[Role of nitrites and nitroso derivatives on the development of abnormal colorations in cheeses. Study of their decomposition].

Nitrites and nitroso compounds have been incriminated in the development of abnormal colourations of "pont-l'évêque". In a preparation of these cheeses nitrites were added either to the milk or during the manufacturing procedures and in all cases were noticed pink or brown stains and bursting of the cheese pulp with formation of cavities. Our results have demonstrated it is possible to break down these nitroso-compounds with an enzyme from yeast. This enzyme detoxifies the medium following a mechanism which has been elucidated. The addition of yeasts to the cheeses during manufacturing helps to accelerate the desintegration process of the coloured compounds and to obtain a uniform shade of the crust and a total absence of deeper stains. We have shown that the nitrites present in the cheeses will form nitroso compounds. The latter are then responsible for the abnormal and irregular stains; their rapid decomposition helps to detoxify the medium as well as ameliorating the aspect of the cheeses.