Search: Merkmalbeschreibung

The “trueness-to-type” scheme from the Institute of Brewing (IOB) [1] served as the basis for the sensory evaluation scheme according to SCHÖNBERGER (2003, 2004). According to defined sensory objectives, the descriptions of the sensory attributes are selected from the flavor wheel and divided into positive and negative characteristics. The positive attributes are evaluated on a scale from 0 to 3 to 0 (6). A value of 3 signifies the optimal intensity of a particular attribute, and therefore the values 0 and 6 represent weak and strong expressions of the same attribute, respectively. The negative descriptions of sensory attributes are evaluated by the taster on a three-point scale. The difference in the totals between the positive and negative attributes represents the final evaluation of the beer. In addition, the intensity of the attributes can be plotted on a spider diagram. 

Fruit juices

The positive effect of fermented beverages on the human body has been known for centuries. Current beverage trends, like kvass (Russia) and kombucha (Asia), stem from traditions with roots deep in the past. They have always been consumed as healing beverages. Non-alcoholic forms of fermentation employ microorganisms, such as lactic and acetic acid bacteria. They produce organic acids like lactic acid and gluconic acid, which promote digestion and metabolism. Due for the most part to their slightly acidic flavor, these kinds of fermented beverages are popular with consumers as a healthy natural refreshment.

Malt, fruit juice and tea serve as a base for fermented beverages.

As a rule, fermented beverages contain 0.5 – 15 g/l D-gluconic acid.

D-gluconic acid is phosphorylated by adenosine 5'-triphosphate (ATP) in the presence of gluconate kinase to gluconate-6-phosphate

 D-Gluconate + ATP \(^{\underrightarrow{\text{gluconate kinase}}}\) D-gluconate-6-P + ADP

The enzyme 6-phosphogluconate dehydrogenase (6-PGDH) catalyzes the oxidation of gluconate-6-phosphate to ribulose-5-phosphate with nicotinamide adenine dinucleotide phosphate (NADP): 

D-Gluconate-6-phosphate + NADP⁺ \(^{\underrightarrow{6-PGDH}}\) ribulose-5-phosphate + NADPH + H⁺ + CO₂

The amount of NADPH formed during the reaction is proportional to the amount of D-gluconic acid.

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.

D-Isocitrate in the sample is isolated as a barium salt through precipitation. The concentration of D-isocitrate is determined enzymatically. The enzyme isocitrate dehydrogenase (ICDH) catalyzes the oxidative decarboxylation of D-isocitrate to α-ketoglutarate with nicotinamide adenine dinucleotide phosphate (NADP):

D-Isocitrate + NADP⁺ \(^{\underrightarrow{ICDH}}\)α-ketoglutarate + NADPH + CO₂ + H⁺

The amount of NADPH formed is proportional to the amount of D-isocitrate and is measured photometrically through the increase in absorbance.