-Phenyl Ethanol, Ethyl Acetate, i-Amyl Acetate, Acetaldehyde, Diacetyl, 2,3-Pentanedione, Total Sulfur Dioxide
Apparent Degree of Fermentation – an approximate measure of the final density of beer after fermentation is complete
Attenuation Limit, Apparent – measure of fermentation under ideal and forced conditions
Color- (Note: author wrote nothing here. Usually rated by SRM in competitions. -Prof GA)
Note: Professor Piendl did not assess hop aroma in his research. Then it was not a significant factor for most beer styles in the 1980s.