The Effect of Superficial Oregano Essential Oil Application on the Quality of Modified Atmosphere-Packed Pork Loin
Round 1
Reviewer 1 Report
The authors have done a good job. But I have some considerations:
· Authors are recommended to include values of the results obtained in the abstract.
· In materials and methods, the authors indicate that they incorporate 0.5% and 1% of oregano essential oil to the pork loin. Is this expressed in w/v, or in v/v? Subsequently, they indicate that they carry out a dilution in water, and that in this case they provide 1.5% w/v??. Therefore, what proportion of oregano essential oil is finally left in the pork loin? Why do they dilute? And why in water, knowing that essential oils are insoluble in water?.
· The authors indicate that the proportions of oregano essential oil added to the pork loin do not have antibacterial activity. But taking into account that this oil has 75% carvacrol, it would have to have it. In addition, other authors have incorporated between 0.2-0.8% presenting antimicrobial activity against K. pneumoniae, E. coli and MRSA (Man et al., 2019).
· What bacterial species appear in the count? Would oregano be effective against them?.
· Why does pH affect essential oils? Oregano is composed in your case by: carvacrol, ganma-terpinene, para-cymene, and linalool, which have a synergistic effect on each other, favoring the antimicrobial activity of the oil.
· In the determination of nutritional values, the values ​​of Carbohydrates, Sodium, Iron, and Salt must be incorporated, since they are part of the nutritional label.
· The authors incorporate 39 references, of which almost 40% are prior to 2018. It is recommended that the vast majority of citations be in the last 5 years.
· Man, A., Santacroce, L., Iacob, R., Mare, A., & Man, L. (2019). Antimicrobial activity of six essential oils against a group of human pathogens: A comparative study. Pathogens, 8(1), 15.
Author Response
Dear Reviewer, thank you very much for your detailed comments. Below we enclosed responses for each comment. In the manuscript, all changes were marked with red font.
Comment (C): The authors have done a good job. But I have some considerations:
Answer (A): Thank you. We corrected the manuscript according to your comments and replied point by point.
C: Authors are recommended to include values of the results obtained in the abstract.
A: The abstract was modified and more results were provided.
C: In materials and methods, the authors indicate that they incorporate 0.5% and 1% of oregano essential oil into the pork loin. Is this expressed in w/v, or in v/v? Subsequently, they indicate that they carry out a dilution in water and that in this case, they provide 1.5% w/v??. Therefore, what proportion of oregano essential oil is finally left in the pork loin? Why do they dilute? And why in water, knowing that essential oils are insoluble in water?
- Thank you for the comment. We would like to explain that in the study oregano essential oil in the concentration of 0.5% and 1.0% (v/v) were used. The oregano essential oil in concentrations of 0.5% and 1.0% (v/v) was used. These concentrations were used based on our previous studies (data not published), in which higher concentrations produced pork with too intensive a herbal aroma. The solutions were prepared by mixing 0.5 ml of the oregano EO with 99.5 ml of distilled water to obtain a concentration of 0.5% and 1.0 ml of the EO with 99.0 ml of distilled water to obtain a concentration of 1.0%. Although essential oils are not soluble in the water we used it as a medium, because ethanol solution produced a meat surface discolouration as noted in our preliminary studies. Obtained solutions were spread over the surface of each meat piece using disposable atomizers in the amount of 1.5% in respect of the weight of each pork loin slice. Each pork loin slice was weighted to calculate the amount of the solution needed to be spread. The aqueous solution of the oregano EO was shaken well before its application on the pork loin slice surface. Using the above-described solutions and amount spread on the surface the actual concentration of the oregano essential oil on the pork loin surface was 0.0075% and 0.015% when using 0.5% and 1.0% of the oregano EO solutions, respectively.
The description was provided in the Material and Methods section.
C: The authors indicate that the proportions of oregano essential oil added to the pork loin do not have antibacterial activity. But taking into account that this oil has 75% carvacrol, it would have to have it. In addition, other authors have incorporated between 0.2-0.8% presenting antimicrobial activity against K. pneumoniae, E. coli and MRSA (Man et al., 2019).
A: Thank you for the comment. The lack of the antimicrobial effect noted in the present study was discussed in the newly introduced paragraph in the Discussion section: “Oregano essential oil is known for its high efficiency in bacterial growth inhibition. In the study of Man et al. (2019), its inhibitory effect on the most common pathogenic bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa) was reported when used in the form of micelle suspensions in an in vitro studies. In the present study, the oregano essential oil effectiveness was tested in the raw meat environment stored in the MAP and a slight inhibitory effect of the oregano oil was noted. The lack of the strong antimicrobial effect of the oregano essential oil on TVC noted in the present study might result from a low concentration obtained in the pork surface and MAP composition used in the study. Skandamis and Nychas (2002) noted that the inhibitory potential of essential oregano oil depended on the method the meat was packed and stored. It was the lowest when meat samples were stored in the air and increased in the following order: vacuum < 100% CO2 < MAP 40% CO2, 30% N2, 30% O2. In the present study, MAP contained as much as 70% of oxygen. As pointed out by Zhang and Piao (2023) there are some factors which limit the application of essential oils in meat and meat products, including their sensitivity to light and oxygen. Other limiting factors are interactions of essential oils with lipophilic components of the meat matrix (fats and protein), high volatility, and low solubility in the aqueous phase (Zhang and Piao, 2023; Snoussi et al., 2022). Therefore, it might be concluded that in the atmosphere with such a high oxygen proportion as used in the study, the oregano EO partially lost its activity, which resulted in a slight antimicrobial effect and failure in preventing meat surface discolouration during storage.
C: What bacterial species appear in the count? Would oregano be effective against them?
A: The present study was aimed at studying the possibility of essential oil in preventing pork discolouration and therefore only basic microbiological analysis was conducted. We examined only total viable counts without qualitative analysis.
C: Why does pH affect essential oils? Oregano is composed in your case by: carvacrol, ganma-terpinene, para-cymene, and linalool, which have a synergistic effect on each other, favoring the antimicrobial activity of the oil.
A: In the present study we noted that the pH value of meat was not affected by oregano oil addition (Table 4). However, time affected pH significantly. The effect of pH on EO was not studied in the present paper.
C: In the determination of nutritional values, the values ​​of Carbohydrates, Sodium, Iron, and Salt must be incorporated, since they are part of the nutritional label.
A: According to the information provided by the meat processing plant which orders monitoring of nutritional value in an accredited laboratory (Eurofins Polska Sp. z.o.o., Malbork, Poland) the meat contains below 0.5% carbohydrates, fibre <0.2%, salt <0.25% and sodium less than 0.1 g in 100 g. The information was provided in the text.
C: The authors incorporate 39 references, of which almost 40% are prior to 2018. It is recommended that the vast majority of citations be in the last 5 years.
A: We have added the latest publications on the subject discussed in the article. Articles older than 5 years that we quoted are important to us because they contain important information from the point of view of the methodology used and the results discussed.
Reviewer 2 Report
This manuscript reports on the effect of direct surface application of oregano essential oil (EO) on the quality of fresh pork loin with major emphasis on color of that meat. The authors hypothesized that the application of oregano EO will preserve color of the meat for up to 15 days of storage. The major findings are that the concentrations of oregano EO (0.5% and 1.0%), selected on the basis results of sensory tests, were too low to protect meat color and improve the microbial quality of the meat. The findings of this research confirm the findings of published reports that a major challenge in use of EOs in foods, including meats, is concomitantly maintaining desirably sensory characteristics of the food at EOs levels that are effective in improving microbial quality. However, based on the results of the present study, the oregano EO has good potential for use in producing a new pork product with an acceptable herbal aroma and taste. Generally, the manuscript is well written with clear objectives, and well-designed experiments for testing the authors’ hypothesis. The results are fully discussed with reference to pertinent published reports, and the conclusions are supported by the research findings. In spite of these attributes, the manuscript’s contribution to body of scientific knowledge in the area of application of EOs in meats less than substantial. Also, the microbiology section of the methods section lack adequate details for other researchers to repeat the experiment. Please see the following comments and suggestions for improving the manuscript.
Lines 12 - 13: Rewrite this sentence to improve its syntax. This reviewer's suggestion is to place "In the present study,.." at the beginning of the sentence, or use a clearer sentence construction.
Line 26: "...whereas sensory quality and cooking losses after thermal treatment". This part of the sentence is unclear. It is likely that a word is missing. Please correct this error.
Line 29: "..with on modifications in water holding capacity of the meat". Correct the error in this part of the sentence, which is unclear.
Line 63: Insert a comma (,) between "vacuum" and "Showed" to improve the syntax of the sentence.
Line 88. State the storage temperature related to this 14-day shelf-life.
Line 89: Change "put" to "puts" for correct subject and verb agreement.
Lines 95 - 96. "…concentrations which are able to inhibit bacterial growth are too high from a safety perspective". The sentence conveys to the reader that the antibacterial concentrations of oregano used in that study were unsafe. Is this the information that the authors are presenting in the present introduction? Based on the remainder of the sentence, it seems that a "quality perspective" makes more sense.
Line 113. "bathes"? or "batches". Please make the appropriate correction.
Line 191. Place a comma (,) between "packages" and "samples" for proper sentence construction.
Line 201. Place a comma (,) after "assessment".
Lines 216 - 220. Provide more details on microbiological analysis so that other researchers could accurately repeat the methods. For example, state the following information: i) type and amount of sterile diluent used for homogenizing the 10-g pork sample, ii) the type of diluent used for making dilutions of the meat homogenate, iii) actual type of Petrifilm agar used, and iv) data handling ie were the microbial counts converted to Log CFU/g?
Line 239: Change "was' to "is" to be consistent with the tense of the verb. This change would give ". The influence of EO addition and time on pork color is shown in Table 1"
Line 322. Delete the period (.) between "(p < 0.001)" and "whereas".
The quality of the English language is good.
Author Response
Dear Reviewer, thank you very much for your detailed comments. Below we enclosed responses for each comment. In the manuscript, all changes were marked with a red font.
Comment (C): This manuscript reports on the effect of direct surface application of oregano essential oil (EO) on the quality of fresh pork loin with major emphasis on color of that meat. The authors hypothesized that the application of oregano EO will preserve color of the meat for up to 15 days of storage. The major findings are that the concentrations of oregano EO (0.5% and 1.0%), selected on the basis results of sensory tests, were too low to protect meat color and improve the microbial quality of the meat. The findings of this research confirm the findings of published reports that a major challenge in use of EOs in foods, including meats, is concomitantly maintaining desirably sensory characteristics of the food at EOs levels that are effective in improving microbial quality. However, based on the results of the present study, the oregano EO has good potential for use in producing a new pork product with an acceptable herbal aroma and taste. Generally, the manuscript is well written with clear objectives, and well-designed experiments for testing the authors’ hypothesis. The results are fully discussed with reference to pertinent published reports, and the conclusions are supported by the research findings. In spite of these attributes, the manuscript’s contribution to body of scientific knowledge in the area of application of EOs in meats less than substantial. Also, the microbiology section of the methods section lack adequate details for other researchers to repeat the experiment. Please see the following comments and suggestions for improving the manuscript.
Answer (A): Thank you. We corrected the manuscript according to your comments and replied point by point.
C: Lines 12 - 13: Rewrite this sentence to improve its syntax. This reviewer's suggestion is to place "In the present study,.." at the beginning of the sentence, or use a clearer sentence construction.
A: Corrected
C: Line 26: "...whereas sensory quality and cooking losses after thermal treatment". This part of the sentence is unclear. It is likely that a word is missing. Please correct this error.
A: Corrected. The sentence was rewritten.
C: Line 29: "..with on modifications in water holding capacity of the meat". Correct the error in this part of the sentence, which is unclear.
A: Corrected. The sentence was rewritten.
C: Line 63: Insert a comma (,) between "vacuum" and "Showed" to improve the syntax of the sentence.
A: Corrected
C: Line 88. State the storage temperature related to this 14-day shelf-life.
A: The shelf life of pork meat (manufacturer's declaration) was determined on the basis of the regulation specifying the detailed conditions required for the production, storage and transport of meat and meat products not subjected to heat treatment (Journal of Laws 2002.241.2086) and by performing storage tests in refrigerated conditions 4 °C. 14-day storage time is recommended for 4°C refrigerated conditions. The information about temperature was added to the text.
C: Line 89: Change "put" to "puts" for correct subject and verb agreement.
A: corrected
C: Lines 95 - 96. "…concentrations which are able to inhibit bacterial growth are too high from a safety perspective". The sentence conveys to the reader that the antibacterial concentrations of oregano used in that study were unsafe. Is this the information that the authors are presenting in the present introduction? Based on the remainder of the sentence, it seems that a "quality perspective" makes more sense.
A: Thank you for the comment; we deleted the expression “not safe” from the sentence.
C: Line 113. "bathes"? or "batches". Please make the appropriate correction.
A: corrected
C: Line 191. Place a comma (,) between "packages" and "samples" for proper sentence construction.
A: corrected
C: Line 201. Place a comma (,) after "assessment".
A: corrected
C: Lines 216 - 220. Provide more details on microbiological analysis so that other researchers could accurately repeat the methods. For example, state the following information: i) type and amount of sterile diluent used for homogenizing the 10-g pork sample, ii) the type of diluent used for making dilutions of the meat homogenate, iii) actual type of Petrifilm agar used, and iv) data handling ie were the microbial counts converted to Log CFU/g?
A: The above-mentioned information was provided.
C: Line 239: Change "was' to "is" to be consistent with the tense of the verb. This change would give ". The influence of EO addition and time on pork color is shown in Table 1"
A: corrected
C: Line 322. Delete the period (.) between "(p < 0.001)" and "whereas".
A: corrected
Authors would like to thank the Reviewer for pointing out editorial errors. All changes have been made in the text.
Reviewer 3 Report
The article presents a valuable study on the application of oregano essential oil on the surface of pork loin packed in modified atmosphere. In addition, no other studies have already investigated the effect of this EO on pork loin colour parameters. Overall, the manuscript is well organized and written. However, I do see some inaccuracies that should be improved:
Introduction section
In all the manuscript check English grammar, please.
Line 41-44, 58-62, 89-92, 94-98, - These periods are too long for a research paper. It should be appropriate to reformulate them, please.
Line 110 – Remove the bracket before “a crossbred”, please.
Line 127 – Add final bracket “(Traysealer A6 SEALPAC (Sealpac, Oldenburg, Germany)”, please.
Line 181, 322– Remove full stop after, respectively, “5 min”, “(p < 0.001)”.
Results section
Line 238- 252 - This paragraph is very confusing, there is no correspondence between title and the text. The title is “The effect of EO on the MAP-packed pork colour”, but in the text the influence of time is also reported. Check it, please.
Figure 1: Check the expression result on y-axis “log CFU/g” and the statistical letter in the graph.
Tables 1 to 5: It should be appropriate to add the same decimals in all the table.
Discussion section
Line 364- 367 – It should be appropriate to add some discussion of these finding. What could be the reasons of L* and a* colour trend? Check it, please.
Line 372- 373- Please, write 2 in subscript form “70% O2 / 372 25% CO2 / 5% N2”.
\
Author Response
Dear Reviewer, thank you very much for your detailed comments. Below we enclosed responses for each comment. In the manuscript, all changes were marked with red font.
Comment (C):The article presents a valuable study on the application of oregano essential oil on the surface of pork loin packed in modified atmosphere. In addition, no other studies have already investigated the effect of this EO on pork loin colour parameters. Overall, the manuscript is well organized and written. However, I do see some inaccuracies that should be improved:
Answer (A): Thank you. We corrected the manuscript according to your comments and replied point by point.
C: Introduction section. In all the manuscript check English grammar, please.
A: Thank you. English was revised.
C: Line 41-44, 58-62, 89-92, 94-98, - These periods are too long for a research paper. It should be appropriate to reformulate them, please.
A: The sentences were reformulated to make them shorter and easily understandable.
C: Line 110 – Remove the bracket before “a crossbred”, please.
A: corrected
C: Line 127 – Add final bracket “(Traysealer A6 SEALPAC (Sealpac, Oldenburg, Germany)”, please.
A: corrected
C: Line 181, 322– Remove full stop after, respectively, “5 min”, “(p < 0.001)”.
A: corrected
Results section
C: Line 238- 252 - This paragraph is very confusing, there is no correspondence between title and the text. The title is “The effect of EO on the MAP-packed pork colour”, but in the text the influence of time is also reported. Check it, please.
A: Thank you for the comment. It was corrected for “3.2. The effect of EO and storage time on the MAP-packed pork colour”
C: Figure 1: Check the expression result on y-axis “log CFU/g” and the statistical letter in the graph.
A: The title of y-axis was modified into log10 CFU/g. On the figure the indication of the lack of significant differences between treatments (NS) was added.
C: Tables 1 to 5: It should be appropriate to add the same decimals in all the table.
A: Thank you. In Table 4, a second decimal number to values was added. In the Table 5 we decided to keep only one decimal number due to the fact that sensory assessment was conducted in natural numbers (integers), so the decimals are resulted of the mean value calculations and there is no need to indicate 2 decimal numbers.
Discussion section
C: Line 364- 367 – It should be appropriate to add some discussion of these finding. What could be the reasons of L* and a* colour trend? Check it, please.
A: An explanation has been added, “This is related to protein denaturation, which induces an increase in the L* parameter in meat (Bassey 2022), while oxidation and metmyoglobin formation cause a decrease in a* (Mancini and Ramanathan, 2020) and consequently an increase in b* values (Luong et al., 2020).” A detailed discussion of the reasons for changes in the colour descriptors L* and a* are discussed in the lines 392 – 409.
C: Line 372- 373- Please, write 2 in subscript form “70% O2 / 372 25% CO2 / 5% N2”.
A: Corrected
Authors would like to thank the Reviewer for pointing out editorial errors. All changes have been made in the text.
Round 2
Reviewer 2 Report
The authors have satisfactorily addresses this reviewer's suggestions and comments. I have no further suggestions for revision of the manuscript.
