All About Yeast

Introduction

Yeast, a living organism, has been around man for thousands of years. Ancient Egyptians used it to leaven their bread and make alcoholic beverages. It wasn't until the 1860's that yeast was discovered, via microscope, to be a living organism. Baker’s yeast came into being at the turn of the 20th century.

There are several categories of yeast:

• Baker’s yeast
• Nutritional yeast
• Brewer’s yeast

Since cooking is the theme, we will restrict our discussion to baker's yeast.

Types of Yeast

Baker's yeast is used in home and commercial baking. There are several kinds of yeasts to choose from:

• Active Dry Yeast
• Instant Dry Yeast (quick rise)
• Instant Dry Yeast for Bread Machine
• Compressed Yeast

Each yeast has its place in baking.

Compressed Yeast

(CY), aka wet yeast or fresh yeast, is generally sold to consumers in block sizes of 2 oz or 8 oz. It has a high moisture content (about 70%) and has a shelf life of 8 weeks since packaging. It must be kept 35 to 38 deg F to maintain its freshness and activity.

Active Dry Yeast

(ADY) has most of the moisture removed from it (about 8% moisture content). This puts the yeast in a semi dormant state which increases the shelf life to about a year. It comes in 3 pack strips or a 4 oz jar. ADY needs hydration (putting in 110 F water for 10 minutes) to work. ADY requires two risings of the dough.

Quick-Rise Yeast

(IDY) is an amalgamation of two strains of yeast to create a superior yeast. IDY will reduce the rise time of dough by up to 50%. IDY does not need hydration to work. Only requires one rising of the dough.

Bread Machine Yeast

(BMY) is a quick rise yeast with ascorbic acid added as a dough conditioner (helps dough stretch better). The granules are very fine so they mix well in a bread machine.

Yeast Conversions

Most of the time one yeast can be substituted for another.

Use 2 parts compressed yeast for 1 part ADY.
Use 3 parts compressed yeast for 1 part IDY or BMY.
Use 1 1/4 parts ADY for 1 part IDY or BMY.
Use 3/4 parts IDY or BMY for 1 part ADY.

Yeast Proportions

Yeast proportions to use are based on the amount of flour in a recipe.

• Use 3/4 tsp ADY for every cup (4 oz) of flour
• Use 1/2 tsp IDY or BMY for every cup of flour