The abbey of Saint Sixtus of Westvleteren

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Ingredients and different stages of the brewing process

The following pages offer a short description of our beer and supply details on the ingredients and on the different stages of the brewing process.

INGREDIENTS

Since beer consists of water for more than 90%, a high water quality is of paramount importance. Numerous ions in it influence the brewing process to a larger or smaller extent.

Malt is barley soaked in water under the required circumstances (warmth & moisture) and made to partially germinate. At a certain moment the germinating process is restricted by kilning or drying the malt in an oast-house. The term malt is used for barley grains from which the little shoot has been completely removed. During germination the barley secretes enzymes which gradually turn the insoluble starch and protein of the barley into soluble barley sugar and soluble protein. After all, the malting process aims at making the content of the barley soluble in order to make extraction possible while brewing. The composition of barley and other cereals is such that only a small proportion of them can be solved or extracted in water.

The malt provides the larger quantity of the sugars that are converted on fermentation and for the most part it also determines the colour and the taste.

In the St Sixtus Abbey various varieties of two-row summer barley are used.

Hop plants are tendrils that climb up to a height of 7-8 meters. Only non-fertilised flowers of female plants are eligible for the making of beer. The most important hop constituents are the alpha acids. During the boiling of the wort (malted barley mashed with warm water) they undergo a specific thermic isomerisation resulting in the formation of iso-alpha acids which will give the beer its fine bitterness. This formation of iso-alpha acids is seen as a key reaction in the brewing process. Apart from that hop favours the shelf life of the beer. In our brewery both hop pellets and hop extracts are used, i.e. aromatic hop and super A races. We buy our hop from local hop growers in the Poperinge area.

Getting the hopping rate perfect is a real art! The bitterness is the 'make-up' of the beer. It should give the beer its style, elegance and appeal. It should give the customer the desire for seconds, and not second thoughts when trying to get rid of a bitter aftertaste.

Granulated sugar is added to enhance the density of the wort, which in its turn will result in a higher alcohol content.

Yeast is a unicellular micro-organism which converts the sugars in the wort into alcohol and carbon dioxide. From the proteins on the other hand the aromas, taste and olfactory components are formed needed to give each beer its own individual touch.

• Grinding and Crushing the malt
• Brewing
• Filtering the malt mash
• Boiling
• Fermentation
• Process Control
• Storing
• Bottling

Grinding and crushing the malt is aimed at freeing the farinaceous part of the malt grain, so as to allow it to be dissolved more easily. The grinding process however should leave the peels of the grain as intact as possible because they will later serve as a filter bed when the wort is filtered. The remaining fractions of the ground malt on the other hand should be such that a satisfactory yield and an easy filtering are guaranteed. The monks' malt mill at the abbey has a capacity of approximately 1.5 metric tonnes per hour.

After making the mash in which all the starch is reduced to fermentable sugar, the grain mash disintegrates into two components. The first is the watery liquid called wort, the second are the insoluble solid components of the grain, called draff. The two components are separated through filtering, the draff serving as a natural filter bed. A sprinkling system washes out the last remaining extract from the draff and peels.
Once the wort has been completely pumped off to the boiling kettles the draff is removed from the filtering vessel.

When all the wort has been run into the boiling kettles, the performance rate of the wort is established.

The aims of boiling the wort are:

-	Sterilizing the wort. After cooling a pure yeast culture can be added to ferment it into beer.
-	During the boil a lot of water will evaporate. This will make the extract content rise and allows for a concentration yielding the desired density.
-	At 100ºC all possibly remaining enzymes are destroyed. If this were not the case they would remain active during fermentation and would greatly reduce the rich full taste of the beer. Proteins coagulate (this is called the break) which also contributes to stabilizing the wort.
-	Dissolving the useful components of the hop is yet another important function of the boil.

Sugar is added to increase the density of the wort to its desired value.

At the end of the boil the height of the liquid is measured so as to determine the volume. Per brewing day the abbey brews 71.2 hectoliters of wort.

The cooled wort is now pumped to the fermentation room and while it is run into the fermentation tanks yeast is added to it. The most important conversion during beer fermentation is the one in which the yeast enzymes convert sugars into alcohol and carbon dioxide. Numerous by-products however are formed such as organic acids, esters, … For the final aroma of the beer mainly these esters are responsible.

In top-fermenting, between 20-26ºC various stages of the main fermentation process are distinguished: 1. Cauliflower: the tank is covered in white foam. 2. Rocky head: yeast is starting to rise up, mixes with the foam and turns brown and light with great bubbles. 3. Yeasty head : the yeast gradually heaps up in the foamy top and the foam becomes thicker and denser. It is clear that there is more yeast than foam. 4. Skimming point: the main fermentation is over, the foam head is dense and fit to be skimmed off, after which the beer can be pumped off to the storage tanks.
The percentage of sugars that is converted to alcohol is the degree of fermentation or the attenuation. After 4 to 6 days it is high enough and subsequently the beer (the term wort is no longer used now) is cooled and ready to be stored.

Throughout the production process measurements and controls are carried out with regard to the quality and taste of the final product, such as pH, sugar content, attenuation, micro-biological checks,...

During the secondary fermentation and the storing of the beer the following processes take place:

1.	Fermentation of the remaining extract
2.	Saturation of the beer with carbon dioxide A correct carbon dioxide content is of great importance for the taste and the foam retention capacity of the beer.
3.	Clearing the beer During the secondary fermentation and the storing of the beer the sedimentation of yeast cells, protein compounds, resinous hop substances ,... takes place. Through this natural clearing among other things the taste of the beer is refined.
4.	Ripening of the beer Chemical transformations result in the disappearance of the so-called young beer bouquet which gives the beer a sharp, bitter taste. With respect to the upgrading of the taste the formation of esters from the alcohol acids is very important.

Mechanical processes, such as the settling down of the yeast, gradually make the yeasty taste disappear. The rising carbon dioxide bubbles chase off unpleasant volatile bouquet substances such as sulphur compounds.

During the period the beer is stored it becomes softer and purer. Trappist beer remains stored at the abbey in storage tanks for at least three weeks.

The crates are taken to a warm room. Here the beer will be left to referment in the bottle for another fortnight, after which it is ready to be sold to customers.