Review Reports - Unlocking Essential Oils’ Potential as Sustainable Food Additives: Current State and Future Perspectives for Industrial Applications

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is a very long paper and it is repetitive. "Bioactive" is used twice in the same sentence (line 14-15). There are too many abbreviations given that are used only once (eg line 326 CH-NLC, line 400 LCEO, line 467 AEO and VOO) and others that are used in the same sentence as their full form (eg DP in line 309), and another that is used without explanation (line 286 EC). What is meant by line 407 englobes? and on line 344 do you really mean to say thymus? Lines 231-232 and 292-4 do not make sense. What is "de" in line 170? Is "hance" in line 592 the correct word? What does "onto-genetic" (line 101) mean? how is it different from genotype-environment interventions?

I struggle with several aspects of the thesis for this paper - 1. There is the inference that EOs are sustainable, safe and "guarantee safe foods" (line 22) and that synthetic compounds are less safe than 'natural' ones but whilst this might seem logical it's not true. Many EOs are highly toxic (eg pennyroyal oil Mentha pulgium). 2. That legislation needs to adapt so that more EOs can be used (lines 231). No, legislation is used to interpret data to see if something is safe for use in food; if the data isn't there for EOs then the data needs to be collected. 3. Patents are not a very good indicator of commercialisation success or likelihood. Many natural compounds cannot be patented because their use is not novel, nor is there any inventive step, or their patent has expired. For this reason the analysis done in section 7 is not a fair reflection of the commercial utility of EOs.

Author Response

Response to reviewers’ comments

Manuscript ID: sustainability-3489809

Unlocking Essential Oils Potential as Sustainable Food Additives: Current State and Future Perspectives for Industrial Applications

Authors: Israel Bautista Hernández, Ricardo Gómez-García *, Guillermo

Cristian Guadalupe Martínez-Ávila*, Nancy Medina-Herrera, María Dolores

González-Hernández

The authors deeply appreciate the attention demonstrated to our work and the possibility to reconsider a revised version of this research review. All comments and suggestions were considered that significantly led to improve our research article. The authors responses are given just after the transcription of each corresponding reviewers’ comments.

Review 1:

We appreciate the reviewer's suggestions for improving our manuscript, which we have fully addressed. In the revised version, you will find the changes highlighted in green color.

This is a very long paper, and it is repetitive. "Bioactive" is used twice in the same sentence (line 14-15).

Answer:

This observation was corrected: “Its beneficial properties have been mainly related to the presence of bioactive molecules such as…” on lines 14- 15.

There are too many abbreviations given that are used only once (eg line 326 CH-NLC, line 400 LCEO, line 467 AEO and VOO) and others that are used in the same sentence as their full form (eg DP in line 309), and another that is used without explanation (line 286 EC).

Answer:

This observation was corrected, we remove all the unnecessary abbreviation: On lines 331-332, 408, 476 and 477.
We correct the “DP” abbreviation “The incorporation of EOs has been explored in different DPs.” On line 315.
The abbreviation “EC” is “EO”, it was a mistake in the writing process. On line 265

What is meant by line 407 englobes? and on line 344 do you really mean to say thymus?

Answer:

Line 415- We have written the paragraph to improve understanding: “On the other hand, Molet-Rodríguez et al. [94] evidenced that the interaction between EOs and the food matrix (apple juice) englobes a complex mechanism. Their study found that the nutritional components (fructose, sucrose, and glucose) could help bacteria to mitigate the negative impacts of added antimicrobial EOs.”
Line 350- We have addressed the observation, and in the revised version, you can find the full name associated with the studied plant “Thymus fedtschenkoi”.

Lines 231-232 and 292-4 do not make sense.

Answer:

Line 233-240 (Revised version)- The authors re-wrote the sentence for a better understanding. “The potential future substitution of conventional antioxidant with natural antioxidant presents an interesting scope for research. However, a challenge to overcome is the lack of development and/or specification of the current legislative framework regarding the incorporation of natural antioxidants in foods. In the case of EO, Gutiérrez-Del-Rio et al. [41] highlighted the lack of specified information about the case of European regulations, due to there is no specific category for natural antioxidants related with the amounts and permissions for the use of natural additives in official tables according to European Food Safety Authority (EFSA).”

What is "de" in line 170? –

Answer:

Line 173- This was a mistake, and it was corrected int the revised version.

Is "hance" in line 592 the correct word?

Answer:

Line 602- This was corrected, according to the official patent “CN113080249 - Application method of zingiber corallinum Hance essential oil in preparation of edible spray for prolonging shelf life of vegetables and fruits”. "Hance" in Zingiber corallinum Hance refers to the botanist who first described and classified this plant.

What does "onto-genetic" (line 101) mean? how is it different from genotype-environment interventions?

Answer:

The “ontogenetic” englobes the entire sequence of events involved in the development of an organism. Thus, Verma et al. (2015) highlighted that the different ontogenic stages may affect the concentration of various primary and secondary plant products. In contrast, genotype-environment interventions are related with the phenotype, which is altered as a function of environment/ genotype. Thus, both concepts include factors that can affect plant development and the production of EOs: onto-genetics (growth stage) and environment/genetics interaction (stress conditions that promote the production of secondary metabolites).

Reference:

Verma, N.; Shukla, S. Impact of various factors responsible for fluctuation in plant secondary metabolites. Jarmap, 2015, 2 (4), 105-113, https://doi.org/10.1016/j.jarmap.2015.09.002

I struggle with several aspects of the thesis for this paper –

There is the inference that EOs are sustainable, safe and "guarantee safe foods" (line 22) and that synthetic compounds are less safe than 'natural' ones but whilst this might seem logical it's not true. Many EOs are highly toxic (eg pennyroyal oil Mentha pulgium). That legislation needs to adapt so that more EOs can be used (lines 231). No, legislation is used to interpret data to see if something is safe for use in food; if the data isn't there for EOs then the data needs to be collected.

Answer:

This point was addressed through the following paragraph (Lines: 692-701):

Finally, it is important to highlight the lack of information on other EOs, as well as the need to further investigate the area of toxicology, ensuring consumer safety. Addition-ally, some essential oils, such as Citrus aurantium L, have already been explored in the area of animal feed, determining the maximum safe concentrations for animals in human food [121]. This highlights an area of interest in the food industry for the potential application of EOs as additives in animal feed”.

Patents are not a very good indicator of commercialisation success or likelihood. Many natural compounds cannot be patented because their use is not novel, nor is there any inventive step, or their patent has expired. For this reason the analysis done in section 7 is not a fair reflection of the commercial utility of EOs.

Answer:

a) We agree with your point that it is not an indicator of "Commercialization success". However, in the review, we consider the presence of patents as an indicator of "Technological development" which could lead to commercial success if translated into an innovative and attractive product for consumers. That said, the objective of the "Intellectual Property" section in the document is not to evaluate or discuss the commercialization of Eos, but rather to highlight the "Technological development" achieved in recent years through the incorporation of Eos. This development could be used to create new production processes and potentially lead to commercial success, while ensuring he sustainability of their application.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Editor,

I have carefully read the work titled "Unlocking Essential Oils Potential as Sustainable Food Additives: Current State and Future Perspectives for Industrial Applications" by Bautista-Hernández et al. Generally, the authors successfully indicated the utility of essential oils in this context. Therefore, this reviewer suggests that this study is potentially suitable for publication in Sustainability, after minor revisions are made to improve the quality of the content and writing. Some comments on the content are:

Line 49. In the sentence “on Atractylodes macrocephala Koidz or Bassia muricata” Replace “or” with “and”. In this contest, what is the significance of referencing these two specific species here?

Line 191. For a more comprehensive explanation of antioxidant activity, please refer to the following publications to enhance the chapter's description.

Riccardo Amorati, Mario C. Foti, and Luca Valgimigli, Journal of Agricultural and Food Chemistry 2013 61 (46), 10835-10847. DOI: 10.1021/jf403496k
Bhavaniramya, Sundaresan, et al. "Role of essential oils in food safety: Antimicrobial and antioxidant applications." Grain & oil science and technology 2.2 (2019): 49-55. DOI: 10.1016/j.gaost.2019.03.001

Line 238. For insights into antimicrobial activity, please also refer to this recent review:

Wang J, Zhao F, Huang J, Li Q, Yang Q, Ju J. Application of essential oils as slow-release antimicrobial agents in food preservation: Preparation strategies, release mechanisms and application cases. Crit Rev Food Sci Nutr. 2024 Jun;64(18):6272-6297. DOI: 10.1080/10408398.2023.2167066.

Consider adding a paragraph addressing the potential toxicity of essential oils, possibly highlighting whether their effects are concentration-dependent. This could include their impact on the foods themselves (e.g., phytotoxicity on plant-based foods) as well as on the final consumer, whether human or other animals. It would also be valuable, from a regulatory standpoint, to explore whether and which essential oils are FDA-approved for food preservation, as well as the specific contexts in which they are permitted.

Author Response

Response to reviewers’ comments

Manuscript ID: sustainability-3489809

Unlocking Essential Oils Potential as Sustainable Food Additives: Current State and Future Perspectives for Industrial Applications

Authors: Israel Bautista Hernández, Ricardo Gómez-García *, Guillermo

Cristian Guadalupe Martínez-Ávila*, Nancy Medina-Herrera, María Dolores

González-Hernández

Reviewer 2:

We appreciate the reviewer's suggestions for improving our manuscript, which we have fully addressed. In the revised version, you will find the changes highlighted in blue color.

Answer:

Dear Reviewer, We appreciate your detailed evaluation of the manuscript and apologize for the error. Indeed, these are two separate species; in the revised version, you will find the proper distinction. Line 49.
Its relevance lies in being an example of new species as a source of EOs, in contrast to highly studied species such as: Oregano, Laurel, Peppermint, orange, among others. Likewise, our purpose is to highlight that the exploration of new sources remains an area of interest for the scientific community in the search for new potential bioactive ingredients. However, the direction of current scientific development is not confined to this approach, as other innovative perspectives are now emerging.

Line 191. For a more comprehensive explanation of antioxidant activity, please refer to the following publications to enhance the chapter's description.

Riccardo Amorati, Mario C. Foti, and Luca Valgimigli, Journal of Agricultural and Food Chemistry 2013 61 (46), 10835-10847. DOI: 10.1021/jf403496k
Bhavaniramya, Sundaresan, et al. "Role of essential oils in food safety: Antimicrobial and antioxidant applications." Grain & oil science and technology 2.2 (2019): 49-55. DOI: 10.1016/j.gaost.2019.03.001

Line 238. For insights into antimicrobial activity, please also refer to this recent review:

Wang J, Zhao F, Huang J, Li Q, Yang Q, Ju J. Application of essential oils as slow-release antimicrobial agents in food preservation: Preparation strategies, release mechanisms and application cases. Crit Rev Food Sci Nutr. 2024 Jun;64(18):6272-6297. DOI: 10.1080/10408398.2023.2167066.

Answer:
1. We have analyzed the literature and added the references we consider most relevant to the objective of the article.

“For example, López et al. [36] and Amorati et al. [37]) defined three antioxidant class according to their action mechanisms: the “Preventive antioxidants”, where the antioxidant interfere with the initiation process; the “chain-breaking antioxidant” (phenolic terpenes), where a phenolic group in the chemical structures donates a hydrogen atom to a lipid radical; and the “termination-enhancing antioxidant”, which involves the production of a non-phenolic terpene radical that interact with a radical leading to a termination reaction.” On lines 210 - 216

Answer:

This point was addressed through the following paragraph:

“The interest in the incorporation of EOs in the food industry is accompanied with scientific literature supporting their potential application as green additives (antioxidants and antimicrobials) [118]. However, the food regulation and safety represent one of the biggest challenges in achieving their full acceptance and application in the market. As, Donsi et al. [119] pointed out the complexity of standardizing EOs is due to their variable and complex mixture of multiple components. However, Tamburlin et al. [120] conducted a toxicological study on EOs used as food supplements (Oregano, Eucalyptus, peppermint, among others), highlighting: 100, 150, and 225 mg/day (60 kg consumer) as recommended daily doses. Meanwhile, Synadiet (Syndicat National des Compléments Alimentaires) establishes similar values: 150, 150, and 300 mg/day (70 kg/consumer). Finally, it is important to highlight the lack of information on other EOs, as well as the need to further investigate the area of toxicology, ensuring consumer safety. Addition-ally, some essential oils, such as Citrus aurantium L, have already been explored in the area of animal feed, determining the maximum safe concentrations for animals in human food [121]. This highlights an area of interest in the food industry for the potential application of EOs as additives in animal feed” – On lines 692-707.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The methodology section provides a comprehensive overview of conventional and non-conventional extraction techniques for essential oils (EOs), including hydro-distillation, steam-distillation, supercritical fluid extraction, microwave extraction, and ultrasound-assisted extraction. However, greater clarity on the experimental setup is needed. Specifically, details on sample preparation, extraction conditions, and the specific equipment used should be provided to enhance reproducibility. Additionally, the selection of extraction methods should be justified by explaining why certain techniques were chosen over others. If multiple methods are compared, explicit criteria such as yield, purity, and sustainability should be outlined.

While the discussion references similar studies, it could better emphasize how the findings align or differ from previous research. Directly comparing key chemical compounds across studies, presented in tables or figures, would improve clarity and strengthen the analysis. To enhance the discussion, the authors may benefit from reviewing the article "https://doi.org/10.3390/plants11192488," which provides relevant insights into EO applications, extraction methods, and bioactive properties.

Furthermore, the discussion should acknowledge potential limitations, such as high production costs or the limited scalability of some green extraction techniques. Addressing these challenges would provide a more balanced perspective and highlight areas for future research and industrial application.

Author Response

Response to reviewers’ comments

Manuscript ID: sustainability-3489809

Unlocking Essential Oils Potential as Sustainable Food Additives: Current State and Future Perspectives for Industrial Applications

Authors: Israel Bautista Hernández, Ricardo Gómez-García *, Guillermo

Cristian Guadalupe Martínez-Ávila*, Nancy Medina-Herrera, María Dolores

González-Hernández

Reviewer 3:

We appreciate the reviewer's suggestions for improving our manuscript, which we have fully addressed. In the revised version, you will find the changes highlighted in red color.

Answer:

Dear Reviewer, We appreciate your comments and agree with your point. As a result, in the revised version, you can find:

An emphasis on the stabilization processes of the raw material prior to the extraction processes.

Generally, the extraction process starts with the removal of impurities (e.g. dirt, insect, or another external material) followed by a drying process. The recovered dried sample is suitable according to standard procedures for extraction, which could employ different extraction times and techniques, as well plant parts (leaves, flowers, seeds, or the whole plant). On lines. 113-117.

An emphasis on the sustainability of the process and scalability.

“Additionally, the sustainability of conventional methods such as HD has been evaluated by Katekat et al. [17], their findings highlighted that the carbon footprint of conventional HD is higher compared with non-conventional or hybrid methods.” On lines 126-128

“Generally, the extraction process starts with the removal of impurities (e.g. dirt, insect, or another external material) followed by a drying process. The recovered dried sample is suitable according to standard procedures for extraction, which could employ different extraction times and techniques, as well plant parts (leaves, flowers, seeds, or the whole plant).” On lines 137-142

Answer:

We have analyzed the literature and added the references we consider most relevant to the objective of the article. This point was addressed through the following paragraph which encompasses the molecules mainly associated with the bioactivities, which can be found in some of the essential oils shown in Table 2 and in the corresponding bioactivity sections. Additionally, the main components and their percentages were added in the studies that presented them.

“Additionally, Bhavaniramya et al. [45] associated the antimicrobial activity with the main component of EOs as: cinnamaldehyde, citral, carvacrol, eugenol, or thymol (phenols), and other compounds (ketones as: β-myrcene, α-thujone, or geranyl acetate). The main action mechanisms of EOs involve among others [46,47], with the specific mechanism will depending on the chemical composition of the EOs.” On lines 250 – 255.

“Nourmohammadi et al. [79] evaluated a whey protein/nano clay bio-composite with Thymus fedtschenkoi EO (Thymol, 40.67 %; carvacrol, 46.61%; and endo-borneol, 1.68 %) and resveratrol in Liqvan cheese” on lines 347 - 349.

“Da Silva et al. [82] integrated olegels with orange EO, resulting in bread with decreased hardness, high storage stability (20 days), and reduced mold growth related with the chemical composition (limonene, 95.95 %; β-myrcene, 1.76 %; β-linalool, 0.98 %).” On lines 372 – 375.

“Similarly, Dai et al. [92] reported that Litsea cubeba EO shows potential against other pathogenic bacteria such as enterohemorrhagic E. coli 0157:H7 in 4 vegetable juices (bitter gourd, cucumber, carrots, and spinach) stored at 4 °C for 4 days; the study suggests that Citral (Main component) can impede bacterial nucleic acid replication.” On lines 405 - 409.

“Lages et al. [102] evaluated an alternative to synthetic chemical preservatives (nitrites) in meat sausage using thyme EO with a high carvacrol content (54.5%) and o-cymol (26.9 %).” On lines 444 - 446.

“The potential of EOs as active components has been tested in active packaging using different technologies, such as nanofibrous films (0.5, 1, 2 %) encapsulated with Mentha longiflora L. EO with main component as: Pulegone 47.20 %, Eucalyptol 22.72 % and Menthone 13.44 %, which showed a reduction in bacterial counts” On lines 459 – 462.

Author Response File: Author Response.pdf