Method named after the chemist Louis Pasteur (1822-1895) for killing microorganisms in liquids or food that cause spoilage. Pasteur solved a major problem for winegrowers. The bottled wines were often not stable in the bottle. Again and again, secondary fermentation occurred or the wines developed a tang of vinegar or lactic acid. By heating to high temperatures, yeasts, bacteria (e.g. lactic acid, acetic acid, salmonella) and moulds can be killed, thus making the products sterile and durable. However, certain microorganisms require high temperatures. Today, mainly fruit juices (grape juice), vegetable juices, milk and beer are pasteurised. This is done at temperatures between at least 60 and a maximum of 100 °Celsius for varying durations (a few seconds to 30 minutes). The vitamins are largely preserved, but vitamin C is destroyed. Heating above 100 °Celsius to kill heat-resistant bacteria and viruses is called sterilisation.