Chlorine

Chlorine gas was used historically as a flour bleaching and ageing agent, capable of rapidly whitening flour and improving its baking performance by oxidising carotenoid pigments (responsible for the natural yellow tint of freshly milled flour) and modifying gluten structure. These effects could in weeks what natural ageing would achieve over months, making chlorine treatment economically attractive for industrial flour processing.

No active JECFA ADI is maintained for chlorine as a flour treatment agent, as its use in this context has been progressively restricted or banned in many major jurisdictions. The EU banned chlorine treatment of flour in 1997 on the grounds of safety concerns related to chlorination by-products formed when chlorine reacts with natural flour components. In the United States, chlorine is still permitted for bleaching cake flour only, under strictly controlled conditions.

In the EU, E925 is not currently authorised for flour treatment for bread, reflecting the precautionary approach taken to chlorination by-products. Consumers purchasing EU flour or bread made from EU flour are not exposed to this treatment. It remains relevant for labelling purposes in imported products from markets where it is still permitted, and consumers seeking unbleached flour produced without chemical treatment may look for products specifically labelled as unbleached or stone-ground. The historical use of chlorine in flour illustrates the evolution of food additive policy as safety evidence and analytical capabilities improved.