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Copyright, 2015
December 13, 2013
Rob
Ingredients
2

Yeast – It’s alive!

A loaf of bread, a soft brioche, doughnuts or even croissants all have one thing in common: they are made with yeast.

A cube of fresh, compressed yeast

A cube of fresh, compressed yeast

What is yeast and how does it work?

First of all, baker’s yeast is a living organism. It is a one-celled fungus to be precise (aka saccharomyces cerevisiae) and it has been instrumental to baking, brewing and wine-making since ancient times.

Yeast in pastry is used to leaven products, providing rise, texture and flavour.

Yeast feeds on carbohydrates (e.g. sugar and starches) and converts them to carbon dioxide (CO2) and ethanol (alcohol) in a process called “fermentation“. To recap:

Yeast + Carbohydrates = Carbon dioxide + ethanol

Once the gluten network has developed in a dough, it will trap the carbon dioxide released by the yeast, leavening the dough and providing the right rise and texture.

yeast-rise

How to use yeast?

First of all, remember three main points about yeast:

  • It needs carbohydrates as food
  • Moisture activates the yeast cells
  • Salt inhibits the growth of yeast

In a recipe, you need to balance well sugar and salt and, most importantly, the yeast should never be in direct contact with them. For this reason, yeast is often dissolved in some water before adding it to the dough. In alternative, you can place the yeast on the flour in the middle of a mixing bowl, then the sugar and salt on opposite sides: this also prevents killing or overfeeding the yeast.

Temperatures as well are very important for yeast:

2°C and lessYeast is inactive
16°C-21°CYeast is active but its action is slow
24°C-35°CBest temperature for yeast activity. You should melt the yeast in water in this temperature range.
55°C-59°CThe yeast dies

The activity of yeast is immediate and continues in the first minutes of baking too, until the dough reaches the temperature at which the yeast dies.

Types and characteristics of yeast

Yeast is mainly available in three forms:

TypeCharacteristicsUsageStorage
Compressed yeastCreamy white colour, fresh yeasty smell, moist (i.e. doughy, not dry, crumbly but not too much)Softened in twice its weight in warm water at around 35° before being added to the dough.2-3 weeks shelf-life, refrigerated. May be frozen and stored for 1 month, but it will lose some of its activity when thawed.
Active dry yeastLooks like a powder, it’s basically yeast without moisture. The absence of moisture makes the yeast inactiveGenerally rehydrated in lukewarm water before being added to the doughCan be stored at room temperature for several months. Should be refrigerated after opening.
Instant dry yeastSame as active dry yeast, but it is more convenient to useCan be added directly to the dry ingredients without rehydrating. The water in the recipe will hydrate it. For firm doughs, instant dry yeast is moistened in 4-5 times its weight of water, to make sure it fully dissolves (deduct this amount of water from the total of the recipe).Can be stored at room temperature for several months. Should be refrigerated after opening.

 

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Active yeastCompressed yeastFermentationIngredientsInstant dry yeastPastry academyTemperaturesYeast
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    WELCOME

    Hi, my name is Rob, I work in IT but I love baking and I also got a pastry diploma. I created this blog to keep track of my journey from complete beginner to world pastry champion (I'm not there yet).

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