General Considerations

  • The mashing regime used depends on the plant available and the types and amount of adjuncts employed.
  • The parameters to be specified are the liquor grist ratio, the pH, the time(s) and temperature(s) at the conversion stand(s) and the sparge temperature regime.
  • A temperature programmed mash should provide more soluble and amino nitrogen during mashing than is obtained in a constant temperature infusion.
  • When using constant temperature infusion, the lower the stand temperature the more fermentable the worts and the higher the contents of total and free amino nitrogen.

Range of Values

  • For constant temperature infusion the liquor to grist ratio is typically 2·3 – 2·8 hectolitre per 100 kg (2·1 – 2·6 barrels per quarter).
  • For transferred mashes the liquor to grist ratio is typically 2·7 – 3·3 hectolitre per 100 kg (2·5 – 3·1 barrels per quarter).
  • pH is in the general range 5·0 – 5·5 with an optimum of 5·3· Tolerance on specification is ± 0·1.
  • For constant temperature infusion the initial temperature (initial heat) of the mash is 64° – 67°C (147° – 153°F) (see Appendix 4) and stand time is typically 0·5 to 1·5 hr.
  • During sparging mash stand temperature rises to 70° – 71 °C (158° – 160°F) (see Topic 6).

Operational Protocols

  • Mash temperatures, liquor grist ratios and pH should be reviewed if the grist composition is changed, e.g. with new season’s malt or with change of barley variety.
  • Spent grains should occasionally be examined for residual extract and unconverted starch. In case of difficulty, for example with low extract or slow run-off, grains should be examined for signs of gelatinous beta-glucan.
  • If wort separation is impeded check the sparge/underlet temperatures and the milling of the grist.

Measurement Protocols

  • Most variables are measured in process, e.g. weighing, volume measurement and temperature.
  • Mash and wort pH should be measured without delay on a cooled sample using a standardised pH meter
  • Apparent fermentability of wort is measured using the Institute of Brewing Recommended Method 7·1
  • A sample of spent grains should be taken (IoB Recommended Method 7.2.1) and analysed for moisture (IoB Recommended Method 7.2.2), Soluble Extract (Recommended Method 7.2.3) and Total Available Extract (Recommended Method 7.2.4) The difference between Total Available Extract and Soluble Extract is principally due to, and therefore a close estimate of, the residual starch.