Optimization of wall material for phage encapsulation via freeze-drying and antimicrobial efficacy of microencapsulated phage against Salmonella.

Microencapsulated phage as dry powder provides a protection to the phage particles from the harsh conditions while improving efficacy for controlling Salmonella. In this study, wall materials for phage encapsulation were optimized by altering the ratios of whey protein isolate (WPI) and trehalose prior to freeze-drying. Combination of WPI/trehalose at ratio of 3:1 (w/w) represented the optimal formulation with the highest encapsulation efficiency (91.9%). Fourier transform infrared spectroscopy analysis showed H-bonding in the mixture system and glass transition temperature presented at 63.43 °C. Encapsulated form showed the phage survivability of > 90% after 5 h of exposure to pH 1.5, 3.5, 5.5, 7.5 and 9.5. Phages in the non-encapsulated form could not survive at pH 1.5. In addition, microencapsulated phage showed high effectiveness in decreasing the numbers of S. Enteritidis and S. Typhimurium by approximately 1 log CFU/ml at 10 °C and 30 °C for both serovars. Phage powder newly developed in this study provides a convenient form for Salmonella control application and this form exhibits high stability over a wide range of temperatures and pH. This encapsulated phage thus can be used in various food applications without being interfered by physiological acidic or alkaline pH of foods or environments where phages are applied.