Dairy Chemistry And Biochemistry

418 DAIRY CHEMISTRY AND BIOCHEMISTRY

or a small number of compounds, but it was soon realized that all cheeses
contained essentially the same sapid compounds. Recognition of this led to
the component balance theory, i.e. cheese flavour is due to the concentration
and balance of a range of compounds. Although considerable information
on the flavour compounds in several cheese varieties has been accumulated,
it is not possible to fully describe the flavour of any variety, with the possible
exception of Blue cheeses, the flavour of which is dominated by alkan-2-
ones.
Many cheeses contain the same or similar compounds but at different
concentrations and proportions; chromatograms of some cheese varieties
are shown in Figure 10.25. The principal classes of components present are
aldehydes, ketones, acids, amines, lactones, esters, hydrocarbons and sul-
phur compounds; the latter, e.g. H,S, methanethiol (CH,SH), dimethyl
sulphide (H,C-S-CH,) and dimethyl disulphide (H,C-S-S-CH,), are con-
sidered to be particularly important in Cheddar cheese. The biogenesis of
flavour compounds has been reviewed by Fox et al. (1993, 1996a) and FOX,
Singh and McSweeney (1995).

10.2.9 Accelerated ripening of cheese
Since the ripening of cheese, especially low moisture varieties, is a slow
process, it is expensive in terms of controlled atmosphere storage and stocks.
Ripening is also unpredictable. Hence, there are economic and technological
incentives to accelerate ripening, while retaining or improving characteristic
flavour and texture.
The principal approaches used to accelerate cheese ripening are:

I. Elevated ripening temperatures, especially for Cheddar which is now

usually ripened at 6-8°C; most other varieties are ripened at a higher

temperature, e.g. around 14°C for Dutch types or 20-22°C for Swiss

types and Parmesan, and hence there is little or no scope for increasing

the ripening temperature.

2. Exogenous enzymes, usually proteinases and/or peptidases. For several
   reasons, this approach has had limited success, except for enzyme-
   modified cheeses (EMC). These are usually high-moisture products which
   are used as ingredients for processed cheese, cheese spreads, cheese dips
   or cheese flavourings.


3. Attenuated lactic acid bacteria, e.g. freeze-shocked, heat-shocked or
   lactose-negative mutants.


4. Adjunct starters, especially mesophilic lactobacilli.
   5. Use of fast-lysing starters which die and release their intracellular


5. Genetically modified starters which super-produce certain enzymes; un-

enzymes rapidly.

fortunately, the key enzymes are not yet known.