Erica Vonasek (Dept. of Biological and Agricultural Engineering, UC Davis), Angela Choi (Dept. of Food Science & Technology, UC Davis), Juan Sanchez (Dept. of Biological and Agricultural Engineering, UC Davis), and Dr. Nitin Nitin (Depts of Biological and Agricultural Engineering and Food Science & Technology, UC Davis)
Controlling and eliminating common bacterial pathogens like E. coli 0157:H7 and Salmonella enterica in fresh produce is a significant challenge. This study aims to develop food grade formulations for encapsulation and controlled release of bacteriophages (phages) on fresh fruits and vegetables. Phage treatment takes advantage of phages’ extreme host specificity, ability to replicate and generate more phages, and natural ability to mutate to defeat host defense mechanisms. This research is unique as it demonstrates the integration of phages with edible coatings to form a bacterial pathogen specific antimicrobial packaging material. In order to encapsulate and control release rate of phages, a dip coating formulation using the food by-product whey protein was developed and evaluated for loading efficiency, phage stability in cold storage, antimicrobial efficacy, and phage activity post simulated digestion. These dip coatings were evaluated on cut apples, cut cucumbers, whole cherry tomatoes, and 18 cm by 18 cm thin glass squares as a model surface. Phage loading at 5log, 7log, and 9log PFU per cm2 demonstrate high loading efficiencies, with greater than 80% efficiency in cut cucumbers and glass. Phages remain stable over 1 week in cold storage (4 degrees C), with less than 1 log PFU loss in both cucumbers and glass. The dip coatings demonstrate antimicrobial efficacy in glass and whole cherry tomatoes. The current results show that using dip coatings can store and release phage to food surfaces and control pathogen growth.