Abstract
In Japan, dehydroacetate and sorbate are authorized as additives to be used as antimicrobial agents for cheese.
On the other hand, application of natamycin for the surface treatment of cheese is allowed in approximately 30 countries. In this investigation, we compared the effectiveness of natamycin and sorbate by treating Gouda-type cheese, specially manufactured for this purpose, with different concentrations of antimicrobials and with different methods of application. The results may be summarized as follows.
1. Natamycin remains on the surface of the cheese not penetrating inside, while sorbate was shown to penetrate inwards, diffusing throughout the cheese.
2. Natamycin showed low effectiveness at the concentration of 5μg/kg (when applied by the coating method), amounting to one-hundredth of that of sorbate.
3. So far as application mode was concerned, coating was more effective than the dipping method, showing the same effect on cheese at about one-fifth concentration compared with the dipping method.
4. When natamycin was applied by the coating method, it could be completely removed by scraping off 5mm of the exterior.
5. The effectiveness of natamycin continued for as long as 8 weeks after application both by the coating and dipping methods, showing a selective effect on molds compared with sorbate. If cheese was not treated with either of the antimicrobials, molding began as early as at two weeks after manufacturing, becoming an obstacle to further ripening and storage of the cheese.
6. Most of the molds on the cheese were identified as strains belonging to genus Penicillium, P. viridicatum and P. roquefortii being the most frequently isolated strains.
