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People used fermentation, the work of yeasts and bacteria, to raise bread, turn milk into yoghurt and cheese and preserve food for thousands of years before anyone knew microbes existed.

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The story behind the card

In fermentation, yeasts and bacteria break down sugars and give off acids, gases or alcohol. Yeasts, above all Saccharomyces cerevisiae, known as baker's or brewer's yeast, release the carbon dioxide that makes dough rise and the alcohol that turns fruit juice into wine. Lactic-acid bacteria sour milk into yoghurt and cabbage into sauerkraut or kimchi, and the acid keeps harmful microbes away. Residue on pottery from the Neolithic village of Jiahu in China shows a fermented drink of rice, honey and fruit about 9,000 years ago. Many languages took the word yoghurt from Turkish. Only in the 1850s and 1860s did Louis Pasteur show that living microbes cause fermentation, work that led to pasteurisation.

Türkçe oku
İnsanlar mayaların ve bakterilerin varlığından habersizken, binlerce yıl boyunca fermantasyondan yararlanarak ekmek kabarttı, sütü yoğurda ve peynire çevirdi, yiyecekleri bozulmadan sakladı.

Fermantasyonda mayalar ve bakteriler şekerleri parçalar; ortaya asit, gaz ya da alkol çıkar. Başta ekmek ve bira mayası olarak bilinen Saccharomyces cerevisiae olmak üzere mayalar, hamuru kabartan karbondioksiti ve meyve suyunu şaraba çeviren alkolü üretir. Laktik asit bakterileri sütü yoğurda, lahanayı turşuya ya da kimçiye çevirir; oluşan asit zararlı mikropları da uzak tutar. Çin'deki Jiahu adlı Neolitik köyde bulunan çanak çömlek kalıntıları, yaklaşık 9.000 yıl önce pirinç, bal ve meyveden mayalanmış bir içki yapıldığını gösteriyor. Yoğurt sözcüğü de Türkçeden birçok dile geçmiştir. Mayalanmaya canlı mikropların yol açtığını ancak 1850'lerde ve 1860'larda Louis Pasteur gösterdi; bu çalışmalar pastörizasyonun da yolunu açtı.

Sources and further reading

Background reading: Fermentation in food processing
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