Effect of high hydrostatic pressure on the viability of Streptococcus thermophilus bacteriophages isolated from cheese

• Heat resistance of bacteriophages was not related with its pressure resistance.
• Complete killing of S. thermophilus bacteriophages was achieved.
• The inactivation of bacteriophages by HHP fitted the Weibull model well.
• The simplified Weibull model also provided reasonable predictions of lethal data.

The effect of high hydrostatic pressure (HHP) on the inactivation of Streptococcus thermophilus bacteriophages ϕAbc2, ALQ13.2 and DT1 was investigated. Reductions in viability were proportional to pressure (400–600 MPa) and holding time (0–30 min), though the inactivation extent was phage-dependent. HHP treatment at 600 MPa for less than 5 min was sufficient to completely inactivate phages ϕAbc2 and DT1. However, ALQ13.2 only suffered a 3.7-log reduction which showed markedly higher resistance than ϕAbc2 and DT1. Weibull model was applied to describe the inactivation behavior of phages. Regression coefficients (R2), root mean square error (RMSE) and residual plots strongly suggested that Weibull model had a good fit to the data. Additionally, the Weibull models were simplified with a binary model since b values had a linear relationship at 400–600 MPa. The simplified Weibull model provided reasonable predictions of survival data at different pressures for ϕAbc2 and DT1.Industrial relevancePhage infection remains today the most serious and common problem in the manufacture of fermented cheese products. In particular, some S. thermophilus bacteriophages exhibited high thermal resistance, high burst size values and remarkably short latent periods. The use of alternative preservation techniques such as high hydrostatic pressure processing is an efficient method to improve cheese quality and achieve bacteriophages safety. The results showed HHP treatment was capable for complete inactivation of S. thermophilus bacteriophages. The lethal kinetics of S. thermophilus bacteriophages using the Weibull model could help the application of HHP in cheese-making industry.