Yeast performance testing encompasses various procedures for determining either the time required for dough to reach a certain volume or the volume of dough at a given proof time.

Yeast Performance Testing

Also known as yeast activity or gassing power


What is Yeast Performance Testing?

Yeast performance testing encompasses various procedures for determining the time required for dough to reach a certain volume, or the volume of dough at a given proof time. This can be evaluated using standardized procedures.

Yeast performance tests allow bakers to:

  • Adjust yeast levels in dough for optimum volume
  • Predict yeast performance during fermentation and proofing
  • Adjust proofing/fermentation conditions like temperature or humidity
  • Adjust formulation and evaluate the effects of sucrose, water and salt on yeast activity
  • Evaluate the impact of freezing/thawing on yeast tolerance
  • Detect excessive or insufficient levels of starch damage and/or α-amylase activity

How does it work?

Yeast performance tests assess the production of CO2 gas during the fermentation or proofing of a dough sample under standardized formulation, temperature and humidity conditions. The Cereals & Grains Association (AACC International) provides a method for assessing the activity (gas production) of yeast in dough. The method determines:

  • Total or cumulative gas production during a fixed time at a controlled temperature, expressed in mL, or any other equivalent unit such as gauge pressure on a sealed container
  • Gas production rate (mL of gas evolved per minute) at standard barometric pressure.

The method is applicable to the following yeast forms:

  • Compressed yeast (CY) with approximately 30% solids
  • Active dry yeast (ADY) with approximately 92% solids
  • Instant dry yeast (IDY) with approximately 95% solids

Formulas containing 0, 8, and 20% sugar (based on flour weight) can be used for different tests. Dough formulations must be prepared so that equal weights of dough contain equal weights of yeast solids (0.70 g of yeast solids per 100 g of dough). The higher the sugar level, the lower the yeast activity.

Application

The yeast performance test using the AACCI Official Method 89-01.01 below is for compressed and active dry yeasts:1

  • Pretreatment of yeast
    • For CY: 5 min before mixing, weigh 0.01 g of compressed yeast, crumble it into a beaker and soak in distilled water at 70°F (21°C) for yeast rehydration. See formulas in the table below.
    • For ADY: Warm yeast to room temperature for at least 30 min before use....

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