Origin
Bakeries around the world have modernized their production techniques with high-speed lines. This has posed an issue for wheat growers and flour millers who have being forced to select wheat varieties that give the dough extra strength. However, this is achieved at the expense of dough extensibility and softness. Thus, the use of reducing agents has become a very common practice over the last 25 years, to reduce mixing times.
Function
While oxidizers create bonds to strengthen or mature the dough, reducing agents weaken the gluten structure in the dough by breaking intra and/or intermolecular covalent disulphide bonds between proteins. As a result, S-S bonds disappear and sulphydryl or thiol groups (S-H) are formed. Protein chains become smaller or are broken down, causing the gluten network to become extensible. This is very important when bakeries receive high-protein flours or need to process (mix) strong doughs in a short time to reduce energy consumption.2
Application
Reducing agents are used in the production of different bakery products especially when crop changes and seasonal variations in wheat quality happen. Bakeries must then take quick action to adjust viscoelastic, gas-retention and machining properties in the dough so as to maintain normal plant processing conditions. This would include time, formulation, dividing, sheeting and moulding operations.
The following are a few recommendations when using reducing agents:
- They an be found as tablets. They can also be found along with 1Kg packs of concentrate or base powdered mixes containing multiple minor and micro ingredients.
- As a rule of thumb, the stronger the flour (i.e., the higher its protein content), the higher the amount of reducing agent is needed for the dough to properly develop.
- If dosing in a tablet form, special care must be taken during scaling. The bakery should know the concentration of reducing agent per tablet as this will determine the number of tablets to use at mixing. High doses of these compounds can result in soft, sticky doughs that will be very difficult to handle during the make-up stage.
Types of reducing agents
The more common reducing agents are L-cysteine, sodium bisulphite/sodium metabisulphite and ascorbic acid.
- L-cysteine: Most common agent used in bread. L-cysteine is used at levels up to 90 ppm.
- Sulphites: Commonly used in cookie and cracker production, and require special label declaration in the U.S. if used at a level above 10 ppm.
- Inactivated yeast: Usually added to baked goods at 0.3% to reduce mixing time and enhance nutrition profile.
- Other: protein-based reducing agents may be used. Examples include glutathione (peptide containing cysteine, possibly more effective), and inactivated yeast (natural source of glutathione).
FDA regulation
| Reducing agent | Limit of use |
| L-cysteine | Substance generally recognized as safe (GRAS). It has no limitations on its conditions of use other than current GMPs.
90 ppm or 90 mg per Kg of flour as defined in §170.3(o)(6).3 |
| Sodium bisulphite | Substance generally recognized as safe (GRAS). It has no limitations on its conditions of use other than current GMPs.4 |
| Sodium metabisulphite | |
| Inactivated yeast | Substance generally recognized as safe (GRAS). It has no limitations on its conditions of use other than current GMPs.4 |
References
- Sahi, S.S. “Ascorbic Acid and Redox Agents in Bakery Systems” Bakery Products Science and Technology, 2nd edition, John Wiley & Sons, Ltd, 2014, pp. 183–197.
- Bonomi, F., and Lametti, S. “Thiolomics of the Gluten Protein Network of Wheat Dough” Encyclopedia of Food Grains, 2nd ed., vol. 2, Elsevier Ltd., 2016, pp. 154–155.
- Smith, J. “Preservatives” Food Additives Data Book, 2nd edition, Blackwell Publishing Ltd., 2011, pp. 832–837.
- U.S. Food and Drug Administration. “21 CFR 182 – Direct Food Substances Affirmed As Generally Recognized As Safe.” 1 Apr. 2017, https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=182. Accessed 16 May 2018.