Dairy Chemistry And Biochemistry

428 DAIRY CHEMISTRY AND BIOCHEMISTRY

pizza, e.g. tomato paste, sausage, peppers, spices, anchovies, etc. It may be
possible to produce analogues of other cheeses by adding biochemically or
chemically generated cheese flavours. Apart from the use of some casein
(rennet or acid) in processed cheese blends, cheese analogues, other than
Mozzarella, are not widely used at present. As discussed in section 10.2.8,
the flavour and texture of natural cheeses are very complex and cannot be
simulated readily. The usual approach is to accelerate the ripening of
natural cheese (section 10.2.9), although this approach has enjoyed limited
success to date.

10.6 Cultured milks

Acidified (cultured) milk products may very well be the oldest dairy
products. If removed aseptically from a healthy udder, milk is essentially
sterile but, in practice, milk becomes contaminated by various bacteria,
including lactic acid bacteria (LAB) during milking. During storage, these
contaminants grow at rates dependent on the temperature. LAB probably
dominate the microflora of uncooled milk expressed by hand. Since LAB
are well suited for growth in milk, they grow rapidly at ambient tempera-
ture, metabolizing lactose to lactic acid and reducing the pH of the milk to
the isoelectric point of caseins (about pH 4.6), at which they form a gel
under quiescent conditions, thus producing cultured milks. Such products
have existed since the domestication of dairy animals and some form of
cultured milk is produced throughout the world; the principal products are

Table 10.12 Some typical examples of starter cultures employed in the manufacture of
fermented milks (from Robinson and Tamime, 1993)

Type of culture Product Micro-organisms involved

Mesophilic Taetrnojolk Lactococcus lactis subsp. lactis
Folkjolk
Ymer Lc. his subsp. cremoris
Kefir

Lactococcus lactis subsp. lactis biovar. diacetylactis
Leuconostoc mesenteroides subsp. cremoris
Lc. lactis subsp. lactis biovar. diacetylactis
Kefir grains - thermophilic lactobacilli and
Kluyoeromyces marxianus
Typical fermentation temperature 20-22'C

Thermophilic Yoghurt Streptococcus saloarius subsp. thermophilus
Lactobacillus delbrueckii subsp. bulgaricus
Yakult Lactobacillus casei subsp. casei
Acidophilus milk Lactobacillus acidophilus
A/B milk Lb. acidophilus
A/B yoghurt

Bifdobacterium bifidum
As above plus yoghurt culture
Typical fermentation temperatures 37-42°C