Barley intended for the production of malt is evaluated with regard to pre-germination.
Visible pre-germination is evident at the rootlet and is therefore grounds for rejecting a barley lot. However, after the barley is cleaned and the rootlets are removed, the so-called “hidden pre-germination” can be made visible using the staining methods described below.
Kernels suspected of having pre-germinated are boiled for ½−1 min in a 20 % solution of copper sulfate, allowed to remain for 30 min in the hot solution and are subsequently rinsed with water. The acrospire is stained green, making it clearly visible.
Determination of copper content in beer
This method is also suitable for dark and turbid beers. The turbidity particles must be evenly distributed before sampling.
This method is based on the formation of a yellowish-brown, (insoluble in aqueous medium) copper (II) chelate with zinc benzyl dithiocarbamate (ZDBT), a compound that may be extracted with trichloroethane.
Determination of copper content in beer
This method is suitable for beer
Copper in beer is measured using the AAS technique by directly aspirating the diluted sample into an acetylene oxygen flame; the measurement is carried out at 324.7 nm.
The method describes how to determine the copper content of water using atomic emission spectrometry.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
Boiler feed water for use in the production of beer and other foods
Copper forms a complex with sodium diethyldithiocarbamate with a maximum absorption at 436 nm.
If the copper content is high, turbidity will result. In such cases, the water sample must be diluted. The method is suitable for water with a copper content up to 1 mg/l. An extraction must be performed in order to determine extremely low concentrations of copper.
Foreign organisms in brewery yeasts are primarily obligate beer-spoilage organisms and wild yeasts. This method aims to detect wild yeasts in brewery yeast cultures.
Process samples containing yeast
Brewery yeast cultures cannot grow in the presence of more than 200 ppm copper sulphate (CuSO4) in a culture medium. The majority of wild yeasts are not inhibited by this concentration. This means that a universal yeast medium (e.g. YM) with the addition of 200 ppm CuSO4 can help detect the presence of wild yeasts in bottom- and top-fermenting brewery yeast cultures.