Effect of Drying Post-Harvest on the Nutritional Compounds of Edible Flowers
, Giulia Carmassi 1, Barbara Ruffoni 4, Andrea Copetta 4,* and Laura Pistelli 1,5Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsPlease add a sentence that would connect the text passages, not just jump to the Callianthe megapotamica description. Instead of broad description of several edible species in the introduction section, please provide the state of the matter across the globe, then in Europe, and finally in Italy well known for their knowledge regarding the edible flowers and edible weeds.
Those descriptions belong more to the material section. After the part stating: Therefore the aim of this study was to investigate the chemical composition of the C. megapotamica, C. striata, N. strumosa and S. elegans; as well as the effects of different post-harvest techniques in their quality and bioactive metabolites composition.
Some plants were grown in soil, others in pots, some in organic way, others not... Besides species influence, we here have the influence of cultivation method. Plants grown in pots are more stressed than others and might produce more protective compounds - the ones we consider most important for human consumption... please explain why you opted for such trial design and how are you going to mitigate the effect of cultivation practices in order to compare obtained results?
Add statistical analyses for differences between results in table 1.
PCA: 'Similarly, the score plot of the PCA, reported in Figure 7, evidenced a clear separation of fresh samples, plotted in the left quadrant (PC1 < 0), from the treated ones, which instead occupied the right quadrants (PC1 > 0). This sharp detachment was probably determined by the lower contents of the investigated biochemical variables in the fresh plant material as all the vectors were directed toward the rightmost area of the loading plot of the PCA. The obtained separation, indeed, was plausible due to the increase of all the investigated parameters in post-harvested plant material determined by the conspicuous water loss. Concerning the treated samples, PCA was not able to discern between HA and FD ones. Conversely, the same species subjected to the two different post-harvest treatments showed a tendency to be grouped closely.'
Statisticians should revise the manuscript to obtain the correct interpretation. PCA clearly provides results that imply which component placed samples on the given place in the plot, there is no place for 'maybe' or 'probably'.
The conclusion section should be more concise with metrical values and future recommendations.
Author Response
1. Please add a sentence that would connect the text passages, not just jump to the Callianthe megapotamica description. Instead of broad description of several edible species in the introduction section, please provide the state of the matter across the globe, then in Europe, and finally in Italy well known for their knowledge regarding the edible flowers and edible weeds.
ANSWER Some additional information are added in the manuscript: “All over the world, the edible flowers that can be purchased in the supermarket are those deriving from annual or perennial herbaceous plants that can easily be grown in pots; however, there are climbers, shrubs and trees that produce edible flowers, but their cultivation requires larger spaces than edible flowers produced by herbaceous plants. In fact, in Asia among the most consumed flowers are peonies, hibiscus and Clitoria ternatea; while in Mexico the flowers of Agave salmiana, Arbutus xalapensis, Myrtillocactus geometrizans, Erythrina spp. and Yucca filifera are ingredients of traditional dishes. In Europe, like in Italy, the edible flowers mainly consumed are violets, marigolds, nasturtiums, pansies and roses. Furthermore, flowers and inflorescences like artichokes, broccoli, cauliflower and capers are part of the traditional cuisine of many countries, however they are marketed as vegetables” “Some ornamental plants that produce edible flowers are still little studied and commercialized for food purposes; among these there are Callianthe megapotamica, C. striata, Nemesia strumosa and Salvia elegans.” Lines 46-58
2.- Those descriptions belong more to the material section. After the part stating: Therefore the aim of this study was to investigate the chemical composition of the C. megapotamica, C. striata, N. strumosa and S. elegans; as well as the effects of different post-harvest techniques in their quality and bioactive metabolites composition.
ANSWER: The sentence you mentioned is at the end of the introduction. In this part of the introduction many authors and journals are required to declare the aim of the work, that is the content of this sentence lines 61-63
3-Some plants were grown in soil, others in pots, some in organic way, others not... Besides species influence, we here have the influence of cultivation method. Plants grown in pots are more stressed than others and might produce more protective compounds - the ones we consider most important for human consumption... please explain why you opted for such trial design and how are you going to mitigate the effect of cultivation practices in order to compare obtained results?
ANSWER: The two Callianthe species could not be grown in greenhouses due to their size. All the plants were grown organically, both in the open ground and in the greenhouse. we have applied the same cultivation methods that edible flower producers use. The text has been modified to better clarify the cultivation method lines 103-116
4- Add statistical analyses for differences between results in table 1.
ANSWER: The authors revised the manuscript and added the requested information in table 1. The manuscript was revised and the description of the results by potassium and manganese were corrected considering the statistical analysis. Lines 261-263
5- PCA: 'Similarly, the score plot of the PCA, reported in Figure 7, evidenced a clear separation of fresh samples, plotted in the left quadrant (PC1 < 0), from the treated ones, which instead occupied the right quadrants (PC1 > 0). This sharp detachment was probably determined by the lower contents of the investigated biochemical variables in the fresh plant material as all the vectors were directed toward the rightmost area of the loading plot of the PCA. The obtained separation, indeed, was plausible due to the increase of all the investigated parameters in post-harvested plant material determined by the conspicuous water loss. Concerning the treated samples, PCA was not able to discern between HA and FD ones. Conversely, the same species subjected to the two different post-harvest treatments showed a tendency to be grouped closely.'
Statisticians should revise the manuscript to obtain the correct interpretation. PCA clearly provides results that imply which component placed samples on the given place in the plot, there is no place for 'maybe' or 'probably'.
Answer: Some modifications have been reported in the manuscript according to the referee suggestion. The terms “probably” or “maybe” were used because the positioning of the samples in the score plot of the PCA is determined by the vectorial sum of each of the variables. Thus only considering the PCA we can do some assumptions that can be confirmed by considering simultaneously the analytical results and the statistical analyses. However, the statistical results have been rewritten to reach greater clarity.lines 509-521
6- The conclusion section should be more concise with metrical values and future recommendations.
Answer: Some additional information are added in the manuscript. Lines 532-540
Reviewer 2 Report
Comments and Suggestions for AuthorsEdible flowers, which are offered to consumers in an increasingly wide range, are, for understandable reasons, arousing the interest of nutritionists and food analysts. The growing number of articles appearing in scientific journals on edible flowers focus on two aspects: the first is ensuring the safety of consumers, and the second – assessment of the content of bioactive compounds and nutritional value.
The authors of the article "Effect of post-harvest in the nutritional compounds of edible flowers" combine the safety aspect with the analysis of the content of bioactive compounds and the nutritional value. To ensure product safety, research on post-harvest treatments is required. The authors used two methods: vacuum freeze drying and hot air drying. The next stage of the research was to determine the impact of both preservation methods on the quality of edible flowers.
The authors used correct research methods in the analysis of products of plant origin and statistically analyzed the research results. However, they omitted very important aspects of this research, including plant cultivation methods. The exotic plants Callianthe megapotamica (A. Spreng.) Dorr (Malvaceae) and Callianthe striata (Dicks. Ex Lindl.) Donnel (Malvaceae) were grown in soil conditions, while Nemesia strumosa Solander ex. Benth (Plantaginaceae) and Salvia elegans Vahl (Lamiaceae) were grown in flower pots under greenhouse conditions. However, the authors did not take this into account in the discussion of the results. The different composition of soil and potted substrates could have influenced the minerals content. Climatic conditions in garden and greenhouse cultivation could have also influenced the differentiation of the quality parameters of the studied edible flowers. Therefore, the differentiating factor may be not only the post-harvest treatment method, but also the composition of the substrates, climatic conditions and water or temperature stress, which also affect the content of bioactive compounds.
There is no mention in the methodical part about the number of repetitions of determinations for a single sample. Where the analyses conducted just once for each sample of the given flower?
The quality of figure 7 should be improved. Also, the PCA results are not fully discussed, for example, the meaning of PC1 and PC2 is not interpreted. As seen in Fig. 7, PC1 groups antioxidant properties at high positive values, while PC2 discriminates primarily between carotenoid and anthocyanin content. Furthermore, the authors do not justify the selection of just two factors, i.e., no evidence is given for the importance of further factors. The percentage of variance explained by PC2 is almost unreadable from fig. 7.
I wonder why the authors have chosen three different methods for determination of the same property (i.e., antioxidant activity), namely DPPH, FRAP, and ABTS. From fig. 7 it is clear that DPPH and FRAP measure exactly the same thing, and ABTS is only marginally different. The authors should explain the choice of three methods.
Conclusions are very rudimentary and, given the wide array of analytical techniques used, should be certainly improved.
The comments do not affect the positive assessment of the article, but I believe that the authors omitted important aspects in the discussion of the results that could have influenced the differences in the quality parameters of exotic edible flowers preserved using various methods.
The authors' research can be used when choosing the method of preserving edible flowers. Currently, research is being carried out around the world on the use of edible flowers not only for decorative purposes in gastronomy, confectionery and home cooking. The authors' research can serve these new directions of research.
Of course, the authors could focus their research on selected factors, but in the discussion they cannot ignore other factors that may influence the obtained results. These factors could have limited the research conducted by the authors and, at the same time, constituted prospects for further research.
Author Response
Edible flowers, which are offered to consumers in an increasingly wide range, are, for understandable reasons, arousing the interest of nutritionists and food analysts. The growing number of articles appearing in scientific journals on edible flowers focus on two aspects: the first is ensuring the safety of consumers, and the second – assessment of the content of bioactive compounds and nutritional value.
The authors of the article "Effect of post-harvest in the nutritional compounds of edible flowers" combine the safety aspect with the analysis of the content of bioactive compounds and the nutritional value. To ensure product safety, research on post-harvest treatments is required. The authors used two methods: vacuum freeze drying and hot air drying. The next stage of the research was to determine the impact of both preservation methods on the quality of edible flowers.The authors used correct research methods in the analysis of products of plant origin and statistically analyzed the research results.However,
1. they omitted very important aspects of this research, including plant cultivation methods.
ANSWER The text has been modified to better clarify the cultivation method. lines 103-116
2. The exotic plants Callianthe megapotamica(A. Spreng.) Dorr (Malvaceae) and Callianthe striata (Dicks. Ex Lindl.) Donnel (Malvaceae) were grown in soil conditions, while Nemesia strumosa Solander ex. Benth (Plantaginaceae) and Salvia elegans Vahl (Lamiaceae) were grown in flower pots under greenhouse conditions. However, the authors did not take this into account in the discussion of the results. The different composition of soil and potted substrates could have influenced the minerals content. Climatic conditions in garden and greenhouse cultivation could have also influenced the differentiation of the quality parameters of the studied edible flowers. Therefore, the differentiating factor may be not only the post-harvest treatment method, but also the composition of the substrates, climatic conditions and water or temperature stress, which also affect the content of bioactive compounds.
ANSWER: Additional information has been inserted into the text. lines 103-116The two Callianthe species could not be grown in greenhouses due to their size. All the plants were grown organically, both in the open ground and in the greenhouse. we have applied the same cultivation methods that edible flower producers use. The climatic conditions in garden and greenhouse cultivation could have influenced the differentiation of the quality parameters of the edible flowers studied, however in order to discuss these influences, the same species must be grown in different environments and this is not our case: we have grown the species in the environmental conditions that edible flower producers use.
3 There is no mention in the methodical part about the number of repetitions of determinations for a single sample. Where the analyses conducted just once for each sample of the given flower?
ANSWER To make the extracts we used 200 mg of fresh flowers or 20 mg of dried flowers, these amounts were taken from different flowers and then mixed to arrive at the weight used. For the biochemical determinations we used three repetitions for the same sample (extract). We added this information at the end of the methodical part. “All measurements were performed with an ultraviolet UV-1800 spectrophotometer (Shimadzu Corp., Kyoto, Japan) with three repetitions for each sample (n=3).” Lines 176-178
4. The quality of figure 7 should be improved. Also, the PCA results are not fully discussed, for example, the meaning of PC1 and PC2 is not interpreted. As seen in Fig. 7, PC1 groups antioxidant properties at high positive values, while PC2 discriminates primarily between carotenoid and anthocyanin content. Furthermore, the authors do not justify the selection of just two factors, i.e., no evidence is given for the importance of further factors. The percentage of variance explained by PC2 is almost unreadable from fig. 7.
Answer: the figure has been modified with an increased quality (line 523). Some additional information are added in the manuscript in revision mode. Lines 508-522
5. I wonder why the authors have chosen three different methods for determination of the same property (i.e., antioxidant activity), namely DPPH, FRAP, and ABTS. From fig. 7 it is clear that DPPH and FRAP measure exactly the same thing, and ABTS is only marginally different. The authors should explain the choice of three methods.
ANSWER: The three methods can detect the antioxidant activity of different compounds: ABTS method detects hydrophilic and lipophilic substances at different pH, and detects the leakage of both hydrogen and electrons. The DPPH activity detects similar leakage, but the DPPH solution can interact with some compounds that have similar wavelength of Absorbance, or great molecules that do not bind with the reactive part of DPPH. FRAP method is based only on the electron transfer to Fe3+; this last method does not include the activity of thiol groups and proteins. (see Xiao et al., Guideline for antioxidant assays for food components, Food Frontiers 202, 1, 60-69). Therefore the use of different antioxidant activities is preferred to include the variety of antioxidant compounds present in the plant samples.
Some detailed information has been added to the manuscript (material and methods and results). Lines 165-167; lines 344-352
6. Conclusions are very rudimentary and, given the wide array of analytical techniques used, should be certainly improved.
The comments do not affect the positive assessment of the article, but I believe that the authors omitted important aspects in the discussion of the results that could have influenced the differences in the quality parameters of exotic edible flowers preserved using various methods.The authors' research can be used when choosing the method of preserving edible flowers. Currently, research is being carried out around the world on the use of edible flowers not only for decorative purposes in gastronomy, confectionery and home cooking. The authors' research can serve these new directions of research.Of course, the authors could focus their research on selected factors, but in the discussion they cannot ignore other factors that may influence the obtained results. These factors could have limited the research conducted by the authors and, at the same time, constituted prospects for further research.
ANSWER: The authors revised the text line: 530-539
Reviewer 3 Report
Comments and Suggestions for AuthorsThe paper is interesting and deals with the application of drying processes on edible flowers. However, there is room for improvement which is described below:
- In the title, given that the two post-harvest treatments to be performed are drying treatments, would it not be better to talk about the effect of different drying treatments on edible flowers?
- In the summary, the most common drying treatments are mentioned, but hot air drying is not considered; this should be reviewed.
In the introduction it would be interesting to deepen on some compounds and specific situations of flowers.
In materials and methods a specific solution for irrigation of some plants is mentioned but nothing is said about the composition.
To complete the information on freeze-drying, it is necessary to add the vacuum pressure used, and the specific model of the equipment used is not mentioned.
In hot air drying, neither the equipment used nor conditions such as the speed of the air used are specified.
It is recommended to use the equation editor to write the formulas used.
In Figure 1, if the bars are all 1 cm, why do they appear with different lengths in each photo?
There is no mention of how the moisture of the samples was determined? initial and final moisture for each treatment and varieties.
Sometimes the equipment used for some measurements is not correctly identified.
How were the monomeric anthocyanins calculations performed?
It is important to inform which were the repetitions for the respective analyses.
It is important if two treatments were used, because in Figure 2 only one result is presented and it is not identified to which of the two corresponds. On the other hand, it would be interesting to know how long the respective treatments lasted.
It would have been interesting to have instrumental color measurements to later relate with the presence of carotenoids and anthocyanins.
Review and standardize the letter sizes in Figure 4.
The conclusion can be improved with emphasis on the knowledge generated and its possible applications.
Author Response
- In the title, given that the two post-harvest treatments to be performed are drying treatments, would it not be better to talk about the effect of different drying treatments on edible flowers?
ANSWER: the authors agree with the observation done by the referee and change the title in: "Effect of drying post-harvest in the nutritional compounds of edible flowers"
- In the summary, the most common drying treatments are mentioned, but hot air drying is not considered; this should be reviewed.
Answer. In the summary we described that hot air drying is more recommended to increase the antioxidant activity of C. megapotamica, N. strumosa and S. elegans. As well as the increase of ascorbic acid content in N. strumosa with this post-harvest technique.
- In the introduction it would be interesting to deepen on some compounds and specific situations of flowers.
Answer. Additional information has been inserted into the text .
- In materials and methods a specific solution for irrigation of some plants is mentioned but nothing is said about the composition.
Answer. The text has been modified to better clarify the cultivation method lines 103-116
- To complete the information on freeze-drying, it is necessary to add the vacuum pressure used, and the specific model of the equipment used is not mentioned.
Answer. the information has been added in the text - Freeze-drying was carried out at -50 °C for 48 hours (Labconco, Kansas City, USA)
- In hot air drying, neither the equipment used nor conditions such as the speed of the air used are specified.
Answer:The authors add the sentences :hot-air dried at 60°C with constant ventilation in a Tecnocal 2000 (Tecnovetro , Monza, Itraly(.until costant dry weight. (approximately 24 h)
- It is recommended to use the equation editor to write the formulas used.
Answer. the text was edited using equation editor line 128
- In Figure 1, if the bars are all 1 cm, why do they appear with different lengths in each photo?
Answer. They are different because each bar is specific to each photo. All bars have 1 cm but the photos were taken at different points to ensure a best visualization of each flower. Therefore the scale of each photo has a different scale and the specific bar corresponds to this scale.
- There is no mention of how the moisture of the samples was determined? initial and final moisture for each treatment and varieties.
Answer. The moisture (water loss) was determined by the equation mentioned in the material and methods (fresh weight - dry weight) * 100/ fresh weight. The equation was brought into greater focus in the text. line 128
- Sometimes the equipment used for some measurements is not correctly identified.
ANSWER the authors revised the manuscript and added the requested information
- Spectrophotometer: Ultraviolet-Visible spectrophotometer, SHIMADZU UV-1800, (Shimadzu Corp., Kyoto, Japan)
- Air dried instrument: Tecnocalor 2000, Technovetro Monza, IT)
- vacuum freeze-dried (FD) (Labconco, Kansas City, USA)
- atomic absorption spectrometer (Varian 240FS AA, Sidney, Australia).
- How were the monomeric anthocyanins calculations performed?
ANSWER: As reported in the reference (n. 32 in the manuscript) Giusti, M. M., & Wrolstad, R. E. (2001). Characterization and measurement of anthocyanins by UV‐visible spectroscopy. Current protocols in food analytical chemistry, (1), F1-2.
Calculate the absorbance of the diluted sample (A) as follows: A = (Aλ vis-max – A700)pH 1.0 – (Aλ vis-max – A700)pH 4.5 .
Calculate the monomeric anthocyanin pigment concentration in the original sample using the following formula: Monomeric anthocyanin pigment (mg/liter) = (A Å~ MW Å~ DF Å~ 1000)/(ε Å~ 1) where MW is the molecular weight (Table F1.2.2), DF is the dilution factor (for example, if a 0.2 ml sample is diluted to 3 ml, DF = 15), and ε is the molar absorptivity
- It is important to inform which were the repetitions for the respective analyses.It is important if two treatments were used, because in Figure 2 only one result is presented and it is not identified to which of the two corresponds. On the other hand, it would be interesting to know how long the respective treatments lasted.
Answer. In the figure 2 we showed the results of water loss and crude protein percentages. These results are made only in the dried material because the analyses used required the dried material for its determinations. For this case we used the hot-air dried flowers. Freeze-drying was carried out at -50 °C for 48 hours and the hot-air drying at 60 °C for 72 hours. We add this information in the manuscript.
- It would have been interesting to have instrumental color measurements to later relate with the presence of carotenoids and anthocyanins.
ANSWER The authors did not measure the color by the instrument since some flowers (as Callianthe megapotamica) have petals of two different colors, so it was not possible to standardize the method
- Review and standardize the letter sizes in Figure 4.
Answer. The authors revised and changed the letter sizes in Figure 4.
- The conclusion can be improved with emphasis on the knowledge generated and its possible applications.
Answer. The authors revised the text
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThank you for implementing necessary changes.
Reviewer 2 Report
Comments and Suggestions for AuthorsI am satisfied with the answers provided by the authors and I think that this work is publishable in the present state.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors responded to my comments and made most of the suggested changes. Therefore, in accordance with the current version of the paper, they suggested to accept it for publication.
