What affect yeast has on bread making?

Ryan Pow

Investigation: What affect yeast has

On bread making

Aim: My aim is to do a study on yeast and experiment what affect yeast has on the making of bread.

Research: Yeast, any of a number of microscopic, one-celled fungi important for their ability to ferment carbohydrates in various substances. Yeasts in general are widespread in nature, occurring in the soil and on plants. Most cultivated yeasts belong to the genus Saccharomyces; those known as brewer's yeasts are strains of Saccharomyces cerevisiae. For a discussion of the physiology and reproductive behaviour of yeasts, see Fungi: Classification: Ascomycota.

Yeasts have been used since prehistoric times in the making of bread and wine, but their cultivation and use in large quantities was put on a scientific basis by the work of the French microbiologist Louis Pasteur in the 19th century. Today they are used industrially in a wide range of fermentation processes; medicinally, as a source of B-complex vitamins and thiamine and as a stage in the production of various antibiotics and steroid hormones; and as animal feed and foodstuff for humans.

Pure yeast cultures are grown in a medium of sugars, nitrogen sources, minerals, and water. The final product may take the form of dried yeast cells, or the yeast may be pressed into cakes with some starchy material. When a batch of yeast for baking, medicinal, or food purposes is completed, the medium in which the yeast was grown is discarded. In the making of wines, beers, spirits, and industrial alcohol, however, the fermented medium is the desired product, and the yeast itself is discarded or used to make animal feed.

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