Experimental cheeses were prepared in triplicate from pasteurized milk
inoculated with Debaryomyces hansenii under aseptic conditions. Three cheesemaking
replicates, with efficient control of environmental parameters (temperature, relative
humidity, atmospheric composition) showed similar ripening characteristics. Deb.
hansenii grew only on the cheese surface, where its oxygen demand was satisfied,
especially during the first 24 h (mean generation time, 5·8 h). Salting in a sterile
saturated brine solution reduced its growth and decreased viability. Growth was
slower after 48 h because of the decrease in ripening temperature (mean generation
time, 94 h). The total count of Deb. hansenii was maximum
(≈3×107 yeasts/mm2) after 6 d ripening and
its viable cell concentration was ≈2×106cfu/mm2. This
difference was due to the ‘non-viability’ of part of the population. The viable
Deb. hansenii concentration was highly correlated
(r2>0·95) with the lactate concentration in the
inner part and with the surface and inner lactose concentrations, up
to day 10 of ripening. This emphasized the importance of the diffusion of carbon
substrate from the inner part to the surface of the cheese during ripening. The pH
of the inner part depended significantly on the lactate and lactose concentrations.
Surface pH was significantly related to inner lactate concentration, temperature and
relative humidity. This also demonstrated the controlling role of carbon source
diffusion.