Beer chemistry
The majority of compounds in beer come from the metabolic activities of plants and yeast and so are covered by the fields of biochemistry and organic chemistry.
[2] Four main ingredients are used for making beer in the process of brewing: carbohydrates (from malt), hops, yeast, and water.
The process of brewing beer starts with malting and mashing, which breaks down the long carbohydrates in the barley grain into more simple sugars.
The shape of these enzymes, their active site, gives them the unique and powerful ability to speed these degradation reactions to over 100,000 times faster.
However, under industrial anaerobic conditions yeasts cannot use pyruvate, the end products of glycolysis, to generate energy in cellular respiration.
In commercial production, the yeast works in anaerobic conditions to convert pyruvate into ethanol, and does not carbonate beer.
Inert gases are not as soluble in water as carbon dioxide, so they form bubbles that do not grow through Ostwald ripening.
Up to now, chemists using advanced analytical instruments such as gas and high performance liquid chromatographs coupled to mass spectrometers, have discovered over 7,700 different chemical compounds in beers.
As an alternative, organic foam stabilizers are produced by hydrolysis of recovered by-products of beer manufacture, such as spent grains or hops residues.
Cobalt could behave as an inter- or intra-molecular bridge between different polysaccharide molecules (changing their shape or size), or cause some conformational changes[13] of different types of molecules present in solution, affecting their absolute configuration and thus the foam molecular structure and its behavior.
Thorne and Helm (1957) also formulated the hypothesis that cobalt, by being complexed with certain nitrogenous constituents of the beer (e.g., amino acids from malt proteins), might produce surface-active substances inactivating the gaseous nuclei responsible for overfoaming and gushing.
The first issues mentioned in the literature were reported in Canada in the middle of the sixties after an accidental overdosage in the Dow Breweries in Quebec City.
[20] A cat urine smell and flavor called ribes, named for the genus of the black currant, tends to develop and peak.
These may come in the form of oxygen free radicals, for example, which can change the chemical structures of compounds in beer that give them their taste.
[22] Oxygen radicals can cause increased concentrations of aldehydes from the Strecker degradation reactions of amino acids in beer.
Beer will develop an off-flavor during storage because of many factors, including sunlight and the amount of oxygen in the headspace of the bottle.
This is called colloidal stability (haze formation) and is typically caused by the raw materials used during the brewing process.
Philip Wietstock et al. performed experiments to test what causes the formation of Strecker aldehydes during storage.
Wietstock concludes that capping beers with oxygen barrier crown corks will diminish Strecker aldehyde formation.
[26] The carbonyl compounds, as stated previously in the Wietstock experiments, will create Strecker aldehydes, which tend to cause a green apple flavor.
A study done by Charles Bamforth and Roy Parsons (1985) also confirms that beer staling flavors are caused by various carbonyl compounds.
They also tested the hypothesis that soybean extracts included in the fermenting wort enhance the shelf life of beer flavor.
