High pressure carbon dioxide combined with high power ultrasound pasteurization of fresh cut carrot

• HPCD + HPU inactivated lactic acid bacteria, coliforms, yeasts and molds.
• HPCD + HPU induced 8 log reductions of E. coli spiked on fresh cut carrot.
• Texture and sensory analyses revealed significant changes of HPCD + HPU treated fresh cut carrot.

Nowadays, combination of innovative technologies aiming to obtain additive or synergistic effects on microbial inactivation of food products compared to the single processes is considered a field of great interest. In this context, the feasibility of a combined high pressure carbon dioxide and high power ultrasound (HPCD + HPU) treatment was tested for the pasteurization of fresh cut carrot.Inactivation kinetics of the natural microbial flora (mesophilic microorganisms, lactic acid bacteria, total coliforms and yeasts and molds) were determined at 12 MPa and 10 W delivered every 2 min of treatment as a function of temperature (22, 35 and 40 °C) and time (from 5 up to 30 min). Further Escherichia coli was spiked on fresh cut carrot and inactivation kinetics were obtained at 6, 8, 10 MPa and 10 W delivered every 2 min of treatment as a function of temperature (22 and 35 °C) and times (from 3 up to 30 min). The results of the inactivation kinetics were compared with those obtained with thermal, HPU and HPCD treatments.Additionally color, pH, acidity, texture and sensory analyses of the samples were performed to assess the quality of HPCD + HPU treated carrots in comparison with the fresh product.It was demonstrated that the combined treatment was not able to induce a greater reduction of the natural microbial flora at milder process conditions compared to HPCD. At 40 °C, 12 MPa, 15 min and 10 W still a residual load of mesophilic microorganisms was detected. On the contrary, the inactivation kinetics of E. coli showed a faster reduction: 3 min at 10 MPa, 35 °C and 10 W were enough to obtain 8 log reductions.Texture and sensory analyses revealed significant changes of HPCD + HPU treated samples with great reduction of firmness, friability and crispiness. The results showed the potentials and limits of the combined technology applied to fresh cut vegetables.

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