Nutritional Quality of Conventional, Organic, and Hydroponic Tomatoes Commercialized in Quito, Ecuador

Round 1

Reviewer 1 Report (Previous Reviewer 1)

Comments and Suggestions for Authors

Include “Tomatoes” as a keyword, since it is the plant material studied in this work.

Figure 1. Include letters above the bars.

Figure 2. The statistic is not appropriate. You need to compare each sample for Cu, Fe, Mn and Zn separately. The letters need to be signed above each histogram.

Why didn't you use more recent references for comparison? If possible, include more recent information of content.

Author Response

Response to Reviewer 1 comments

Comments and Suggestions for Authors

Comment R1:  Include “Tomatoes” as a keyword, since it is the plant material studied in this work.

Response: The key word “tomatoes” has been included.

Comment R1:  Figure 1. Include letters above the bars.

Response: Figure 1 has been edited.

Comment R1:  Figure 2. The statistic is not appropriate. You need to compare each sample for Cu, Fe, Mn and Zn separately. The letters need to be signed above each histogram.

Response: Figure 2 has been edited.

Comment R1:  Why didn't you use more recent references for comparison? If possible, include more recent information of content.

Response: New and recent references for comparison were included (lines 463 – 465; 479 – 483; 531 – 534).

 Author Response File: Author Response.pdf

Reviewer 2 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

The authors replyed to all Reviewers’requests, thus improving the quality of their manuscript.

However, there are still few things that should be further improved:

It is not still clear if 30 samples refers to the sum of conventional, organic and hydroponic tomatoes, or if 30 samples of each type of tomatoes were collected. Please specify the number of each type of tomatoes sampled and add it in the manuscript, as well as in the relevant Tables. Is the “outlier sample” included in these 30 samples?

Page 8, Table 2: statistical significance should be also added to the last two lines.

Page 10, Figure 2: the way the statistically significant differences are expressed is not very clear. I suggest the use of different letters. Idem for Figure 1

Page 12, lines 499-501: “Additionally, our results for conventional tomatoes showed slightly higher levels of Fe, while hydroponic samples had slightly higher concentrations of Mn.” This sentence is partially correct. Please modify (if statistical analysis is correct) in: “Additionally, our results for conventional tomatoes showed slightly higher levels of Fe, even if not statistically significant, while hydroponic samples had slightly higher concentrations of Mn (p<0.05).”

Author Response

Comment R1: It is not still clear if 30 samples refers to the sum of conventional, organic and hydroponic tomatoes, or if 30 samples of each type of tomatoes were collected. Please specify the number of each type of tomatoes sampled and add it in the manuscript, as well as in the relevant Tables. Is the “outlier sample” included in these 30 samples?

Response: Line 123 was edited, specifying that the 30 samples of each type of tomatoes were collected. In Tables 1, 2, and 4, the number of samples has already been included.

Line 367 was edited specifying that one specimen from the hydroponic samples was discarded, as it was considered an outlier.

Comment R1: Page 8, Table 2: statistical significance should be also added to the last two lines.

Response: Statistically significance was included in the last two lines in Table 2.

Comment R1: Page 10, Figure 2: the way the statistically significant differences are expressed is not very clear. I suggest the use of different letters. Idem for Figure 1

Response: The presentation of the statistically significant differences in Figures 1 and 2 has been edited. Lines 346-347, 381-382.

Comment R1: Page 12, lines 499-501: “Additionally, our results for conventional tomatoes showed slightly higher levels of Fe, while hydroponic samples had slightly higher concentrations of Mn.” This sentence is partially correct. Please modify (if statistical analysis is correct) in: “Additionally, our results for conventional tomatoes showed slightly higher levels of Fe, even if not statistically significant, while hydroponic samples had slightly higher concentrations of Mn (p<0.05).”

Response: The statistical analysis was revised and lines 500-502 were edited according to the reviewer´s suggestion. It must be considered that p>0.05 was corrected, as the t test was used.

Author Response File: Author Response.pdf

Reviewer 3 Report (Previous Reviewer 3)

Comments and Suggestions for Authors

The manuscript gives an accurate description of nutritional quality and safety of tomato fruits coming from different cultivation systems (traditional, organic, hydroponic). The descriptions of analytical methodologies are very precise and accurate.

the authors have responded adequately and provided much guidance

However, the great variability of the samples analyzed with respect to the number of analyses performed did not allow, for some parameters, to indicate the best product.

 In Figure 2 and text line 373-374 for Mn is not clear if the differences are between all the typology

Adjust the figure

Line 382-383: eliminate “except for manganese”

Author Response

Comment R2:  However, the great variability of the samples analyzed with respect to the number of analyses performed did not allow, for some parameters, to indicate the best product.

Response: In our study, we found certain differences regarding antioxidant and micronutrient levels. Indeed, it is not possible to indicate the best product; however, other studies have also reported that there is no “best option”, for example between organic or conventional types of crops (doi:10.1016/j.foodchem.2015.07.008 and doi:10.1051/agro/2009019).

 Comment R2:  In Figure 2 and text line 373-374 for Mn is not clear if the differences are between all the typology.

Adjust the figure

Response: The presentation of the statistically significant differences in Figure 2 has been edited.

Lines 370-373 were edited to clarify.

Comment R2:  Line 382-383: eliminate “except for manganese”

Response: “Except for manganese” was eliminated from line 385.

Author Response File: Author Response.pdf

Reviewer 4 Report (New Reviewer)

Comments and Suggestions for Authors

Total phenolic content should be presented as g or mg gallic acid equivalent (GAE) per fresh weight.

I have major concerns regarding the statistical analysis of data in this manuscript. How did the authors perform the analysis? Which approach was used? parametric or nonparametric? Please clearly state the analysis.

Authors are suggested to perform another assay to measure antioxidant capacity to confirm (support) DPPH, such as FRAP and/or ABTS.

Comments on the Quality of English Language

Minor revision is suggested. 

Author Response

Comment R3:  Total phenolic content should be presented as g or mg gallic acid equivalent (GAE) per fresh weight.

Response: Line 189 was edited including the units for total phenolic results as “milligrams gallic acid equivalent (GAE) per 100 grams of fresh weight (FW)”. Also, units for total phenolics in Table 1 were edited.

Comment R3:  I have major concerns regarding the statistical analysis of data in this manuscript. How did the authors perform the analysis? Which approach was used? parametric or nonparametric? Please clearly state the analysis.

Response: The statistical data analysis for the present study had a parametric approach. This information was included in line 274.

Comment R3:  Authors are suggested to perform another assay to measure antioxidant capacity to confirm (support) DPPH, such as FRAP and/or ABTS.

Response: Authors appreciate the reviewer´s suggestion; however, according to the revised bibliography (doi.org/10.3390/ijms22073380), DPPH test is commonly applied to produce significant and comparable results for the estimation of the total antioxidant content in foods. In our study, beyond the DPPH test we determined the content of several individual antioxidants (ascorbic acid, lycopene, and unsaturated fatty acids) in order to show its content in different tomatoes types.

Comment R3:  Comments on the Quality of English Language

Minor revision is suggested.

Response: English language was revised throughout the whole document.

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report (New Reviewer)

Comments and Suggestions for Authors

Line 274: which parametric approach? t-test? ANOVA? Please specify. Moreover, please add the p value. 

Author Response

Response to Reviewer 4 comments

Comments and Suggestions for Authors

Comment R3:  Line 274: which parametric approach? t-test? ANOVA? Please specify. Moreover, please add the p value.

Response: Lines 274, 276-279 were edited.

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

• - Line 11-14. Please rewrite the first two sentences. It's confusing and does not highlight the aim of the study.   

• - Point the novelty of this study in abstract. 

• - Revise the citations throughout the whole manuscript and reference style.   

• - Line 116. Add the information about freeze-drying conditions.  

• - Line 122. You should choose a "dry sample" or "freeze-dried" sample. Please uniform this. 

• - Line 138. Same comment. “dry sample” or “freeze-dried” or “lyophilized”. -Uniform this in whole manuscript.  

• - Table 1. Why did you express results in fresh weight? Please indicate the units for each method in the methodology part. 

• - 2.7. Free RSA determination – What is the unit? Why did you use the gallic acid as a standard? For comparison, you should use some synthetic antioxidants, like Trolox, or BHA, BHT. It is also important for comparison with data from scientific literature.  

• - For antioxidant activity determination, at least three assays with different mechanism are required.  

• - Table 1. Indicate letters for statistic presentation as superscript. 

• - Figure 2. Statistics is required.  

• - Avoid citations in the conclusion part. 

Dear Authors, 

After reviewing this paper, my opinion is that the entire manuscript needs a deep and serious revision by the authors, before any attempt to submit it to Foods. 

Results are a weak section and poor in data to a full paper. The novelty in this manuscript is low. The organization of the whole study is not appropriate. You have thirty samples of conventionally, organically, and hydroponically grown tomatoes acquired between 2020 and 2021. Statistics need to be more comprehensive.

Reviewer 2 Report

Comments and Suggestions for Authors

General consideration about the manuscript:

Variety, season, harvest time, maturity, as well as environmental factors (i.e. light, water and nutrient supply) affect the antioxidant content of tomatoes [Dumas et al. 2003, Journal of the Science of Food and Agriculture, 83:369-382]. In particular, environmental conditions have a great effect on the content of vitamin C in tomatoes (exposure to light is a favorable factor for ascorbic acid accumulation [Dumas et al. 2003, Journal of the Science of Food and Agriculture, 83:369-382. Martínez-Valverde et al. 2002, Journal of Science Food and Agriculture, 82:323-330.]. Furthermore, fertilizers rich in soluble nitrogen could cause a decrease in the content of ascorbic acid, since the nitrogen supply increased the plants’ leaf density, promoting shading over the fruits [Zoran, Ilić S., Kapoulas Nikolaos, and Sunic Ljubomir. "Tomato fruit quality from organic and conventional production." Organic agriculture towards sustainability. Rijeka, Croatia: In Tech Europe (2014): 147-169]. Therefore, in order to compare results from organic vs conventional tomaotes, it is important to compare tomatoes that are planted and harvested during the same season of the year and that originate from regions with similar incidence of solar radiation.

Also tomato micronutrient content is affected by cultivar [Ordonez-Santos et al. 2011, International Journal of Food Science and Technology, 46(1): 561-568]

For all these reasons, as also stated by the authors in the Conclusion section, buta abov all beacause the results of this work do not come from experimental cultivations of tomato made by the authors, I suggest adding in the title “commercially….tomatoes from Quito, Ecuador”

The literature about hydroponically grown tomato cited by the authors is very poor. Please add the relevant refernces in the manuscript and refer to them when discussing results.

In many cases, the authors reported only references in agreement with their results or where organic tomatoes were “better” than conventional ones. Actually, many contradictory results are reported in the literature concerning major contents of health positive compounds in organic tomato compared to conventional ones. Please cite also these references in the manuscript [Rossi et al. 2008, European journal of nutrition 47: 266-272 is only an example].

Further comments to the manuscript:

Page 2, lines 67-69-90: “Tomato is an important source of minerals, including…” From the way the sentence is written it would seem that even sodium and heavy metals are considered a positive matter in tomato. I suggest changing the sentence in “Tomato  conatin many minerals, including macro-…, micro-…. and heavy metals…” also because tomato cannot be considered a good source of mineral (the contents of each mineral should be evaluated based on the recommended servings of the food and the recommended intakes of nutrient)

Page 2, lines 89-90: The authors stated “No information has been found related to the content of nutrients, minerals, or contaminants in hydroponic tomato crops”. This is not true, even because the authors contradicted themselves (in page 7 lines 284-286, 298-299, page 11 lines 451-453). Please cite different works in the literature on the matter and refer to them when discussing results [Anza et al. 2006, Journal of food quality 29: 16-37. Mitsanis et al. 2021, Horticulturae, 7: 311. Roosta et al. 2013, Journal of plant Nutrition, 36(13), 2070-2083 are only an examples].

Page 6, lines 266-267: “…including studies on Ecuadorian products” This sentence is inconsistent with that previously stated by the authors (page 2, lines 96-99: “To the best of our knowledge, no previous chemometric studies on antioxidant compounds and potential free radical scavenging activity (free RSA) in Solanum lycopersicum grown using conventional, organic, and hydroponic methods have been conducted in Ecuador”). Please better explain or correct the sentences. Idem for lines 280-281 (page 2)

Page 7, Table 2: statistical significance is lacking. Please add.

Page 10, Lines 363-379: This entire paragraph has nothing to do with the discussion of the results. If anything, it should be moved, in a shortened form, to the Introduction section. Idem for page 11, lines 408-417.

Comments on the Quality of English Language

Minor editing of English language is required

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript gives an accurate description of nutritional quality and safety of tomato fruits coming from different cultivation systems (traditional, organic, hydroponic). The descriptions of analytical methodologies are very precise and accurate.

The description of the fruit sampling methodology is very general 

Is no clear if the authors analysed tomato of different variety, coming for different regions, in different period of the year, produced in different cultivation conditions like greenhouse or open filed (organic or conventional).

Some information should have been on the label, although I do not know the labelling laws in Equador.

Others information very important on determining fruit quality like fertilization, soil, etc. are impossible to detect by collecting fruits on supermarket.

Furthermore, no analysis were carried out to determine the degree of ripeness of the fruit (colour, firmness, sugars, etc.)

As the authors indicate in the discussion and conclusion:

“Regarding AA, it has been demonstrated that levels in tomatoes increase to a maximum value and then decrease during the ripening process; thus, AA content is lower in tomatoes picked when fully ripe compared to those picked at the mature green stage and 388 ripened off the vine (94)”

 “however, phenolics’ levels vary widely 404 and may be affected by ripeness, genotype, and cultivation system (97)”

 “The difference in antioxidants and their free RSA between the three tomato types may be attributed to several factors, particularly cultivar genetic variability, water availability, farming location, light exposure, temperature, degree of fruit ripeness at harvest, mineral nutrition (13,106), and agricultural practices (e.g., irrigation, fertilization, etc.), all of which affect plants’ production of secondary metabolites (33,106). Evaluating variation in antioxidant content and free RSA in real-time is very complex and also depends on how fruit is stored and transported (33,106). However, a general approach involves analyzing products commercially available for consumption, which represents what people are truly consuming and was our selected method in the present study.  

Pernice et al. (106) showed that particular agricultural practices facilitate the modulation of antioxidant concentration in tomatoes; irrigation and biotype affected flavonoid concentration in fresh and processed tomatoes, while antioxidant activity, irrigation, and biotype were only significant for processed tomatoes.  

As with essential nutrients and antioxidants, trace metal content is also influenced by cultivar, cultivation method, growing conditions, production region, and sampling period (80,82)”

“the cultivar, harvest time, genetic and agricultural factors, growing conditions, and production region directly in fluence the nutritional and nutraceutical properties of the final product”

so if you do not take all these factors into account but want to make a more general comparison of the quality and healthiness of commercial tomatoes, you probably need to do a more complex experimental design

Line 85 89: this sentence is not accurate. Please rewrite. Conventional and organic tomato production can be done in open filed or in greenhouse like idroponic.

Line 89-92: this sentence is not accurate. Please rewrite.

Line 107-108: you indicate that you acquired 30 samples of conventionally, organically and hydroponically tomatoes from supermarket between 2020 and 2021. Is not clear if the 30 samples per cultivation system were bought at the same time or in different period of the year, if you bought fruit of the same variety, commercial category ripening stage, etc. Please give more information.

Please respond to these remarks.

In Table 1 and table 4 are reported Range values. It does not seem appropriate to indicate the range values found in the bibliography in the tables, and especially not in this format. The number of samples (n=30) must be indicated in the caption

Line 261-262: if you declare that there are no AA data for Hydroponic How can you report range values in table?

Line 262-263: variable dates. the fact that the values are highly variable is in line with what you wrote earlier. i.e. that tomato varieties, open field-greenhouse, fertilization, harvest period and stage of ripening greatly influence the quality of the fruits.

In table 2 caption you must indicate the n of samples, mean, standard deviation, … like table 1.

Why there is not a statistical analysis for fats?

Fig. 2 Caption: you write The results 334 from one sample of hydroponic tomatoes were not considered, as these were the highest within the 335 group.  it was an outlier?

Why there is not a statistical analysis of data?

Table 4: Why there is not a statistical analysis of data?

348-349: you have set up an experimental design with 30 samples and reported the averages in the table. then in the results you talk about a value which you do not quantify in the text and which is clearly not present in the table

380-382: what you write is not correct. You do not take into account the statistical analysis and what you wrote in the results (lines 260-262 and 305-306)