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Different processing sequences of ultrasound and heat were applied for the inactivation of Staphylococcus aureus and Escherichia coli in milk. The changes in whey protein content, particle size, zeta potential, pH, viscosity, and color values were studied to evaluate the effects on the quality of milk. Results indicated ultrasound treatment (600 W, 5 min) with postheating (63 °C 5 min) reduced S. aureus and E. coli by 1.58 and 2.02 log cfu/ml, respectively, but yielded 0.26 and 0.19 log cfu/ml sublethal S. aureus and E. coli. Milk preheated to 63 °C (5 min) followed by ultrasound (600 W, 5 min) showed 1.17 and 1.68 log reductions for S. aureus and E. coli, respectively, and the sublethal S. aureus and E. coli were reduced to 0.16 and 0.09 log cfu/ml. The increased cavitation effects make the simultaneous treatment (600 W, 63 °C, 5 min) the most effective approach in killing S. aureus and E. coli, causing 1.67 and 2.16 log reductions, respectively, and producing negligible sublethal bacteria. The simultaneous treatment was also able to improve some physical–chemical properties of milk; smaller particle size and whiter color were achieved. However, whey protein and stability indices of milk were slightly deteriorated by this approach.

Practical applications

In food processing fields, thermosonication can serve as an alternative processing technique to thermal pasteurization. Especially, the simultaneous treatment of ultrasound and heat showed best inactivation effect for viable and sublethal cells, while maintaining the overall milk quality in the meantime. The results of this research may be useful for the treatment of various bacterial contamination and give the guidance for milk processing.

The plant‐derived essential oil component eugenol (1.0% wt/vol), free or loaded into surfactant micelles constructed of sodium dodecyl sulfate (SDS; 1.0% wt/vol), 200 ppm free chlorine (hypochlorous acid [HOCl]; pH 7.0), and sterile distilled water were evaluated for their ability to reduce Salmonella Saintpaul and Escherichia coli O157:H7 on skin surface samples of Roma tomatoes. Samples were treated and then stored aerobically for up to 10 days. All samples were initially stored at 5 °C; one set of samples was shifted to 15 °C after 5 days of storage to simulate temperature abuse during postharvest handling. Encapsulated and free eugenol, HOCl, and empty SDS micelles reduced pathogens to nondetectable counts (detection limit: 0.5 log₁₀ cfu/cm²) during refrigerated storage (p ≥ .05). Conversely, during temperature abuse storage (15 °C), only free and micelle‐loaded eugenol consistently reduced pathogens to nondetection. Eugenol‐loaded micelles can be used to decontaminate harvested tomatoes from enteric bacterial pathogens.

Practical applications

Tomatoes may be consumed raw and have been repeatedly implicated in the occurrence of human foodborne disease. Washing of tomatoes with novel antimicrobial interventions that increase the dispersion of antimicrobials over the surface of the tomato should result in greater reduction of microbial foodborne pathogens through enhanced contact of antimicrobial with pathogen. Application of surfactant micelle‐entrapped eugenol onto tomato surfaces reduced Salmonella Saintpaul and Escherichia coli O157:H7 to nondetection during refrigerated (5 °C) and temperature abuse (15 °C) storage. Micelle‐loaded eugenol reduced numbers of aerobic bacteria, Enterobacteriaceae, and fungi to nondetection during temperature abuse storage.