Visit to Holt’s Derby Brewery, Empire Street, Cheetham, Manchester.

At 5.30am, the mash man opens the hot liquor (water) tank at 200deg.F and lets this into the mash tuns. This dissolves the sugars. Plates on the bottom of the tuns hold back the husks. The temp. is 150 deg F + 0.5 deg. F. This is called the sweet wort.

This temp. encourages activity of the enzyme beta amylase, which only partly breaks down the large starch molecules into maltose sugar molecules. Alpha amylase would attack starch randomly and produce a much larger range of sugars.

Hot water is then added to "sparge" the remnants. That is to remove residual sugars. In this way up to 955 of the possible sugar content is removed for fermentation. Too much sparging would mean that the husk was broken down and the phosphate content would affect the head of the beer.

The wort, with added hops, is then heated by a heat exchanger called a callindria. It is boiled vigorously to:

* Strip out grainy aromas.

* Extract hop material.

* Convert the acid to a different isomer that is more bitter.

* Stop further enzyme activity.

* Concentrate the wort by about 10%

* Form colours.

This container has a slotted base to allow the liquid to filter out past the hops etc. which also act as a sort of filter bed themselves.

The liquid is then cooled by passing it through pipes, alongside which are cold water pipes. The cold water is heated up and is used itself to wash out vessels.

Yeast is then added. This is obtained from previous brew. The present bitter yeast is the product of brewing over the last 150 years and has not been replaced. Lager yeasts (bottom fermenting) are replaced every 15 generations.

Computer monitors the conditions during fermentation closely. The temp. is measured every 0.8sec. and the mix heated or cooled as required so as to maintain ideal fermenting conditions. The specific gravity, which follows the formation of alcohol, is also closely monitored.

This can be done automatically and the brewer can follow this on then screen either at the brewery or at home on his own PC. If any changes are needed e.g. to open or close valves or the control the temp. he can do this at home.

The yeast is removed by vacuum skimming.

Yeast is stored at 40 deg F.

After fermentation, the vessels are washed with 2% and then cold water followed by peracetic acid, which stays, on the walls of the container only to be broken down into the harmless carbon dioxide and water.

Overall a 450 batch uses 9.2 tons of grain, which would have needed 4.5 acres of land.

Every barrel needs 5 barrels of water to make.