Colour EBC (10% w/v solution)
The European Brewery Convention (EBC) is one of the four systems of analysis in use in the malting and brewing industries. To measure colour, the EBC have standard glass discs of 2 – 27 EBC units. These coloured discs are compared to a diluted sample, and provide a numerical value of the samples colour.
To prepare an extract sample for colour measurement, 10g of sample is weighed (weight) into a beaker and made up to 100ml (volume) with water. Therefore a 10% weight/volume solution is prepared. This solution is filtered, and the filtrate is placed in a glass cell and compared to the EBC discs to give a colour value. Darker extracts may require the 10% solution to be further diluted, in order that the colour can be read between 2 and 27 EBC units. The measured colour is then multiplied up according to the dilution factor.
Dextrins are mostly non-fermentable types of sugars, but also contain some very slowly fermentable sugars. In extract production, dextrins are produced because alpha amylase converts starch into dextrins during the mashing stage.
Dextrinising Units (D.U.)
D.U is a measure of alpha amylase only. Diastatic Power (D.P.) D.P is a measure of the starch digesting enzymes present in a product, or more specifically, it is a measure of the combined activities of alpha amylase, beta amylase, and limit dextrinase.
This is a complex set of reactions that take place between amino acids (from protein digestion) and sugars (from starch digestion). The Maillard reactions cause the formation of many products, most of which have some impact on the flavour and colour of an ingredient. The pre-cursors of the Maillard reactions (amino acids and sugars) are formed during the mashing stage of extract production.
Maltose is a 100% fermentable sugar. In extract production, maltose is produced because beta amylase converts starch and some of the dextrinous products of alpha amylase into maltose. This occurs during the mashing stage.
A sample of extract consists mainly of sugars and water, ‘a sugar solution’. Materials that transmit light will also refract (bend) it, but by differing amounts depending on their densities. A measure of the amount to which a substance bends light is its refractive index. Sugar solutions of different solids concentrations have different densities, and therefore also have different refractive indices. Therefore a measure of the refractive index of an extract can be related to the amount of dissolved sugar it contains. The refractometer in the laboratory measures a related function of refractive index and converts it into refractometric solids content for display.
During the production of some specialist coloured extracts, the filtered wort will undergo an additional stage called ultrafiltration. The wort is fed across ultrafiltration membranes under pressure. The membranes consist of a thin sheet of chemically resistant plastic that are semi-permeable. The smaller molecules (i.e. water and sugars) will pass through, the larger molecules and small particles are retained. The larger molecules constitute the ‘dark coloured’ portion of the wort, and the ultrafiltration acts to concentrate the colour of the wort.
During malt extract production, the grist (coarse milled malt) is added to hot water. Sometimes enzymes are also added. This infusion (the ‘mash’) is stirred and heated (mashing) allowing the digestion of the starch, proteins, and additional compounds present in the malt. A range of sugars and protein breakdown products are generated, and are taken into solution, the malt is therefore ‘extracted’. The ‘mash’ is then filtered to remove any insoluble matter. After the mash has been filtered it is referred to as wort. The wort is then evaporated.