A Mathematical Model for the Combination of Power Ultrasound and High-Pressure Processing in the Inactivation of Inoculated E. coli in Orange Juice

Response to Reviewer 1 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Can be improved

The manuscript has been revised to improve introduction, results and conclusion

Is the research design appropriate?

Can be improved

Are the methods adequately described?

Can be improved

Are the results clearly presented?

Can be improved

Are the conclusions supported by the results?

Can be improved

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1:  Line 111: E. coli and other bacterial name should be italic。Please check the whole manuscript, as well as figures and tables.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have checked, and all the microbial stains are now written in Italia.

Comments 2: Line 331: dot is missing after juice.

Response 2: Thank you for pointing this out. The manuscript has been emended as reviewer suggested.

Comments 3: Line 361: Is it Figure 2B?

Response 3: Thank you for pointing this out. Yes, it was an error and now the manuscript has been emended.

Comments 4: Table 2: why the value of table 2 doesn’t have the standard deviation like table 4

Response 4: Thank you for pointing this out. Actually 2 replications have been performed.

Comments 5: The resolution of Figure 3 is very low.

Response 5: I have uploaded a new picture

Comments 6: Table 2: The content of Table 6 is misplaced.

Response 6: The table has been replaced and emended

Comments 7: Figure 4 (left) is difficult to understand. I couldn’t connect the data of table 6 and Figure 4 (left). Is the symbol of 300 MPa and 400 MPa exchanged.

Response 7: Thank you for pointing this out. It was emended. Now should be clear.

Comments 8: Increase the discussion of the inactivate effect and the mathematical model for the combination of US and HPP treatment. 

Response 8: Thank you for the suggestion, the discussion has been improved. 

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

2. Questions for General Evaluation

Does the introduction provide sufficient background and include all relevant references?

Is the research design appropriate?

Are the methods adequately described?

Are the results clearly presented?

Are the conclusions supported by the results?

The effect of ultrasound application combined with high pressure processing on the inactivation of Escherichia coli inoculated in orange juice was studied by a mathematical model. The topic of this work is interesting. Some modifications are recommended.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1:  Microbial strains throughout the manuscript should be written in italic.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, We have checked, and all the microbial stains are now written in Italia.

Comments 2: HPP in line 42 should be defined. Lines 42-46: The stabilization mechanisms of HPP are not clearly introduced. Meanwhile, the factors affecting the stabilization effect of HPP are not stated.

Response 2: Thank you for pointing this out. The introduction has been emended as reviewer suggested:

L44-48: The main stabilization mechanisms involved in HPP are cell mebrane distruction, protein denaturation, DNA damage. The main factors affecting stabilization effect of HPP are the pressure level, duration of treatment, temperature, pH level, food composition, microbial resistance and food structure.

Comments 3: Lines 60-70: The examples are unnecessary. The authors should summarize the importance of combinedly using HPP and US.

Response 3: Thank you for pointing this out. The manuscript has been emended as suggested:

L64-69 The combined use of High-Pressure Processing (HPP) and ultrasound (US) significantly enhances microbial inactivation in food products. Increasing the amplitude of ultrasonic waves and applying higher pressure can improve the effectiveness of US [14]. When used together, HPP and US can exhibit both additive and synergistic effects, leading to greater reductions in pathogens [7, 15, 16,17]. This integration enhances food safety and preservation, making it a powerful approach in food processing.

Comments 4: Lines 71-73: This section is too simple and should be extended.

Response 4: Thank you for pointing this out. The manuscript has been emended as suggested:

L70-83 Mathematical modeling of the HPP and ultrasound processes is an area of significant interest, as it enables the detailed analysis and understanding of the dynamic behavior of various species within food products, including microorganisms, enzymes, and other bioactive compounds. These models are crucial for process control, optimization and prediction. In fact, mathematical models provide a framework for monitoring and controlling the conditions of HPP and US treatments. By simulating different scenarios, operators can identify optimal conditions that maximize microbial inactivation while preserving the quality of the food. Moreover, through modeling, it is possible to optimize parameters such as pressure, temperature, treatment time, and ultrasonic amplitude. This ensures that the processes are both effective and efficient, minimizing energy usage and maximizing product quality. Models can also predict the outcomes of various processing conditions on microbial inactivation and the stability of food components. This predictive capability is essential for designing processes that meet safety regulations and consumer expectations

Comments 5: Line 74: It has been shown... Check the language throughout the manuscript.

Response 5: Thank you for pointing this out. The manuscript has been emended as suggested:

L84-86: It has been demonstrated multiple times that when microorganisms are exposed to new nonthermal technologies, inactivation does not follow first-order kinetics. In this context, classical deterministic models based on first order kinetics are no longer applicable

Comments 6: The methods are described well.

Response 6: Thank you for pointing this out.

Comments 7: Table 2: Probe A and Probe B are not defined. The same for Probe C in the text.

Response 7: Thank you for pointing this out. The probes are defined in the text at L 128-129. Details were also included in  table 2.

Comments 8: Some figures are not very clear, such as Figs. 2-4.

Response 8: Thank you for pointing this out. I think the problem in this case depends on the submission process, in any case I will provide new images in case higher quality figures are needed.

Comments 9: At last, the authors should provide the suitable mathematical model.

Response 9: We thank the reviewer for the comment. The values of fixed the parameters set in the model, described in Section 3.5, have been included in the text in tabular form to provide all the necessary details of the mathematical model.

Comments 10: The conclusion should be shortened.

Response 10: Thank you for pointing this out. The conclusion has been shortened

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Can be improved

The manuscript has been revised as referee suggestion to improve all the section

Are all the cited references relevant to the research?

Can be improved

Is the research design appropriate?

Can be improved

Are the methods adequately described?

Can be improved

Are the results clearly presented?

Can be improved

Are the conclusions supported by the results?

Can be improved

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1:  Title, "non-thermal technologies", can the authors use the specific terms? Like "ultrasonic or/and high pressure processing".

Response 1: Thank you for pointing this out. The title of the manuscript has been emended as suggested. The new title proposed is: A mathematical model for the combination of power ultrasound and high-pressure processing in the inactivation of inoculated E. coli in orange juice

Comments 2: line 24, "2" should be superscripted. line 29, what is the abbrievation of ODE?

Response 3: Thank you for pointing this out. We have checked, and all the microbial stains are now written in Italia.

Comments 4: typeface should be consistent, line 296, in the table.

Response 4: Thank you for pointing this out. We have check it, and the manuscript was emended when required

Comments 5: Table 6, it should be improved. 

Response 5: Thank you for pointing this out. The table has been emended as suggested.

Comments 6: line 505-508 can be deleted.

Response 6: Thank you for pointing this out. The lines were deleted

Comments 7: reference list, some information are missing, such as pages or article code. Line 527, 532, and so on. The journal name can be abbreviated uniformly or not? Check line 544, 541, etc.  Please check them carefully and follow the requirements of journal strictly.

Response 7: Thank you for pointing this out. The reference list has been emended as suggested.

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

2. Questions for General Evaluation

Does the introduction provide sufficient background and include all relevant references?

Is the research design appropriate?

Are the methods adequately described?

Are the results clearly presented?

Are the conclusions supported by the results?

3. Point-by-point response to Comments and Suggestions for Authors

I have reviewed the manuscript foods-3262698 by Óscar Rodríguez and co-authors, “A mathematical model for the combination of non-thermal technologies in the inactivation of inoculated E. coli in orange juice.” The goal of the study was to examine the inactivation kinetics of Escherichia coli inoculated in orange juice in relation to power ultrasound (US), high-pressure processing (HPP), and the combination of these non-thermal technologies. A mathematical model was designed and implemented to predict these effects. The manuscript is interesting and contributes new knowledge regarding the inactivation kinetics of Escherichia coli inoculated in orange juice by ultra sound, high-pressure processing and combination of those processes. A few comments to improve the manuscript can be found below.

 Comments 1:  The abstract could be improved. The authors could add some numerical findings, the strain of E.coli, and process parameters to strengthen it.

Response 1: [Type your response here and mark your revisions in red] Thank you for pointing this out. The numerical finding is included, and the stain was specified.

Comments 2: Keywords: Instead of the abbreviation ODE the full name should be used.

Response 2: Thank you for pointing this out. It was emended

Comments 3: The introduction provides a good background on the subject. The objectives of the study are written clearly.

Response 3: Thank you for pointing this out.

Comments 4: 2.1. Bacteria stock culture and inoculum:

Comments 4a: Line 107. Please provide the collection where the strain of E. coli was acquired.

Response 4a: Sorry for this oversight, the provider has been added.

Comments 4b: It isn’t clear whether the juice was filtered or contained solid parts. Please clarify.

Response 4b: The juice did not contain solid particles.

Comments 4c:  The authors should provide the pH value or titratable acidity of the juice, as well as Brix or conductivity.

Response 4c: The pH and Brix are given as results in section 3.4.

Comments 4d:  Why did the authors choose the specific inoculum concentration? Was it based in some previously published source? Please elaborate.

Response 4d: It was because the treatment should be assuring at least 5 LOG reduction

Comments 4e: Is there a formal recommendation regarding the number of E.coli log10 cycles that should be inactivated by the applied process in orange juice?

Response 4e: Yes, there are formal recommendations regarding the inactivation of E. coli in orange juice. The U.S. Food and Drug Administration (FDA) typically recommends achieving a minimum of 5-log (i.e., 99.999%) inactivation of E. coli O157 for fruit juices, including orange juice. This level of inactivation is intended to ensure safety from pathogenic microorganisms.

Different regulatory agencies might have varying recommendations, so it's always good to check the specific guidelines relevant to your region or the specific process being used.

It was included in the text to discuss the results (L 444-447)

Comments 4f: Conclusion: The conclusions are consistent with the evidence and arguments presented.

Response 4f: Thank you for pointing this out.

Comments 5: Lines 488-489. The authors conclude that “The combined US+HPP treatment seems to act synergistically and results in no detectable colony-forming units per mL of juice” What was the detection limit of the survival count method? The authors should indicate it also in the diagrams.

Response 5: ND (not detected) means 0 CFU mL^-1. There were no colonies detected on the plate. The following formula for the calculation has been used:

 CFU/ml = (Number of colonies*dilution factor) / sample volume.

Comments 6: Have the tested doses an effect on the acceptability of the juice?

Response 6: Thank you for pointing this out. In this work, the acceptability of the juice was not studied. However, the activity was performed, and the results will be published in a following paper.

Comments 7: The references are not appropriately cited, from what I could assess. Please modify according to the mdpi’s instructions.

Response 7: Thank you for pointing this out. The reference has been modified according to the MDPI’s instructions.