When a person enjoys a beer at the pub counter or at home, he probably does not imagine how complex the process of brewing beer is.
Well before the brewer gets down to his task, the earth, with a little help from farmers, yields a harvest of barley and hops. The region and the prevailing climatic conditions during the cultivation of these two plants have an important impact on the method that the brewer will use to make his beer.
During this time, the different geological strata of the subsoil shape the water that will be used to prepare the beer. Once the harvest has been completed, the barley will be prepared by the malters, according to the brewer's specifications. The hops will be dried first, then packaged as such or after they have been turned into pellets or extracts - for it is in the latter two forms that hops can be best preserved in time. Although a cocktail of cooking, chemistry and biology, beer brewing also demands rigorous techniques.
In the succession of delicate operations, one finds two principal stages. First of all there is the malting, then the actual brewing. We also discover some of the ingredients which make each type of beer a special sort : water, malt, sugar and hops.
5 operations are necessary for brewing beer :
- in the first place, a source of starch, generally a barley malt;
- the malt grains are then ground into flour to liberate the starch;
- this starch is then transformed into simple sugars;
- yeast is added to transform the sugars into alcohol;
- then, at wish, the liquid is left to rest and then finally filtered.
At the end of this chain of operations, beer is obtained : sweet or bitter; clear or dark; cloudy or clear or sparkling; higher or lower alcohol content. That is the basic recipe used by brewers the world over.
Malt differs from barley by its flakiness, its slightly sweet taste, its aroma, more or less caramel-flavour, and its colour. To produce Orval beer, we use a pale malt and a small proportion of caramel malt. Inaugurated in August 2007, the new brewing hall is really at the cutting edge of new technologies, developed by a German manufacturer in cooperation with Orval brewery and a Belgian university.
Stored in concrete silos, the malt is first cleaned to remove impurities and then crushed using what is known as the wet milling method. During this operation, water from the Mathilde fountain is injected in the crusher at a temperature of 65°C (149°F). This method releases the starch contained in the grains, while retaining optimally the husks that will be used as filtering support. From the crusher, the mash is pumped directly into two newly installed filtering tanks, instead of passing through a mashing vat first. This method was selected when designing the new brewing hall, so as to comply with the English infusion brewing tradition. During mashing, the mixture of malt flour and water is constantly stirred. In former times, the brewer used a rake to perform this operation. The vats are now fitted with motors that drive the mash agitators. The brewer monitors the temperature of the brew closely.
Thanks to the infusion method, a sweet wort is obtained in a few hours. After filtering, this wort is transferred in the boiling vessel, where it is sterilised and flavoured with hops of German and Slovenian origin. An amber coloured wort is obtained in one hour. During this operation, the water favours formed by the boiling are condensed on a heat exchanger, and the energy thus recovered is stored in a 35 m³ water cistern. Stored as hot water at 99°C (210°F), it is used as fuel, thereby reducing the greenhouse gas effect.
As the wort is sterilised when it comes out of the boiling vessel, care must be taken not to contaminate it. This sweet liquid, rich in nitrogenous matter, is actually the preferred prey of bacteria. All the same, it has to be cooled to be brought down to a temperature suitable for pitching, that does not kill the yeast. The boiling wort is cooled very rapidly, away from air, in a previously decontaminated plate cooler. It is in the cold wort that we add liquid sugar candy, before putting the wort in the fermentation tank.
The cooled wort passes through cylindrical/conical fermentation tanks, where pitching yeast prepared from a pure culture is added It was in 1830 that yeasts were identified as causes of fermentation. Once he had isolated these microscopic organisms, the German chemist Mayer named them "saccharomyces," a learned expression for "sugar mushroom." After Pasteur, it was the Dane, Hansen, who isolated the pure yeasts of fermentation at low temperatures, and then the yeasts known as "high," of which we use a very specific strain in Orval. Once pitched, the wort ferments vigorously, is covered with froth, and finally with yeast. The main fermentation lasts 4 to 5 days. The yeasts are active at a temperature between 15 °C and 23°C (56° and 66°F) and come to the surface with the froth during fermentation.
At the end of the fermentation, the young beer, still cloudy, is pumped into the holding tanks, where it matures, fines up, and takes on carbonic gas. The holding period lasts two to three weeks at a temperature of 15°C. It is in these same tanks that the yeasts, which have been very carefully kept in the Brewery laboratory, are added. As they develop in the later stages, they confer on the Orval beer its distinctive, slightly acidulous and so special character. A secondary fermentation in the holding tank gives the beer its incomparable taste, all the more so as fresh hops are added to heighten the bouquet.
Hops, which are late-comers to the symphony of seasoning used to make beer, come from a plant with multiple uses. They were known for their medicinal use, but it was beer brewing that made them a plant cultivated on an industrial scale. The most reputed varieties are the Bavarian Hallertau, the Slovenian Styrian Golding and the Alsacian Strisselspalt. These hops are used to flavour Orval beer. Before bottling, the beer is centrifuged to remove dead yeasts and hop particles in suspension. During this operation, liquid sugar and fresh yeasts are added so as to initiate the refermentation process in the bottle.
The bottling-line is highly mechanised and can attain a rate of 28.000 33-cl bottles of Orval beer per hour. For about 3 to 5 weeks, Orval beer referments in the bottle in storage halls climatised at 15°C (56°F). This process is similar to that of the principal fermentation. The carbonic gas produced by the fermentation saturates the beer and thus contributes to forming a creamy head.
It is only two months after it has been brewed and checked several times for quality that the Orval beer leaves the brewery.
It will bring pleasure to those who drink it if they observe the following rules : Beer, a refined drink for the same reasons as wine, must be stored away from light, at a temperature between 10° and 15°C (46° and 56°F). It should be served at this same temperature and in its special glass, and its sediment should be tasted separately.
The gustative sensations will gain in nuance depending on the age of the beer. Young beer is characterised by a bouquet of fresh hops, with a fruity note and pronounced bitterness, light on the palate and a less firm collar than a beer of six months. The latter will feature a bouquet consisting of a blend of fragrances of yeast and old-fashioned hop. The bitterness is more diffuse and the taste has moved to a slight touch of acidity accompanying yeast and caramel flavours. Served without its sediments, a beer of six months or more, has a particularly bright appearance. It will be less so, if it is served at a temperature below 7°C to 8°C (44° - 45°F).
The brewery indicates the bottling and best-by dates directly on the label. Every consumer can thus easily know the age of an Orval beer, and whether it should be consumed rapidly or less so, depending on whether one likes this beer young, or after a few months or years in the cellar.