摘要：Pannerone cheese is a cow raw milk cheese obtained without starter and salt addition,
which can be classified as a semi-soft cheese with a high fat content. Prolonged holding of moulded
curds at warm room temperatures (~ 30 °C) was identified as having a key role in the cheese
microbiological and chemical composition. Microbial populations were numerous and diverse with
high numbers of lactic acid bacteria and coliforms. Pathogenic bacteria were not detected, while
propionic bacteria and spores of lactate-fermenting clostridia were detected in all samples. Changes
in microbial populations corresponded with key changes in chemical composition. During the first
2 days in the warm room at 30 °C, pH decreased to 4.9 and lactose was completely fermented to
lactic acid. Over the next 4 days, metabolism of lactate to butyric (7.5 g$\cdot $kg$^{-1}$) and propionic (1.7 g$\cdot $kg$^{-1}$) acids with a consequent increase in pH to 5.7 occurred. The importance of the warm
room temperature was demonstrated. The incubation of moulded curd had to be carried out at
temperatures of about 30 °C to obtain the typical fermentation profile. The addition of lysozyme to
the vat milk prevented the formation of high level of butyric acid typical of Pannerone cheese, thus
demonstrating the involvement of lactate-fermenting clostridia in the production of butyric acid.
