Purpose: Our objective was to develop a hot water surface pasteurization process for enhancing microbiological safety of tomatoes.
Methods: Tomatoes were surface-inoculated with Salmonella Poona or Salmonella Montevideo using the dip method and were stored at 13 and 22°C for 24 h prior to processing to allow for strong attachment and/or biofilm formation. Inoculated tomatoes were treated in hot water at 70°C for 3.5 min. Treated and non-treated tomatoes were blended in peptone water and plated on XLT-4 selective medium and incubated at 37°C for 24-48 h prior to enumeration of Salmonella cell densities.
Results: Hot water treatments at 70°C for 3.5 min inactivated in excess of 5 log CFU of Salmonella per g tomato. Tomatoes that were treated and stored at 22°C for 12 days retained their firmness, developed red color (ripened), and had no visible decay as compared to the controls. Temperature penetration profiles indicated that the temperatures of the surface and edible tissues of the tomato were 22 and 48°C below the wash water temperature, respectively.
Significance: These results indicate that surface pasteurization at 70°C for 3.5 min will enhance the microbiological safety of tomatoes and will extend the shelf life of this commodity as well.