Type of Bread Yeasts - Different Type, Different Action.....

 

 

Saccharomyces cerevisiae is the common name for the strain of baker’s yeast, commonly used as a leavening agent in bread product. Where yeast converts the fermentable sugars present in the dough into carbon dioxide and ethanol.

Type of yeast based on form, moisture content and handling requirement:

1.    Cream Yeast

Cream yeast is yeast slurries where yeast cells are suspended in liquid phase. Its primary use in industrial bakeries with special high-volume dispensing and mixing equipment and it is not available for small bakery or home use.

2.     Compressed Yeast

Compressed is essentially cream yeast with most of the liquid removed. It is perishable, poor keeping quality, soft solid, beige color, wrapped with foil in small block to larger block from for bulk usage.

3.     Active Dry Yeast

Active dry yeast is consist of coarse oblong granules of yeast, with live yeast cells encapsulated in thick jacket of dry, dead cells with some growth medium. Under most condition, active dry yeast must be first proofed or rehydrated. It has good keeping properties which can be stored at room temperature for a year or frozen for more than a decade.

4.     Instant Yeast

Instant yeast appears similar to active dry yeast, but has smaller granules with substantially higher percentage of live cells per comparable unit volume. It is more perishable than active dry yeast, but also does not require rehydration and can usually be added directly to all but the driest dough. Instant yeast generally has a small of ascorbic acid added as a preservative.

5.     Rapid Rise Yeast.

Rapid-rise yeast is a variety of dried yeast (usually a form of instant yeast) that is of smaller granular size, thus is dissolves faster in dough and it provides greater carbon dioxide output to allow faster rising. 

Yeast produces carbon dioxide gas in bread making by fermenting the sugars that are present in the ingredients or the formulation. The basic reaction is represented in the following manner:

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

Glucose → ethyl alcohol + carbon dioxide

The yeast cell contains large numbers of enzymes which are required for the fermentation and respiration. These enzyme are held within the cell, provide the cell wall remains intact. About 14 different enzymes are involved in the fermentation process.

When dough is made the yeast first feeds on the naturally occurring sugars in the flour and formula (glucose and sucrose). As these are used up the enzyme complex begins to provide more sugars by breaking down other flour components. Damage starch take important part on this action because will convert to maltose. If flour and bread formula not provide enough substrate (food) for yeast, then yeast will stop working and carbon dioxide production will cease.