The efficient production and maintenance of high concentrations of active bacteriophage under conditions relevant to food production has been a limiting factor in the exploration of the true potential of these organisms for biotechnology, agriculture and medicine. Traditional methods developed for research focus on generating small volumes of highly concentrated samples as the end product of extensive mechanical and osmotic processing, and maintaining these samples under ideal conditions. To function at an industrial scale mandates extensive investment in infrastructure and input materials not feasible for many smaller facilities, which might otherwise contribute to the advancement of research of applied phage biology. To address this need we developed a novel, scalable, generic method for producing high titer psychrophilic phage faster and more efficiently than traditional methods, and generating renewable high yields from single source cultures by propagating phage under refrigeration conditions in which Listeria, Yersinia and their phage grow in equilibrium.

Phage derived by these and traditional methods were then used to evaluate the effects of a number of food-processing and handling factors on phage viability, and the efficacy of select virulent phages as inhibitors of Salmonella and Listeria in raw and processed ready-to-eat food systems. Phage showed significant effects in both systems, but behaved distinctly in response to compositional and temperature factors in host strain and phage species specific manners. Even minor differences in protein sequence among highly similar phage resulted in distinctly different tolerances to thermal and environmental challenges faced during food production.