Age Related Changes in the Microstructure of Mozzarella Cheese

Changes that occurred in the microstructure of low-moistu re, part skim Mozzarella made with a mixed starter consisting of Streptococcus sa/ivarius ssp. thermophil us and Lacwbacillus delbrueckii ssp. bulgaricus and coagulated with fermentation -produced chymosin , were examined during 50 days of ripening at 4 °C. Im mediately after manufac ture (day 3), a homogeneous and continuous phase of amorphous paracasein represented a three-dimensional protein network in the cheese. A large number of irregularly shaped and sized microcavi ties were present. During 50 days of aging , an increase in the porosity of the defatted paracasein matrix was apparent. These changes were coincidental with a fourfold increase in water-soluble nitrogen (from approximately 2 to 8 % of total N) and hydrolysis of approximately 50 % of a 1 .-casein. It is suggested that the confluence of adjoining microcavities that occurred progressively throughout storage may be due to proteolysis or C02 production by the starter culture. Key \Vords : Mozzarella, cheese, struc ture , casein, proteolysis, fat globule, chymosin, scanning electron