Various liquor treatments are available, e.g. ‘Dionic’ Liquids or DWB Grist salts. In most breweries raw liquor will not have the desired analytical specification and suitable liquor treatment will be required.
The composition of the mashing liquor should augment the minerals supplied by raw materials.
Effect on mashing:
• Calcium and magnesium cause a desirable lowering of pH while carbonate and bicarbonate have an adverse effect.
• Certain enzymes, particularly alpha amylase, are stabilised by calcium.
The important ions for beer flavour are sulphate (gives dry flavour), chloride (full and sweet), magnesium (bitter/sour) and sodium, and to a lesser extent, potassium (salt flavour).
Of the range of metals required by yeast, zinc is particularly important.
Some bivalent and trivalent cations, e.g. iron and aluminium, have a deleterious effect on isinglass fining. Calcium, however, may be beneficial.
Levels of nitrite and nitrate should be kept below the statutory limits. The high levels of nitrates in some areas of the country makes their removal essential.
Raw materials also contribute minerals, e.g. potassium and zinc from malt and sodium and chloride from hydrolysed maize syrups.
Range of Values
Typical analytical values of mashing liquor are given in Table 6.
Water supplies should be sampled weekly for alkalinity, calcium and total hardness, nitrate, chloride and total solids/conductivity. Carbonate levels should be checked after every treatment. All constituents should be checked monthly.
The deeper the supply the more consistent is the composition of raw water and quality need not be checked as frequently. If raw water is supplied by an Authority, arrangements must be made to be told of changes in mineral composition.
Adjusting water composition:
• Bicarbonate and carbonate may be removed or reduced by acidification. lime precipitation or ion-exchange.
• Nitrate may be removed by ion-exchange or reverse osmosis although neither process is specific.
• Demineralisation can be carried out by multi-stage ion-exchange.
• Breakdown liquor if not sterilised should be stored above 60°C (140°F) to prevent bacterial infection
Mashinq liquor is analysed using the methods for the examination of Water and Associated Materials, HMSO.
Nitrate – As low as possible
Metals – Zn, Cu, Fe,Mn Less than 1 ppm
All figures are in ppm (mgs/ltr)