Evaluation of the use of encapsulated SE-P47 phage in the control of Salmonella in milk

This study evaluated the potential of the SE-P47 phage, encapsulated by the extrusion method using alginate, as a biopreservative agent against Salmonella Enteritidis in milk. Initially, phage release from capsules was determined in whole (3.5% fat) and semi-skimmed (1.5% fat) UHT milk samples at 25°C. The average phage titers detected in whole milk after 5 and 240 minutes were 6.18 and 6.16 log PFU/g, respectively, with a release rate of 66.78%. In semi-skimmed milk, a phage titer of 7.02 log PFU/g was obtained at 5 minutes, while at 240 minutes, the phage titer reached an average of 7.38 log PFU/g with a 75% release rate. These findings indicate that higher fat content negatively affects phage release. For lytic activity assays, semi-skimmed milk was selected due to its higher release levels. At 4°C, bacterial reductions ranged between 0.45-1.22 log CFU/mL at MOI 1000 and 0.91-1.18 log CFU/mL at MOI 100000. At 25°C, bacterial counts decreased between 2.01 and 3.27 log CFU/mL at MOI 100000, while a higher reduction of 4.03 log CFU/mL was achieved at MOI 1000 after 12 hours. Greater lytic activity at 25°C compared to 4°C was attributed to enhanced phage replication promoted by bacterial growth. In conclusion, the encapsulated phage was shown to exhibit significant inhibitory activity against S. Enteritidis in milk. The existing lytic efficacy has the potential to be enhanced through studies aimed at improving phage release in milk or other food systems.