Does yeast die when baked?
In this brief guide, we are going to answer the question “Does yeast die when baked” with an in-depth analysis of does yeast die when baked. Moreover, we are going to discuss how long it takes for yeast to die and the factors that are involved that cause the yeast to die.
Yeast is a living microorganism used in fermentation processes that converts sugar and starch into carbon dioxide and alcohol. It is the carbon dioxide that makes baked goods rise (1).
Does yeast die when baked?
Yes, yeast dies when the bread is baked because baking is done at a much higher temperature than required to kill the yeast. Yeast dies at temperatures ranging from 130 to 140°F, depending on the strain of the yeast, while baking is usually done around 200°F.
When bread is fully baked, nearly all the yeast gets killed. Bakers yeast, or S. cerevisiae, the yeast used for baking and brewing purposes, is the most thermotolerant species within the genus Saccharomyces, with the highest optimum 90° F (32.3°C) and maximum 113°F (45.4°C) growth temperatures (2).
Many efforts have been made among scientists in order to select stress-tolerant strains of yeasts, which could survive in higher temperatures or survive after temperature fluctuations, as well as during long frozen storage, in the case of frozen dough (6).
Yeast dies at a specific temperature during baking. Most bread is cooked when the temperature reaches 200°F or 93°C. The temperature at which yeast dies is around 130°F to 140°F (54°C). While making bread yeast ferments the sugar in the flour and releases carbon dioxide. Since the dough is flexible and stretchable, the carbon dioxide is trapped in the dough gluten network (1).
At what temperature does yeast die?
The temperature at which yeast dies is around 140°F. This is the temperature at which yeast is completely inactivated.
At 120°F, yeast starts to die and at a temperature of about 113°F it stops growing, that means, it stops multiplying itself in the dough (2). This temperature is independent of the type of yeast that you use i.e it works for both instant and dry active yeast.
What can lead to yeast death?
Several factors can lead to the death of yeast, beyond high temperatures. These are (1,2,3,7):
- The salt content in the growth medium: salt concentrations of above 2% results in a slight decrease in yeast cell viability
- The sugar content: sugar concentrations of above 30% lead to severe osmotic stress and reduction of yeast survival
- The use of external fermentation enzymes, such as alpha-amylase: the addition of high amounts of enzymes may result in an increased level of damaged starch, which can cause osmotic stress to yeast, leading to a lower yeast viability and lower fermentation rates
- Freezing and frozen storage: freezing can destroy the cellular structure of yeast cells, resulting in the decrease of the cell viability of the yeast after thawing. The cell survival is reduced the longer is the storage
- The pH of the medium: the pH value range in which yeast can grow is of around 2 to 6, whereas in pH values greatly differing from this range, such as above 8.5, reduce the yeast growth and even inactivate the yeast
- Ethanol concentration: to resist high concentration of alcohol in the medium, ethanol-resistant strains of yeast is required
Other FAQs about Yeast which you may be interested in.
What determines yeast growth?
The yeast growth is influenced by various factors related to the characteristics of the medium and characteristics of the yeast strain.
The characteristics of the medium include the pH of the medium or dough, the temperature of growth, the sources of nutrients (dough composition), the concentration of free sugars and the type of sugar, the vitamins and minerals present in the medium and the additives, such as dough enzymes (3).
The characteristics related to the yeast are the yeast optimal growth conditions, which vary depending on the strain. Different yeasts are more or less adapted to stress conditions of heat, cold, concentrations of solutes (salt, sugar, ethanol) and lack of nutrients.
In addition, yeast that has been stored for long periods or undergone frozen storage don´t grow at the same rate as fresh yeast (1).
Does yeast die when part-baked?
The yeast does not die when part-baked because the temperature reached during the production of part-baked or par-baked bread is not sufficient to totally destroy the yeast (8).
Part-baked breads are breads that are partially baked after being proofed to be totally baked in a second stage of production. During the first baking process, the oven baking temperature reaches around 200°C, which would totally kill the yeast.
However, the center temperature of the bread reaches a temperature of only around 90°C, which reduces the viable yeast in the bread, but does not eliminate the yeast population. As a consequence, the bread can grow and be baked in a second stage of production, being fermented during storage and during baking.
In this brief guide, we answered the question “Does yeast die when baked or at high temperatures” with an in-depth analysis of whether yeast dies when baked and part-baked. Moreover, we have discussed how long it takes for yeast to die, and the factors that are involved that cause the yeast to die.
- Struyf, Nore, et al. Bread dough and baker’s yeast: An uplifting synergy. Comprehen Rev Food Sci Food Safe, 2017, 16, 850-867..
- Salvadó, Z., et al. Temperature adaptation markedly determines evolution within the genus Saccharomyces. Appl environ microbiol, 2011, 77, 2292-2302.
- Jach, Monika Elżbieta, et al. Yeast Protein as an Easily Accessible Food Source. Metabol, 2022, 12, 63.
- Ogata, T., et al. Chromosomal location of Lg‐FLO1 in bottom‐fermenting yeast and the FLO5 locus of industrial yeast. J appl microbiol, 2008, 105, 1186-1198.
- Berlowska, Joanna, et al. Utilization of post‐fermentation yeasts for yeast extract production by autolysis: the effect of yeast strain and saponin from Quillaja saponaria. J Inst Brew, 2017, 123, 396-401.
- Lewis, J. G., et al. Stress co-tolerance and trehalose content in baking strains of Saccharomyces cerevisiae. J Ind Microbiol Biotechnol, 1997, 18, 30-36.
- Arroyo-López, F. Noé, et al. Effects of temperature, pH and sugar concentration on the growth parameters of Saccharomyces cerevisiae, S. kudriavzevii and their interspecific hybrid. Inter j food microbiol, 2009, 131, 120-127.
- Almeida, E. L., and Y. K. Chang. Effect of proving time on the quality of frozen pre-baked French style rolls elaborated with the addition of wholegrain flour and enzymes. J Food Sci Technol, 2012, 51, 3390-3396.