What is chlorinated flour and how is it used

The treatment of flour with chlorine gas was first identified in the 1920s and was used for the modification of the cakemaking properties of flours for many years in the UK, the USA, Australia, New Zealand, South Africa and many other countries. The use of chlorination for cake flour treatment was withdrawn from the UK in 2000 (The Miscellaneous Food Additive (Amendment) Regulations, 1999). It remains permitted in many other countries.

Chlorine treatment of flour permits the raising of recipe sugar and liquid levels to make the so-called high-ratio cake (i.e. a recipe in which the added sugar and water levels both exceed the flour weight). The principal benefit of the high-ratio cake recipe is that product moisture levels can be increased without adversely affecting the mould-free shelf-life of the product. The higher moisture level confers a more tender eating quality to the final product. If the flour has not been chlorinated and used with a high-ratio recipe then the cake structure will collapse, with loss of crumb structure, the formation of dense, dark coloured streaks and the product eating quality becomes pasty

Chlorine treatment of flour is achieved by mixing and blending the gas through the flour. Typical levels of treatment lie between 1200 and 2500 ppm chlorine based on flour weight. The higher levels are commonly used to treat flour intended for the manufacture of fruited cakes. The gaseous treatment has a number of effects on flour quality but only a small proportion of the gas used actually confers the beneficial effects to the flour. In summary the chlorine gas is used as follows:

• Around 50% of the level used is absorbed by the flour lipids (typically around 2% of the flour mass) but appears to play no significant part in the improving action.

• Around 25% denatures the flour proteins (i.e. prevents the formation of gluten) but plays no major role in the cake-improving effect.

• The remaining 25% or so reacts with the starch granules and this is the main cake-improving effect. It appears that the chlorine reacts with the proteins associated with the starch granules and makes them more hydrophobic. There is also evidence that chlorine treatment increases the exudation of amylose

Fig. 6 Effect of chlorination on cake quality.

from within the starch granules (Telloke, 1986) but that there is no change in the gelatinisation temperature of the starch (Cauvain et al., 1977).

• The action of chlorine is to bleach the flour pigments so that a whiter flour and brighter product crumb colour result.

• The flour pH is lowered and commonly used as a crude measure of the level of chlorination achieved. More accurate assessment of the level of chlorine treatment requires the use of a chloride meter.

In the UK and elsewhere the heat treatment of flours for cake making has replaced chlorination (see 2.9).

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