L-cysteine is used in baking to reduce mix times and create a more extensible bread dough.


What is L-cysteine?

L-cysteine is used as a dough conditioner and mix reducer in commercial baking. Well known as a reducing agent, it is an amino acid that relaxes the dough, thus reducing mix times, resulting in dough with improved pan flow.1 It is approved for use by the FDA.2


L-cysteine can be derived from protein sources including goose and duck feathers, human hair, swine bristles, and swine hooves.1 It can also be derived from a plant-based fermentation process.1

The ingredient is also known as E920, and is approved for use in the US, Canada, Australia, New Zealand, and Europe.

Chemical structure of L-Cysteine.

Chemical structure of L-Cysteine.


In bread, L-cysteine is a reducing agent that helps break down the gluten protein in high-protein, high-speed bread systems.

It has the following effects:3

  • Shorter mixing times
  • Lower dough temperatures because of shorter mixing times
  • Less stressed dough, because of shorter mixing times and lower dough temperatures. This produces better-quality dough, and may result in a smaller difference between the beginning and end-of-dough effect.
  • Extensible dough that is more flexible for dividing and rounding with less wear and tear on equipment
  • Better pan flow because of improved dough extensibility
  • Lower volume in some cases

Commercial production

China is the largest producer of L-cysteine. The process starts with boiling the raw material (feathers or hair) in concentrated hydrochloric acid and activated carbon, followed by electrolysis.4

Vegan-grade L-cysteine products are available from some ingredient suppliers. These are manufactured by fermentation from vegetable-based raw materials (such as corn) and inorganic trace elements.4 There are several patents on the process. The products are available as vegetarian, kosher, and halal grade.


Dough softeners such as L-cysteine are added mainly to increase the extensibility of the wheat gluten, especially for “strong” flours with high protein content.4 This is very important for automated production lines, as the addition of it has a positive effect on machinability.4

This ingredient is approved for use up to 0.009 part total L-cysteine per 100 parts of flour as a dough strengthener in yeast-leavened baked goods and baking mixes.2

FDA regulation

L-cysteine is regulated GRAS by the FDA under Title 21, section 184.1271.2


  1.  Baking Association of Canada. “L-CYSTEINE,” http://www.baking.ca/Food%20and%20Nutrition%20Policy%20Revised/L-cysteine.pdf.
  2. US Food and Drug Administration. CFR – Code of Federal Regulations Title 21. Accessdata.fda.gov, www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=184.1271.
  3. Bakerpedia. “Dough Conditioner Ingredients” | Baking Ingredients, bakerpedia.com/ingredients/dough-conditioner-ingredients/.
  4. Hiroyuki, K., et al. “Process for Producing L-lysine by Fermentation.” 15 June 1995.