Introduction

Here is a very small excerpt from the first draft of the introduction to my thesis. Despite the fact that my PhD. is being paid for by a large brewing company, I'm not a brewing expert per se. Maybe you'll find it interesting, maybe you'll give some feedback.

The Brewing Process

History

The brewing process is thought to have been developed some 6000 years ago by the Sumerian people of Lower Mesopotamia (Hough 1985). The fermentation process helped make normally undrinkable water more potable by lowering pH and increasing alcoholic content, thereby reducing the number of potentially harmful bacteria and increasing the nutritional value, especially in beverages in which the yeast was still present (Hough 1985). As brewing spread into Europe, the addition of hops was added to the process, improving both flavour and aiding preservation (Hornsey 1999).

Malting

Malting is the process whereby cereal grain (usually wheat or barley) is germinated in order that an enzymatic degradation of the grain’s endosperm may occur. This process makes sugars and other cellular components easily extractable from the malt. Once this germination has taken place, the grain is kilned to reduce water content and increase the activity of proteases and amylases. The malt is then milled to produce smaller particles known as grist, which are more accessible to enzymes later in the process(Hough 1985).

Mashing

The grist is placed into a large vessel known as a mash tun, and hot water is added until a porridge-like consistency is reached with a temperature of 55-65°C. Insoluble malt extracts are removed by filtration, and the resulting mixture is referred to as wort. The wort is then boiled in order to sterilize it, and to stop any enzyme activity. Hops are then added to enhance flavour and aid in preservation of the finished product (Hornsey 1999).

Fermentation

During fermentation the sugars in the wort are converted to alcohol by the metabolism of yeast. The process begins when a vessel filled with wort is pitched (inoculated) with yeast at a concentration of approximately 300g hl^-1 (Hornsey 1999). It is important that the fermenter is aerated at the beginning of the brew, as pitched yeasts often contain low levels of the essential membrane sterol, ergosterol (Aries and Kirsop 1977). Synthesis of both ergosterol and the essential unsaturated fatty acid oleic acid require oxygen (Andreasen and Stier 1953). Once fermentation begins, cell density rapidly increases and anaerobic conditions are established, and sugars are fermented to ethanol via the Embden-Meyerhof-Parnas pathway (Hornsey 1999). Once fermentation has ceased, the green beer (beer that has not been aged) is removed for maturation, clarification, satabilisation and packaging (Hough 1985; Hornsey 1999).

There are many factors during this process that can have a profound effect on yeast metabolism and the flavour profile of the final product. These include the sugar and amino acid content of the wort, brewing temperature, availability of metal ions such as zinc and the size and shape of the fermenter (Berry and Watson 1987; Verstrepen et al. 2003a; Swiegers et al. 2006).

I'll post the stuff about flavour compounds a bit later.