Natamycin eliminates yeasts and moss by contact and is effective in very small concentrations (3-10 ppm). Being very poorly soluble in water and aqueous media, the natamycin tends to remain on the surface of the food to which it is applied, and is very effective in preventing the appearance of yeast and moss on the surface of food. On the other hand, potassium sorbate, another approved amino acid, is soluble in water and, being absorbed by the food, its concentration on the surface where the moss appears is small. What’s more, as potassium sorbate is only fungistatic, any moss will tend to develop.
Numerous studies have demonstrated the effectiveness of natamycin in the surface treatment of cheese in comparison with potassium sorbate. Pugazhenti in 1999 compared natamycin with potassium sorbate. Lower levels of natamycin (5 ppm) were more effective than higher levels of potassium sorbate. Ruig & Van den Berg (1985) observed other advantages of natamycin over potassium sorbate. They found a fall in the quality of the cheese, specifically under the skin, which was more obvious in young cheeses. Interior portions of the cheese were also affected by the migration of the sorbate. Natamycin has no adverse effects on the skin or on the flavour of the cheese. In 1983 Engel, using high-performance liquid chromatography (HPLC), showed that natamycin does not penetrate the cheese and also had a very low effect on the flavour of the cheese and remained mainly on the surface, just where the pollution lies and where the prevention needs occur. Natamycin’s penetration in the cheese depends on the concentration used, the time of storage and the type of cheese.