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Caustic soda

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Caustic soda is the aqueous solution of sodium hydroxide, which is generally admitted for food as additive E 524. The lye is usually commercially available with a concentration of 36 % (proportion of sodium hydroxide). For the production of lye baked goods, a maximum lye concentration of 4 % is required. During baking, the lye reacts with the fermentation gas carbon dioxide, producing soda (sodium carbonate) and neutralising the caustic effect of the lye. The soda produced causes the somewhat soapy taste of the lye baked goods.

Maillard reaction

The Maillard reaction was named after the French natural scientist Louis Camille Maillard, who conducted experiments in 1912 and described reactions of amino acids and glycosides at elevated temperature. It was not until 1953 that the American chemist John E. Hodge was able to describe detailed reaction mechanisms.

The Maillard reaction is a non-enzymatic colouring reaction in which amino compounds (amino acids, peptides, proteins) react with reducing sugars under the influence of heat.

This colouring effect is very typical in the production of lye baked goods. It gives the baked goods the typical crust colour and provides the unmistakable taste.


Preparation and purity of lye

Safety in the preparation of lye is an important factor in reducing the risk of health hazards (chemical burns). Lye concentrates should always be added to water, whether solid or liquid. Any splashes of lye will thus have a low concentration.

The addition of vegetable oil to improve gloss is not advisable, as lye and oil do not form a stable emulsion and – by a chemical reaction – soap and glycerine are formed. Furthermore, the addition of oil can promote formation of streaks on the surface of lye-baked goods if it is not mixed properly.

The container should be cleaned regularly, as soiling may lead to foaming. Mix the lye well before each use to ensure that the dough pieces are evenly lye-soaked. Especially when treating frozen dough pieces with lye, it is advisable to temper the lye. At temperatures above 35° C, however, the resulting vapours have a negative effect on the user’s mucous membranes and respiratory tract.

Lye concentration

The lye concentration can be calculated mathematically. However, a measuring device is still recommended to check the actual concentration present and to determine reliable values. With a hydrometer, the measurement is made via the density and with an EC meter via the electrical conductivity. However, measured values may deviate due to water quality or impurities such as flour or salt. When diluting the caustic soda, note that the proportion is measured by weight and not by volume. Since one litre of 36 % sodium hydroxide solution weighs 1.390 kg at 20° C, the concentration would otherwise be too high (see following table).

The optimal concentration (max. 4 %) of the lye depends on various factors. The length of time the dough pieces remain in the lye, the baking temperature and the baking time have a direct influence on the colouring reaction. The ingredients also play a role. Confectionery yeast doughs, for example, have a higher sugar content. This in turn increases the quantity of sugars available for the Maillard reaction. To prevent this from leading to an increased colouring reaction, a somewhat lower lye concentration is advantageous here.

Lye concentration at different mixing ratios


The dough pieces in the following illustration were treated with different concentrations of lye. There are clear differences in the crust colour and the character of the baked goods.