Production of unsaturated fatty acids in an internal-ripened cheese

The secondary starter cultures can improve the surface lipid composition in mold-ripened cheese, but the lipids in the internal of cheese had not been converted. In the present study, the domesticated Aspergillus oryzae (A. oryzae) JY309 was inoculated into milk for liquid-state fermentation prior to coagulation. The mycelia of A. oryzae JY309 spread inside the cheese and the saturated fatty acids in the internal of cheese were converted into unsaturated fatty acids (UFAs). To prevent further oxidation of the converted UFAs into off-flavor components, rosemary extract was added to inhibit lipoxygenase activity, and antioxidants were supplemented to prevent lipid peroxidation during ripening. Our results showed that the UFA content of the domesticated A. oryzae JY309 in the internal-ripened cheese reached 6.15 g/100 g on the 20th day of ripening, 1.44-fold higher than that in the surface-ripened cheese. By addition of rosemary extract and antioxidants, 88.1 % (25.1 g/100 g) of UFAs were retained. The above results provide data support for the conversion of internal lipids in cheese.