Hop products with isomerized or reduced iso α-acids intended for use in beer brewing or elsewhere in the food industry
Hop products with isomerized or reduced iso α-acids are dissolved with methanol. The bitter acids are separated through reverse phase high-pressure liquid chromatography (RP-HPLC) and isocratic elution. They are then measured at a wavelength of 270 nm.
This method describes how to evaluate the color and luster of malt as part of a manual inspection procedure.
Malt intended for use in beer brewing or elsewhere in the food industry.
Visual evaluation of the color and luster of malt
Whole hops intended for use in beer brewing or elsewhere in the food industry
Determination of the pH of acidulated malt
Acidulated malt intended for use in beer brewing or elsewhere in the food industry.
The pH value of the Congress wort allows for a cursory estimate of the acidifying capacity of the acidulated malt in question. If a deeper understanding is required, then determining the titratable acidity or the lactic acid content would be necessary.
Acidulated malt intended for use in beer brewing or elsewhere in the food industry
Acidulated malt intended for use in beer brewing or elsewhere in the food industry
L-lactic acid (L-lactate) is oxidized by nicotinamide adenine dinucleotide (NAD) in the presence of L-lactate dehydrogenase (L-LDH) to pyruvic acid. For oxidation of D-lactic acid, the enzyme D-lactate dehydrogenase (D-LDH) is required.
|
L-lactate + NAD+ |
L-LDH
|
pyruvate + NADH + H+ |
|
D-lactate + NAD+ |
D-LDH
|
pyruvate + NADH + H+ |
The equilibrium of these reactions is much closer to lactate. The equilibrium can be shifted towards the pyruvate and NADH side of the equation by removing the pyruvate with the help of the following reaction involving the enzyme glutamate-pyruvate transaminase (GPT) in the presence of L-glutamate.
|
pyruvate + L-glutamate |
GPT
|
L-alanine + α-ketoglutarate |
The amount of NADH formed during the reactions is equivalent to the amount of lactic acid or D-lactic acid; the absorbance is determined photometrically at 334, 340 or 365 nm.