Food containing .gamma.-glutamylcysteine or cysteine is produced by
culturing Candida utilis containing 1% by weight or more of
.gamma.-glutamylcysteine per dry cells in logarithmic growth phase when
cultured in a minimal medium, for example, Candida utilis in which a gene
encoding glutathione synthetase is modified so that intracellular
glutathione synthetase activity is reduced, under a suitable condition
and mixing the obtained culture or a fraction thereof or the culture or a
fraction thereof subjected to heat treatment with a raw material of food
or drink to process food or drink.