Purpose: The objective of this research is to control the growth of Listeria monocytogenes and Escherichia coli O104:H4 in contaminated cantaloupes, alfalfa seeds and sprouts respectively, under different storage conditions by using specific non-immobilized and immobilized lytic bacteriophage cocktails.
Methods: Bacteriophage cocktails were immobilized either on positively charged modified cellulose membranes or encapsulated in alginate beads. Phage-treated and non-treated samples were stored for various incubation period and temperatures.
Results: In cantaloupe, when phage cocktail was added in the non-immobilized format, the growth was below the detection limit of the plating technique (< 1 log CFU/gm) after 5 days of storage at 4°C and 12°C. While at 25°C, the growth was below the detection limit after 3 and 6 hours and a 2-log CFU/gm reduction was observed after 24 hours. For the immobilized phage experiment, around 1-log CFU/gm reduction in the bacterial count was observed by the end of the storage period for all tested storage temperatures. For the alfalfa seeds and sprouts experiments, regardless of the phage application technique, sprayed, encapsulated, or impregnated, the growth of E. coli O104:H4 was below the detection limit after 1 hour in seeds and around 1-log reduction in bacterial count was observed on the germinated sprouts by day 5.
Significance: Phage, non-immobilized or immobilized, can be considered as a promising tool to enhance food safety in fresh produce.