General Science

  • noun the process by which organic compounds such as carbohydrates are broken down by enzymes from microorganisms such as yeasts to produce energy


  • noun the process whereby carbohydrates are broken down by enzymes from yeast and produce heat and alcohol. In making silage, fermentation is essentially the breaking down of carbohydrates and proteins by aerobic and then anaerobic bacteria.


  • The process whereby a microorganism such as a yeast, fungi, lactobacillus, etc. breaks down an energy source (starch, sugar, protein, etc.) in the absence of air, into smaller molecules such as alcohol, acetic acid, lactic acid, etc. thus gaining the energy necessary for growth and reproduction. The process is important in the production of many foods such as yoghurt, cheese, soya sauce, tempeh, vinegar, sauerkraut, etc.


  • noun a chemical change brought about in liquids usually leading to the production of alcohol


  • the chemical process during which the juice from grapes is turned into alcoholic wine. There are two stages of fermentation that can occur. The first stage, called primary or alcoholic fermentation, is the process in which the sugars within the grape juice are converted into alcohol by a catalytic reaction started and controlled by the enzymes in yeast. This first stage of fermentation stops either when the sugar has all been converted or when the alcoholic content is strong enough to kill off the enzymes in the yeast (over 15 per cent alcohol per unit volume). The second stage, called malolactic fermentation, occurs when the malic acid in the wine is converted into a less astringent lactic acid with a by-product of carbon dioxide gas. Almost all red wines see both stages of fermentation, but producers of white wine often prevent malolactic fermentation to ensure that the wine tastes crisp and sharp. This second-stage fermentation is also avoided when the grapes are overripe and too sweet.