In Italy buffalo milk is an important animal product utilized solely
manufacture of Mozzarella cheese. Of an estimated population of 200000
there are ∼25000 controlled animals. The average milk production, expressed
270 d lactation, is 2000 kg/head with average fat and protein contents
of 82·6 and 46·4 g/l respectively (Associazione Italiana
1996). In recent years there
has been a steady increase in the number of dairy buffalo replacing dairy
cows as a
consequence of the European Union quota system.
The cheesemaking qualities of milk depend on many factors, the most
of which are the concentrations of intact casein and fat. Milk in which
casein has been
broken down by proteolytic enzymes is of less value to cheese manufacturers
& Kelly, 1994). Plasmin (EC 18.104.22.168), the most important endogenous
proteinase, occurs in milk together with its inactive proenzyme, plasminogen
& Funke, 1986). Plasmin hydrolyses αs-casein and
β-casein, although κ-casein has
been reported to be resistant (Fox, 1981). However, Andrews & Alichanidis
found κ-casein to be hydrolysed quite rapidly by plasmin. Plasmin
activity is higher
in mastitic than normal milk (Bastian & Brown, 1996). Stage of lactation
plasmin activity: late lactation is associated with higher concentrations
(Gilmore et al. 1995; Baldi et al. 1996). Thus,
plasmin could be a major problem in
herds with seasonal breeding such as buffalo, which progress through lactation
synchrony and are therefore at a similar stage of lactation at a given
The cascade of reactions leading to plasminogen activation is regulated
complex network of molecular interactions between plasminogen activators
EC 22.214.171.124) and at least three types of specific PA inhibitors (PAI-1;
PAI-3; Saksela, 1985; Politis, 1996). There are two types of highly specific
tissue-PA (t-PA) and urokinase-PA (u-PA) (Saksela & Rifkin, 1988).
PA activity is
higher in mastitic than normal milk (Heegaard et al. 1994a).
previous studies on PA in milk were carried out on bovine and caprine milk.
is available on the presence and type of PA in buffalo milk. Thus the objective
present study was to determine the level and type of PA in different fractions
buffalo milk: casein, serum, and somatic cells.