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The fermentation cellar yield is calculated using the value determined for the amount of extract contained in a batch of wort relative to the amount of extract present in the raw materials used to produce the wort.

As with the DLG score sheet, the individual criteria are assessed on a five-point scale. The criteria judged in the evaluation represent a combination of factors pertaining to the assessment of quality (purity of aroma, purity of flavor, quality of bitterness, overall quality) and intensity (bitterness, hop aroma, fullness, liveliness). It is important to note that with reference to fullness, an optimum score is 3 or 4.

Aside from evaluating the criteria flavor, fullness, liveliness and bitterness, based on the DLG Quality Assessment for Beer (refer to S.590.53.700 Einzelprobenprüfung zur Qualitätskontrolle von Bier - DLG-Prüfschema für Bier), the additional gustatory impressions of the four prevailing Southern German wheat beer styles are examined more closely. Thus, the sensory intensity and quality of the estery, phenolic, yeasty and malty notes in these beers can be assessed. Estery beers exhibit an evident fruitiness, of which the banana-like aroma of isoamyl acetate is the most prevalent. Wheat beers of the phenolic variety impart a clove-like impression, primarily due to 4-vinyl guaiacol, which at higher concentrations can be perceived as medicinal. Yeasty beers can exhibit a wide range of flavor-active fermentation by-products; however, old yeast and sulfur notes tend to dominate. Except of course for malty notes, wheat beers of a more malty or neutral character do not usually possess a distinctive aroma. The criteria are evaluated on a five-point scale, with 5 considered to be “pure” and 1 as “exhibiting major faults”. Scores are also possible in half-point steps.

Fruit juices:

The acid spectrum typical of certain types of fruit are used, along with other criteria, as a basis for recognizing unadulterated fruit juices. Tartaric acid, citric acid and L-malic acid are recorded here, which, with a few exceptions, determine the total acidity of the fruit.

Citric acid occurs as the primary acid in citrus juices and other juices. Orange juice usually contains 3–17 g/l citric acid (AIJN).

In citrus juices, an addition of citric acid can be detected via the citric acid/D-isocitric acid ratio, as this lies within relatively narrow limits. In orange juice, values below 130 are found.

D-isocitric acid is partly present in fruit products as a lactone. The lactone must first be saponified prior to enzymatic determination in order to detect the total D-isocitric acid content.

Malt, wort and beer:

Citric acid is an organic acid and is present in malt and wort and is also produced during fermentation.

Citric acid (citrate) is converted to oxaloacetic acid and acetic acid catalyzed by the enzyme citrate lyase (CL):

Citrate oxaloacetic ^{\(^{\underrightarrow{CL}}\)} acid + acetate

In the presence of the enzymes malate dehydrogenase (MDH) and lactate dehydrogenase (LDH), oxaloacetic acid and its decarboxylation product pyruvic acid are reduced to L-malic acid and L-lactic acid, respectively, by reduced nicotinamide adenine dinucleotide (NADH):

Oxaloacetate + NADH + H^{+ \(^{\underrightarrow{L-MDH}}\)} L-malate + NAD⁺

Pyruvate + NADH + H^{+   \(^{\underrightarrow{L-LDH}}\)}L-lactate + NAD⁺

The sum of the quantity of NADH consumed during the reaction is equivalent to the quantity of citric acid. The absorbance is determined photometrically at 334, 340 or 365 nm.

Higher alcohols and esters in beer are determined by gas chromatography using the headspace method, e.g., the volatile compounds are transferred from the gas space in the sample vial to the GC system for analysis. The method is suitable for beer brewed to any original gravity or to any alcohol content.

Determining the density with a digital density measuring device is performed by the electric excitation of a measurement cell (oscillating U-tube) filled with the solution to be analyzed. As the solution increases in density (corresponding to an increase in mass at the same volume in the measurement cell), this has an effect on the oscillation period (resonance frequency) in the measurement cell. The density can then be calculated from the oscillation period and from this value, the other quantities, e.g., extract content, can be extrapolated [1, 2, 3].