CHEESE STARTER CULTURE:

Requirements to cheese starter culture.

The first function of a starter is to adjust acidity pH-value in the milk.  Supplying a larger or smaller amount of lactic acid, which again gives a faster or slower setting, regulates this.

Cheese texture will either be tough and rubbery or softer.  Another function for the starter is to form CO 2, as this is an essential factor for eye formation and for the finish cheese appearance and body.  It's therefore important, not only that the starter convert the lactose to lactic acid, but also that a suitable amount of CO 2 is formed.

Different investigations have shown,  that an eye, is formed by CO 2 in the water phase.  A small air bubble or whey hollow is thought to occur.   When CO 2collects itself at such a hole, the site and form will depend on partly how much CO 2, dissolved in the cheese moisture, the CO 2 partial pressure as well as the cheese mass flexibility and texture.

If a strong CO 2 development occurs at an early stage, then many holes will be formed while a late and slow CO 2  development gives fewer holes.

For a typical round eyed cheese, (Samsø or Danbo/Gouda) a starter, which produces small amounts of CO2, is used. If air production occurs too early, the cheese can be "many holed", pinhole and with jagged holes.

In cheddar and similar cheeses, which shall be acidic or preferably without holes, a starter is used, which has a fast lactic acid production, but which on the other hand does not produce appreciable amount of CO 2.  The stirred and dipped cheese, (Maribo and Havarti) have on the other hand a structure with many small and irregular holes (openings), which are caused by a mechanical treatment.  An early air development can be helpful to hold the curds apart.  In these cheeses the starter must stop producing CO 2 quickly so as not to produce many "round" holes.  In a cheese like Grana, where a closed body is wanted, the CO 2 production is kept to a minimum partly by using a whey culture with poor production of CO 2, and partly by the cheese being manufactured with low moisture, low pH with a high salt content.

The big holes in Emmentaler cheese are obtained by using a starter of Propionic bacteria, which ferment lactate, and storage in a relatively high temperature. 

Note: CO 2 is  Carbon dioxide