US-INACTIVATION of foodborne bacteria: Screening in distilled water and combination with citrus extract in skim milk

•US were used against foodborne bacteria.•US power and duration played a significant role in the antibacterial effect.•Staphylococcus spp., Pseudomonas putida and Salmonella sp. were the most resistant targets.•Staphylococcus can be controlled in skim milk by combining US and citrus extract.

The paper reports on the use of US (ultrasound) as a tool to control the growth of foodborne bacteria. Seventeen microorganisms were inoculated in distilled water, treated by US and the number of survivors was assessed immediately after the treatment; power (20–80%), duration (2–8 min) and pulse (2–6 s) varied according to a fractional design. The results were modeled using a multifactorial ANOVA. Data pinpointed the existence of different levels of resistance/susceptibility, being Staphylococcus spp., and Pseudomonas putida the most resistant microorganisms; moreover, power and time played a major role, whilst pulse was less significant.In a second experiment Ps. putida and Staphylococcus spp. were used as targets for a challenge test in skim milk; a commercial and odorless citrus extract (50 or 100 ppm) was added to control the growth of survivors within the storage at 4 °C. US (80% of power/8 min) acted as a tool in reducing the initial contamination; whilst citrus extract (100 ppm) assured the antibacterial effect of US on Staphylococcus spp. within the storage.