CHEMISTRY AND BIOCHEMISTRY OF CHEESE AND FERMENTED MILKS^3952 5
Time (h)
Figure 10.11 pH profile of Cheddar during cheese manufacture.although selected by a different protocol, highly selected cultures are also
used for Dutch and Swiss-type cheeses.
Members of three genera are used as cheese starters. For cheeses that are
cooked to a temperature below about 39"C, species of Lactococcus, usually
Lc. lactis ssp. cremoris, are used, i.e. for Cheddar, Dutch, Blue, surface mould
and surface-smear families. For high-cooked varieties, a thermophilic Lac-
tobacillus culture is used, either alone (e.g. Parmesan) or with Streptococcus
saliuarius ssp. therrnophilus (e.g. most Swiss varieties and Mozzarella).
Leuconostoc spp. are included in the starter for some cheese varieties, e.g.
Dutch types; the function is to produce diacetyl and CO, from citrate rather
than acid production.
The selection, propagation and use of starters will not be discussed here.
The interested reader is referred to Cogan and Hill (1993).
The primary function of cheese starter cultures is to produce lactic acid
at a predictable and dependable rate. The metabolism of lactose is sum-
marized in Figure 10.12. Most cheese starters are homofermentative, i.e.
produce only lactic acid, usually the L-isomer; Leuconostoc species are
heteroferrnentative. The products of lactic acid bacteria are summarized in
Table 10.4.
Acid production plays several major roles in cheese manufacture:
0 Controls or prevents the growth of spoilage and pathogenic bacteria.
0 Affects coagulant activity during coagulation and the retention of active
coagulant in the curd.