Oxidative Stability Analysis of Selected Oils from Unconventional Raw Materials Using Rancimat Apparatus

Round 1

Reviewer 1 Report

The MS is nicely written and the findings are very well presented in a good manner. Congratulations.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thank you for your time and favourable review.
Below is the answer to your comment.

Comment 1:

"The source of procurement may be mentioned"

Answer:

Unfortunately, the manufacturer did not agree to include the company's name. Of course, that would enrich the manuscript. There is information that the oils were obtained directly from the manufacturer after extrusion.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript is well written however there is still room for improvement, especially in the conclusion part. Simplify the conclusion. Only highlight the outcome of the study. Page 3: indicate the reference. Page 5: adjust the table. There are about 16 references that are outdated:  11-15, 19, 21, 27, 31, 35-36, 40, 42, 45, 54, 62, 65.

Author Response

Dear Reviewer,

Thank you for your time and favourable review.
Below are the answers to your comments.

General comment: The manuscript is well written however there is still room for improvement, especially in the conclusion part.

Comment 1: Simplify the conclusion. Only highlight the outcome of the study.

Answer:

Old version:

Oils from unconventional raw materials such as herb or vegetable seeds interested researchers and consumers due to their unique chemical composition. Vegetable oils, especially the unrefined ones, are rich in bioactive compounds, tocopherols, sterols, phenolic compounds and carotenoids. In addition, the high content of unsaturated fatty acids makes these oils a source of valuable fat and a high nutritional value. However, these oils can undergo oxidative changes quickly due to the high proportion of polyunsaturated fatty acids and unacceptable processing or storage conditions. This research aimed to investigate the oxidative stability of the selected herb and vegetable seed oils (basil, fenugreek, coriander, tomato, watercress, parsley and dill) using the Rancimat apparatus and oxidation kinetics parameters. Calculated oxidation kinetics parameters correlated with varying strength with individual oil quality discriminants. The oxidation rate constant was strongly correlated with the induction time of oils, the colour of the oil and the calculated COX coefficient. On the other hand, the activation energy of the oxidation reaction correlated strongly with the colour of the oil and the content of carotenoid dyes. The rate of the oxidation reaction does not correlate with the energy needed to start the reaction.

New version:

Oils from unconventional raw materials such as herb or vegetable seeds are characterised by intense colour, specific taste and smell but also are distinguished by unique chemical composition. Investigated selected oils (basil, fenugreek, coriander, tomato, watercress, parsley and dill) were characterised by low free fatty acids content and a high degree of oxidation. The specific colour of oils results from the varied content of carotenoid and chlorophyll pigments. Consuming cold-pressed oils can positively affect human health, as evidenced by the designated nutritional quality indicators. These oils show a low pro-atherosclerotic and pro-thrombotic potential. Cold-pressed oils vary in their oxidation stability. One of the factors influencing the stability of oils is undoubtedly the composition of fatty acids. Oils' induction time reduced with increasing temperature of the Rancimat analysis, which confirms that the temperature significantly influences the course of the oxidation reaction. The determined reaction rate constants (k) increased with increasing temperature oxidation in the Rancimat apparatus. Additionally, oils rich in polyene fatty acids had higher k values ​​than oils containing more saturated and monounsaturated fatty acids. Calculated oxidation kinetics parameters correlated with varying strength with individual oil quality discriminants. The oxidation rate constant was strongly correlated with the induction time of oils, the colour of the oil and the calculated COX coefficient. On the other hand, the activation energy of the oxidation reaction correlated strongly with the oil's colour and the carotenoid pigments' content. The oxidation reaction rate does not correlate with the energy needed to start the reaction.

Comment 2: Page 3: indicate the reference.

Answer: The reference has been added to the text in the" Fatty acid composition analysis" section.

"… A TRACE TM 1300 gas chromatograph (Thermo Scientific, Waltham, MA, USA) equipped with an FID detector and a 60 m long, 0.22 mm BPX 70 capillary column with a layer thickness of 0.25 µm was used to determine the fatty acid composition. Determination of esterified fatty acids in the tested oils was performed according to the AOCS Official Method 966.06 [11], with minor modifications. The carrier gas was helium with a flow rate of 40 ml per minute; at a separation of 500:1, …"

Comment 3: Page 5: adjust the table.

Answer: the table has been adjusted.

Comment 4: There are about 16 references that are outdated:  11-15, 19, 21, 27, 31, 35-36, 40, 42, 45, 54, 62, 65.

Answer: Yes, I agree with this comment. Nevertheless, these are very important for publications and necessary to properly discuss the obtained results.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript titled “Oxidative stability analysis of selected oils from unconventional raw materials using Rancimat apparatus” is an original research article that investigated oxidative stability of some selected oils using. The approach and results will interest readers and could provide good input for the foods industry. However, some correction of English and incorporating the suggested corrections would improve the manuscript’s readability and help in meeting the journal publication standards.

Graphical abstract:

 

-          NA

 

Title:

 

-          The title is appropriate and explains the full scope of the study

 

Highlights:

 

-          NA

 

Abstract:

-          Abstract is within the word limits. However, it is talking more about the statistics. Authors are encouraged to rewrite the abstract containing the goal of the study, design of the experiments, key findings and how these findings could contribute to the industry or lay a foundation for further research. Also, it may be a good idea to avoid using abbreviations in the abstract. These recommendations are purely to improve the readability and to make it easier to comprehend the manuscript for the reader.

 

 

Keywords:

 

-          The selection of keywords sounds appropriate

 

Author Response

Dear Reviewer,

Thank you for your time and favourable review.
Below are the answers to your comments.

Comment 1: Abstract is within the word limits. However, it is talking more about the statistics. Authors are encouraged to rewrite the abstract containing the goal of the study, design of the experiments, key findings and how these findings could contribute to the industry or lay a foundation for further research. Also, it may be a good idea to avoid using abbreviations in the abstract. These recommendations are purely to improve the readability and to make it easier to comprehend the manuscript for the reader.

Answer:

The Abstract has been changed.

Abstract: The study aimed to evaluate the quality of selected oils from seeds of herbs and vegetables (basil, fenugreek, coriander, tomato, garden cress, parsley and dill), especially their oxidative stability. The oils were tested for oxidation degree (acid value, peroxide value, p-anisidine value, TOTOX indicator, specific extinction under ultraviolet light), colours, content of carotenoid and chlorophyll pigments, fatty acid composition, indicators of lipid nutritional quality, oxidative stability and oxidation kinetics parameters (Rancimat). Principal Component Analysis was applied to identify a correlation between oils' quality parameters. The results of fatty acid composition show that basil oil was a good source of omega-3 fatty acids. Coriander seed oil was found to be the most resistant to oxidation, containing mainly monounsaturated fatty acids. The highest value of activation energy was calculated for fenugreek oil (94.18 kJ/mol) and the lowest for dill seed oil (72.61 kJ/mol). However, basil oil was characterised by the highest constant reaction rate at 120°C – 3.0679 h^-1. The colour determined by the L* parameter and the calculated oxidizability value had the most significant influence on the oxidation stability of oils, and the correlation coefficient was r = -0.88 and 0.87, respectively.

Author Response File: Author Response.docx