Eyes in cheese: a concise review

The biochemistry of gas production in cheese and the factors determining the formation of round holes (eyes) in Emmental-type and Gouda-type cheeses is reviewed. It is shown that starter and adjunct cultures, pH and thermal processing of the curd, salting, ripening temperature etc, dramatically influence the shape, size and distribution of the openness. The propionic acid and citric acid fermentations, leading to the eye formation in these cheeses, also generate various compounds, highly linked to their characteristic flavour. Furthermore, eyes constitute a characteristic sensory feature of Emmental- and Gouda-type cheeses and an identity parameter expected by the consumer. The fact that, in other cheese varieties, citric acid fermentation causes the formation of slits and holes accompanied by a defective flavour should not be confused with the desirable formation of eyes in Emmental- and Gouda-type cheeses. The view is expressed that holes prescription shall be included in the description of these cheese varieties in regulatory texts, such as national or international standards.