# Microencapsulation of Natural Food Antimicrobials: Methods and Applications
## 4 Food Applications of Encapsulated Antimicrobials
### Dairy Products  
Despite efforts towards establishing different regulatory actions throughout the world, listeriosis is still one of the most serious foodborne diseases, with high mortality rates (up to 30%) generated by the psychotrophic pathogen _L. monocytogenes_[109]. The presence of _L. monocytogenes_ in pasteurized milk and ready-to-use dairy products has been reported, indicating the inability of pasteurization alone to eliminate some pathogens [120]. One alternative method is the application of microencapsulated antimicrobials such as nisin in dairy products for further prevention of the growth of pathogens [19,109,115]. The inhibitory effect of free and spray-dried nisin in commercial gum arabic microcapsules has been evaluated, individually and in combination, against _L. monocytogenes_ and _Bacillus cereus_ in skimmed or whole milk over 21 days of refrigerated storage at 6 \(\pm\) 1 \(\mathrm{\SIUnitSymbolCelsius}\)[109]. The combination of both free and encapsulated nisin (0.5 mg/L each) displayed the strongest antilisterial effect (pathogen counts lower than 1.0 log CFU/mL) between 3 and 6 storage days. This result could be explained by the fact that free nisin acted first, followed by the encapsulated nisin that had been released from microcapsules.  
Milk ingredients such as casein and most whey proteins possess negative charges while nisin is positively charged at milk pH (\(\sim\)6.6), resulting in electrostatic and/or hydrophobic bonds between the oppositely charged agents. Nisin-loaded zein microcapsules (400 IU/mL) were more effective at decreasing the _L. monocytogenes_ population in milk containing 2 g per 100 g fat incubated at 25 \(\mathrm{\SIUnitSymbolCelsius}\) compared with free nisin (400 IU/mL) due to the reduction in the interactions of nisin with milk components and its slow release [19].  
Encapsulation can protect nisin from temperature changes. Nisin-loaded vesicles or vesicles immobilized on unilamellar membranes during chemdar cheese making were stable despite temperature cycles. The release of nisin Z from liposomes was higher for noninoculated milk than milk inoculated with _Lactococci_ sp. This could be due to the acidic environment induced by lactococcal cells, which maintained the stability of nisin-loaded liposomes and reduced their release. The amount of milk fat had a significant effect on nisin Z release. Indeed, increasing fat content led to enhanced nisin release. Liposomes were placed between fat globules and the casein matrix in chemdar cheese, resulting in destabilization of liposomes due to the establishment of liposome-fat globule membrane interactions [121]. The encapsulation of nisin in liposomes can be applied as a suitable delivery system in products requiring long storage periods, such as cheese. The antibacterial activity of both liposomal-encapsulated nisin Z and in situ-produced nisin by biovar diacetylactis UL 719 was investigated against bacterial cells of _L. innocua_, _Lactococcus_ spp. and _Lactobacillus casei_ subsp. _casei_ species in a chemdar cheese matrix. Encapsulated peptides exhibited higher growth-inhibitory activity against _L. innocua_ compared to the in situ-produced nisin during 6 month ripening. Thus, liposomal encapsulation had the ability to preserve 90% of nisin activity [115].