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Baker's yeast—a live fungus

The discovery of bread

Bread as we know it today is the result of a long evolution that has its roots in the dark ages and the discovery of agricultural grain production. Flat-bread and hard biscuits made of a mixture of wheat and barley were most probably baked over fire during the Stone Age. Then came the moment, thousands of years ago, when man made the discovery that dough would somehow mysteriously rise.

Thus, civilizations started producing bread, wine and beer using this natural process which was later going to be called "fermentation".

The development of fermentation

The first scientific studies about fermentation go back to the invention of the microscope by Dutch scientist Antoine van Leeuwenhoek. At the time, however, van Leeuwenhoek could only group the microorganisms he discovered, some of which were yeasts, under the name "animals".

Researchers had to wait until 1837 to understand that the organisms found in beer were live plant life that multiplied by budding and helped to create alcohol. Pasteur proved that fermentation was caused by living organisms and that the agents responsible for this transformation were found in the yeast cell. In later stages, Pasteur also proved that yeasts were able to exist in anaerobic environments, that they multiplied under the effect of oxygen and were responsible for the process of fermentation in environments where oxygen was not present.

Bread and the history of yeast

Man’s discovery of bread, long since an inevitable part of his daily nutrition, goes back at least five thousand years to the first consumption of a mash made of grains and the first hard biscuits baked.

Bread in antiquity

Bread was born from man's discovery that naturally rising dough could be used to make biscuits and create new palatable tastes. The ancient Egyptians, later the Hebrews, had recipes for hard biscuits baked on slabs placed over wood fires or in kilns. It can be seen in at least fifteen recipes that have survived to our day that yeast was used as an ingredient.

The production of bread soon spread out all over the Middle East. After first becoming acquainted with bread, the ancient Greeks used their creative skills to develop the technique of bread-making to devise a variety of products. The Greeks not only began to use wheat in their bread-making but also barley and for the first time in history, rye. Historical records show that the Greeks produced seventy-two separate varieties of bread!

Following in their footsteps came the Romans (one of the names the Romans were called was "mashers") who rapidly developed their bread-making skills soon after they discovered the art. Stone kilns for baking bread had begun to appear in 5000 B.C. By 30 B.C., there were 329 bread kilns in Rome but it should be added that the owners of these were all Greeks. Even in those days, the preference of the Greeks and Romans was a white bread made from finely sifted wheat flour.

The ancient Roman naturalist Pliny the Elder, who lived in the first century B.C., wrote that the Gauls and the Iberians were famous for the light bread that they made by adding beer foam to their dough, referring to the yeast accumulating on the surface during fermentation.

YEAST

The yeast comes from living unicellular cells from the culture of a pure yeast strain “Saccharomyces cerevisiae”. 1 gr of compressed yeast contains about 10 billion cells.

Yeast cells are spherical or ovoidal forms ranging from 2-3 µm to 20-50 µm in diameter.

1 gr of compressed yeast contains about 10 billion cells.

Inside of about 600 different types of the yeast, only a few of them has an Industrial importance. The yeast used for breadmaking calls “Saccharomyces cerevisiae”.

Approximate yeast composition:

Dry mattermin. %30
Protein/DM (nitrogen x 6.25)40 - 58
Glucids/DM35 - 45
Lipids/DM40 - 60
Mineral matter/DM% 5.0 – 7.5
Vitamins 
Thiamin (B1) 
Riboflavin (B2) 
Pridoxin (B6) 
Niacin (PP) 
B1:0.002 - 0.0015
B2 :0.002 - 0.008
  
B6 :0.002 - 0.006
PP :0.010 - 0.050

FRESH YEAST PRODUCTION

Labaratory step:

Anaerobic fermentation

Industrial step:

  • Raw materials (water, sugar and nutritive sources, oligo elements...)
  • Multiplication in Aerobic conditions
  • Washing and seperation
  • Partial drying
  • Extrusion
  • Cuting, wrapping and paletasing
  • Cooling
  • Transportation

TYPES OF YEAST

  • Fresh Yeast
    • Cream Yeast

      After discontinious multiplication step of yeast production, yeast is separate from the organic waste by sentrifigation system and kept in cream tanks by cooling as a consentrated cream. There are equipments used in process able to transfer and measure the level of the cream yeast. The equipments where the yeast is in contact, are choosen food grade stenless steel quality and installed for a CIP (cleaning in place) system according to the written procedures. The cream tanks are cleaned after beeing empty.

    • Compressed yeast

      In order to produce the traditional type of fresh yeast, the dry matter is increased up to 30 % by removing the water. Its extruded in order to be in homogen form and after cutting in a requested gramage, wrapped with food grade wrapping material. As the shelf life of the compressed yeast is short, the keeping conditions written on amballage should be taken in consideration. (the best : Clean and dry place between 0 –(+4) °C)

      The method and utilisation ratio of compressed yeast changes according to the formula and process used in breadmaking. After utilisation of needed quantity, the rest should be kept in a clean and cold place until the next usage. During the storage, the boxes should be arranged with an air circulation.

  • Dry Yeast
    • Active Dry Yeast

      Active dry yeast is compressed yeast dryed up to 92-94 % of dry matter. Athough is stable due to having less amount of humidity, it should absorbe the humidity of the ambient.Before to use needs to be rehydrated in a warm water (between 35-40 °C) during 10-15 minutes. If cold water used for rehydration, the yeast activity may decrease, in opposite, when hot water used, due to denaturation, yeast can die.

    • Instant Dry Yeast

      The production of Instant dry yeast gives the advantage of not needing reydratation before utilisation. In order to keep its stability for long time, the yeast is packed under vacuum. After opening the sachet, the rest of the yeast should be closed and kept in the fridge and it’s preferable to be consumed within 3-5 days. Instant dry yeast should be mixed with other ingredients in dry form or must be added to the dough after starting of mixing. In order to get the maximum performance from the yeast, the baker shouldn't forget that the yeast is a living cells and should respect the keeping and utilisation conditions given.

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