Purpose: The objective of this study was to evaluate the application of HPP on the inactivation of murine norovirus (MNV-1) and bacteriophage MS2 on strawberries and blueberries.
Methods: Fresh strawberries and blueberries (25 g) were spot-inoculated with MNV-1 or MS2, at approximately five and seven log PFU/sample, respectively. Fresh and frozen berries were vacuum-sealed, packaged, and HPP treated at 250, 300, 350, 400, and 600 MPa for 3 minutes, with the initial temperature at 4ºC. After treatment, viruses were extracted and recovered from the samples and quantified by viral plaque assay.
Results: Fresh strawberries and blueberries were inoculated with MNV-1 at 4.7 ± 0.6 and 4.4 ± 0.5 log PFU/sample, respectively. Higher viral inactivation in strawberries was observed as pressure levels increased. At 400 MPa, greater than 4 log reductions were achieved in fresh and frozen strawberries. The inactivation of MNV-1 was significantly lower in fresh and frozen blueberries, with 1.9 ± 0.5 and 2.2 ± 1.2 log reductions at 600 MPa, respectively. MS2 showed high resistance towards HPP, with less than one log reduction observed.
Significance: Effective inactivation of MNV-1 is achievable with HPP treatment for strawberries and blueberries. These results suggest HPP is a promising technology to improve microbial quality while retaining sensorial characteristics of berries.