432 DAIRY CHEMISTRY AND BIOCHEMISTRY
Shear rate -
Figure 10.33 Representation of shear stress as a function of shear rate for yoghurt displaying
rheological hysteresis.
Fermented milk products developed by chance but the increased storage
stability and desirable organoleptic properties of such products were soon
appreciated. Special therapeutic properties of yoghurt were claimed by
Metchnikoff in^1910 and have been a controversial subject since. It is now
generally accepted that fermented milk products have nutritional benefits
above those of their gross chemical constituents. It has been documented
that some Lactobacillus spp., and in particular Bifidobacterium spp., con-
tained in yoghurt can colonize the large intestine, reduce its pH and control
the growth of undesirable micro-organisms. Some of these bacteria also
produce probiotics. Yoghurts containing such cultures, often referred to as
bioyoghurt, are enjoying considerable commercial success. Legislation in
many countries specifies a minimum number of viable micro-organisms in
yoghurt.
References
Bosset, J.O. and Gauch, R. (1993) Comparison of the volatile flavour compounds of six
European 'AOC' cheeses by using a new dynamic headspace GC-MS method. Znt. Dairy J.,
3, 359-77.
Caric, M. and Kalab, M. (1993) Processed cheese products, in Cheese: Chemistry, Physics and
Microbiology, 2nd edn. Vol. 2 (ed. P.F. Fox), Elsevier Applied Science, London, pp. 467-505.
Cogan, T.M. and Hill, C. (1993) Cheese starter cultures, in Cheese: Physics, Chemistry and
Microbiology, 2nd edn, Vol. 1 (ed. P.F. Fox), Chapman & Hall, London, pp. 193-255.