Application of Gamma Irradiation Treatment on the Physicochemical and Microbiological Quality of an Artisanal Hard Cheese

Round 1

Reviewer 1 Report

The article focuses on the application of irradiation on the quality of artisanal hard cheese. This study covers different physicochemical, sensorial and microbiological aspects, and provides a complete overview of the quality of the cheese following irradiation treatment

I recommend this article for publication, as outcomes are of interest and results are appropriately presented and relevant for the field.

Specific comment:
I would suggest reformulating the title as follow: Effects of Gamma irradiation treatment on the physicochemical, sensorial and microbiological quality of an artisanal hard cheese.
In the methodology, the section numbers need to be updated (2.6 is after 2.8)
For statistical analysis, it would be more appropriate to perform factorial analysis (size sample*irradiation sample). Indeed, later in the results sections, you mention the impact of the size sample on some properties. 
Table 1, precise in the note under the table that values correspond to the average of 250 and 500g samples.
Table 2 and 3, Since there is a difference between samples for 250 and 500g for texture properties, I recommend separating colour and texture properties. The second table with texture parameters would reflect factorial analysis size sample*irradiation treatment. Lastly, as results will probably show a factorial effect, then it is not appropriate to show the average values of 250 and 500g for textural parameters.
Similarly, for Figures 2 and 3, they can be combined to represent the factorial effect. These figures 2 and 3 are only valid if the statistical effect is a simple effect.
3.5 Costs evaluation: It would be interesting to compare this technology in terms of energy consumption, with other thermal and non-thermal technologies, showing both advantages and disadvantages.

Author Response

Comment: I would suggest reformulating the title as follow: Effects of Gamma irradiation treatment on the physicochemical, sensorial and microbiological quality of an artisanal hard cheese.

Response: The title was reformulated.

Comment: In the methodology, the section numbers need to be updated (2.6 is after 2.8)

Response: Section numbers were updated.

Comment: For statistical analysis, it would be more appropriate to perform factorial analysis (size sample*irradiation sample). Indeed, later in the results sections, you mention the impact of the size sample on some properties. 

Response: Table 2 and 3 were restructured to show the factorial analysis
Comment: Table 1, precise in the note under the table that values correspond to the average of 250 and 500g samples.

Response: The note was added.
Comment: Table 2 and 3, Since there is a difference between samples for 250 and 500g for texture properties, I recommend separating colour and texture properties. The second table with texture parameters would reflect factorial analysis size sample*irradiation treatment. Lastly, as results will probably show a factorial effect, then it is not appropriate to show the average values of 250 and 500g for textural parameters.

Response: Table 2 and 3 were restructured to show the factorial analysis.

Comment: 3.5 Costs evaluation: It would be interesting to compare this technology in terms of energy consumption, with other thermal and non-thermal technologies, showing both advantages and disadvantages.

Response: The study did not focus on energy consumption but rather the overall cost charged by companies that perform the treatment. It would be interesting to find out. Unfortunately we are also not able to retrieve that information anymore.

Reviewer 2 Report

This manuscript was discussed the effect of gamma irradiation treatment on the quality of artisanal hard cheese. The application on bacteriostatic activity seems positive on cheese preservation, but there are lots of questions should be slove and improved.

1.The english writting ability should be improve, there are lots of grammar error and  misspelling in this manuscript.

2.the author define small scale, but in the experiment desigh 250 g and 500 g were the commercial size for using?

3.In the introduction, the author should add more recent informations on the gamma irradiation on the bacteriostatic properties of foods.

4.in line 91-93, line 91 positive? line 93 negative?

5.in section 2.2, the time treatment on chesse should be mention.

6.In table 4, what are 278 and 369.

7.in line 373-374, sensory analysis did not in the method should be deleted.

8.In 3.4, how about the original status of bacterial count?

9.in line 405, ,what is the recommended limit?

10.different size should be have different irradation time and area, the author should be indicate the time and obvious radiation area in the revised manuscript.

11.the photo of cheese before and after treated with gamma irradiation should be add in the manuscript.

12.there are no data on the Listeria bacteria, and the reason to analysis this bacteria?

13.In section 3.5, how about the price of this irradiation-producing machine? and the author should be consider the cost of machine in the section.

14.In section 2.6, the meaning of equation Yijk?

15.in section 2.8, using 3M bacterial method for ACC, E. Coli and Listeria were the suitable method?

16.the author should be explain clear about the change of cheese odor before and after? 

17. the author discussed the bactericide effect by gamma irradiation should be  consider the gram postive, gram negative bacteria. And how about the problem of yeasts and moulds?

Author Response

Comment: The english writting ability should be improve, there are lots of grammar error and  misspelling in this manuscript.

Response: The article was read and improved where needed by a native English speaker.

Comment: The author define small scale, but in the experiment design 250 g and 500 g were the commercial size for using?

Response: 250 and 500 g samples were used for this study since they are the most popular retail sizes found in local stores.

Comment: In the introduction, the author should add more recent informations on the gamma irradiation on the bacteriostatic properties of foods.

Response: Information on gamma radiation in dairy and dairy product was included in the last paragraph of the introduction.

Comment: In line 91-93, line 91 positive? line 93 negative?

Response: The sentence was restructured

Comment: In section 2.2, the time treatment on cheese should be mention.

Response: The dose rate used was 1 kGy/h and it’s mentioned in section 2.2.

Comment: In table 4, what are 278 and 369.

Response: These are the samples used for the SmartNose analysis. This was clarified in the text (section 3.3) as well.

Comment: In line 373-374, sensory analysis did not in the method should be deleted.

Response: The sensory analysis was mentioned as a recommendation for future studies or gap that needs attention.

Comment: In 3.4, how about the original status of bacterial count?

Response: Figure 2 shows the microbiological status of the samples before treatment.

Comment: In line 405, what is the recommended limit?

Response: The recommended limits are written in section 3.4 (second line)

Comment: Different size should be have different irradiation time and area, the author should be indicate the time and obvious radiation area in the revised manuscript.

Response: The dose rate used was 1 kGy/h and it’s mentioned in section 2.2, 250 g and 500 g samples were irradiated as mentioned in section 2.2

Comment: The photo of cheese before and after treated with gamma irradiation should be add in the manuscript.

Response: Unfortunately we are not able to retrieve the photos of the samples. However, no visual differences on the samples before and after the treatment were noted.

Comment: There are no data on the Listeria bacteria, and the reason to analysis this bacteria?

Response: Listeria results are mentioned in the methodology, we used a rapid test to just identify positive samples and they were 4 out of 24 which is16 %. Those 4 samples tested negative after the treatment as mentioned in the results section 3.4.  Listeria was analysed because it is pathogenic microorganism of interest and often an issue in Southern Africa, where the research took place.

Comment: In section 3.5, how about the price of this irradiation-producing machine? and the author should be consider the cost of machine in the section.

Response: The point raised is interesting. However, at the time of the research, an ordinary small scale producer could not afford the equipment. Small-scale producer would have to look out for service providers. This is what is also normally done for other foods.

Comment: In section 2.6, the meaning of equation Yijk?

Response:  This is the model used for the analysis of variance

Comment: In section 2.8, using 3M bacterial method for ACC, E. Coli and Listeria were the suitable method?

Response: Yes

Comment: The author should be explain clear about the change of cheese odor before and after? 

Response: The changes are explained in section 3.3

Comment: The author discussed the bactericide effect by gamma irradiation should be consider the gram postive, gram negative bacteria. And how about the problem of yeasts and moulds?

Response: The samples did not have any yeasts and moulds, however this can still be included in future researches.

Reviewer 3 Report

The paper discusses an interesting topic with possible practical applications. Some remarks aiming the improvement of the manuscript submitted:

• The Authors outline the advantages of irradiation in the Introduction without discussing the drawbacks of this method, these latter including alteration of sensory quality and limitations of applications. Also, they should mention that EU legislation is rather restrictive in permitting food irradiation (the Authors and the product examined is from the EU!).
• It is known that foods with high fat contents, such as cheeses, develop off-odours and tastes due to the acceleration of rancidity, this latter being also a source of undesired free radicals. How did the Authors take into account this when designing their experiments?
• Terpenes, as important aroma compounds, were apparently not affected by irradiation- this should be mentioned as a positive aspect of the results obtained.
• Safrole is strongly carcinogenic- this should be mentioned in the paper as a possible problem.
• Why are figures for Listeria monocytogenes not reported? It would be an important aspect to control these pathogens.

Author Response

Comment: The Authors outline the advantages of irradiation in the Introduction without discussing the drawbacks of this method, these latter including alteration of sensory quality and limitations of applications.

Response: Drawbacks of the irradiation treatment have been included in the Introduction.

Comment: Also, they should mention that EU legislation is rather restrictive in permitting food irradiation (the Authors and the product examined is from the EU!).

Response: EU legislation was used as a reference since they are no well-established regulations from the country (South Africa) were the study was done. The product was also manufactured in South Africa.

Comment: It is known that foods with high fat contents, such as cheeses, develop off-odours and tastes due to the acceleration of rancidity, this latter being also a source of undesired free radicals. How did the Authors take into account this when designing their experiments?

Response: We used a low fat cheese type and also irradiated the samples at a dosage which is less than 5 kGy, which was noted to have less adverse effects on cheese.

Comment: Terpenes, as important aroma compounds, were apparently not affected by irradiation- this should be mentioned as a positive aspect of the results obtained.

Response: Terpenes were mentioned as suggested

Comment: Safrole is strongly carcinogenic- this should be mentioned in the paper as a possible problem.

Response: The possible problem was mentioned as recommended

Comment: Why are figures for Listeria monocytogenes not reported? It would be an important aspect to control these pathogens.

Response: Listeria results are mentioned in the methodology, we used a rapid test to just identify positive samples and they were 4 out of 24 which is16 %. Those 4 samples tested negative after the treatment as mentioned in the results section 3.4.

Reviewer 4 Report

Comments to the Author

In this study, the effect of gamma irradiation on the compositional, textural, colour, odour, and microbiological quality of an artisanal hard cheese was examined. These findings provide a scientific basis for the industrialization of the preservation of hard cheese. It reads as interesting research, but some elaboration and amendment would be useful.

This manuscript needs minor revision in order to become acceptable as Research article at applied sciences

Title:

The authors should remove either γ or gamma from the title.

Abstract:

Some values should be added to the abstract to be more informative, and the first statement (Irradiation treatment can be an effective way of reducing the incidence of food-borne pathogens on cheese for small-scale producer) line 15 and 16 should be removed from the abstract.

Introduction:

The introduction is relevant. However, information about the gamma radiation in dairy and dairy product are missing.

Materials and methods:

Overall, this section is well written.

Section 2.1: this section described the processing of cheese. Thus, the subtitle should be change, also, reference is missing.

Results and discussion:

Results and discussion in a very informative way.

• The author should change Before and after in the whole text and tables too; Before to 0.0 kGy, After to 5.0 kGy.
• Only table 3 shows the results of different cheese weights while the other tables are not. Authors should explain the responses or add the results
• why the data in table 3 does not show the values of the control sample
• the PCA fig 1 is not clear.

Author Response

Comment: The authors should remove either γ or gamma from the title.

Response: γ was removed from the title.

Comment: Some values should be added to the abstract to be more informative.

Response: Value for cheese composition and microbial counts were added.

Comment: The first statement (Irradiation treatment can be an effective way of reducing the incidence of food-borne pathogens on cheese for small-scale producer) line 15 and 16 should be removed from the abstract.

Response: The first statement was removed.

Comment: The introduction is relevant. However, information about the gamma radiation in dairy and dairy product are missing.

Response: Information on gamma radiation in dairy and dairy product was included in the last paragraph of the introduction. 

Comment: Materials and methods: Overall, this section is well written.

Section 2.1: this section described the processing of cheese. Thus, the subtitle should be change, also, reference is missing.

Response: The title for section 2.1 was changed and a reference added.

Comment: Results and discussion: The author should change Before and after in the whole text and tables to; Before to 0.0 kGy, After to 5.0 kGy.

Response: Before and after in the whole text and tables was changed to 0.0 kGy and 5.0 kGy, respectively.

Comment: Only table 3 shows the results of different cheese weights while the other tables are not. Authors should explain the responses or add the results

Response: No significant differences were noted between the 250 g and 500 g for composition and colour properties, therefore the tables are not included.

Comment: why the data in table 3 does not show the values of the control sample

Response: Samples before the irradiation treatment or at 0.0 kGy are the controls and the results are in Table 2.

Comment: The PCA fig 1 is not clear.

Response: The figure was enlarged. However, unfortunately the figure is generated by the software and not editable.

Round 2

Reviewer 2 Report

The author had corrected the manuscript according to my comments, but I still have some suggestionss on this revised manuscript, as follows:

1.The title should be change ", because the author did not mention about the data of sensory evoluation.

2.I suggest the title sould be change into "Application of Gamma irradiation treatment on the physical quality of an artisanal hard cheese".

3.I suggest the author should add more paragraph on the section of introduction, such as recent study of cold sterilization on the preservation of cheese or a brief introduction on the artisanal hard cheese.

4.I suggestion the conclusion should be re-written, because of in present description, the reader might confused about the sentence, "However, the cheese must be processed following good manufacturing practices and be carefully handled before and after irradiation. More studies need to be done on consumer perceptions and acceptability regarding irradiated cheese, and efforts should be made to standardize the process parameters."

Author Response

Dear Editor/Reviewer,

We are grateful to the reviewers and the editor for reviewing our manuscript. The comments were very useful and we believe we have addressed all of them as recommended. All revisions on the manuscript have been marked up using the “Track Changes”. Please find a detailed list of responses to the reviewer’s comments below:

Responses to comments

REVIEWER 3

Comment: The title should be changed ", because the author did not mention about the data of sensory evaluation.

Response: The title was changed.

Comment: I suggest the title should be change into "Application of Gamma irradiation treatment on the physical quality of an artisanal hard cheese".

Response: The title was changed into “Application of Gamma irradiation treatment on the physicochemical and microbiological quality of an artisanal hard cheese”. We believe both physical and chemical quality were addressed, besides microbiological characteristics.

Comment: I suggest the author should add more paragraph on the section of introduction, such as recent study of cold sterilization on the preservation of cheese or a brief introduction on the artisanal hard cheese.

Response: A brief introduction on artisanal hard cheeses was added. However, the study focused on ionizing radiation and other different inexpensive non-thermal treatments for food preservation such as the ultraviolet and X-rays are discussed in the first paragraph of the Introduction, not sure how we can factor in cold sterilization in this study.

Comment: I suggestion the conclusion should be re-written, because of in present description, the reader might confused about the sentence, "However, the cheese must be processed following good manufacturing practices and be carefully handled before and after irradiation. More studies need to be done on consumer perceptions and acceptability regarding irradiated cheese, and efforts should be made to standardize the process parameters."

Response: The conclusion was rephrased to address the concern.

Author Response File: Author Response.docx