Microgreens: Optimising Seed Density and Exploring the Influence of White Light and White Light Supplemented with UV-A Radiation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The body of research on microgreens is relatively recent and limited. In this manuscript presents data on the impact of seeding density on the yield and total microbial load of microgreens from three different crops. These data will contribute to the understanding of the microbial risk during the cultivation and consumption of these crops under controlled growing conditions. I would like to make the following comments regarding the manuscript:

1. The title of the article does not reflect its content. The manuscript does not present data on changes in harvest time depending on seed density and light spectrum. It is recommended to change the title to more accurately reflect the main objective and the results obtained.
2. Indicate clearly the objective of the study in the abstract.
3. The abstract does not contain specific data on the impact of UV-A exposure on yield and microbial load. I believe that it is necessary to mention this is because the assessment of the influence of light spectrum is indicated in the title of the manuscript and is part of the objectives of the study.
4. Please improve the introduction. The introduction needs to be revised to omit redundant information, particularly regarding seed density. The introduction should be supplemented with the most recent works in literature about related to bacterial and fungal load during microgreen cultivation. At the end of the introduction, the main purpose of the study can be improved by avoiding the results obtained.
5. Table 2 does not contain the results of statistical data processing. Use some statistical test to compare means.
6. The following sentences are provided in the sections Abstract and Conclusions: Lines 24-25 «...continuous UV-A exposure did not sustain higher phytochemical levels or reduce microbial load compared with white light» and Lines 434-435 «Prolonged exposure to UV-A light did not maintain increased phytochemical levels or lower the microbial load», while the discussion section states: Lines 401-402 «Furthermore, our findings showed significant differences in microbial load of pea microgreens grown under white and UV-A light». This contradiction should be explained.

Author Response

1. Summary
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.
Reviewer 1
Comments 1: The title of the article does not reflect its content. The manuscript does not present data on changes in harvest time depending on seed density and light spectrum. It is recommended to change the title to more accurately reflect the main objective and the results obtained.
Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have modified the title of the article (Highlighted in red in the manuscript and below) “Microgreens: Optimising seed density and exploring the influence of white light and white light supplemented with UV-A radiation.”
Comments 2: Indicate clearly the objective of the study in the abstract. Response 2: Agree. We have, accordingly, revised the abstract to emphasise the objective of the study. Changes can be found on Page 1, lines 13-16 (Highlighted in red)
Comments 3: The abstract does not contain specific data on the impact of UV-A exposure on yield and microbial load. I believe that it is necessary to mention this is because the assessment of the influence of light spectrum is indicated in the title of the manuscript and is part of the objectives of the study.   Response 3: Agree, we have added results from UV-A light exposure on Page 1, lines 22-27.

 

 

 

Comments 4: Please improve the introduction. The introduction needs to be revised to omit redundant information, particularly regarding seed density. The introduction should be supplemented with the most recent works in literature about related to bacterial and fungal load during microgreen cultivation. At the end of the introduction, the main purpose of the study can be improved by avoiding the results obtained.

Response 4: Thank you for pointing this out. Added more recent studies that can be found on Page 3, lines 108-114 and 116-120 highlighted in red.

We have removed lines as following (62-64, 68-73, 77-79, 80-82 and 83-85) from Page 2 to streamline the introduction.

 

Comments 5: Table 2 does not contain the results of statistical data processing. Use some statistical test to compare means.

   

Response 5: Agree, I have added statistical results in Table 2 Page 7-8.

 

Comments 6: The following sentences are provided in the sections Abstract and Conclusions: Lines 24-25 «...continuous UV-A exposure did not sustain higher phytochemical levels or reduce microbial load compared with white light» and Lines 434-435 «Prolonged exposure to UV-A light did not maintain increased phytochemical levels or lower the microbial load», while the discussion section states: Lines 401-402 «Furthermore, our findings showed significant differences in microbial load of pea microgreens grown under white and UV-A light». This contradiction should be explained.

 

Response 6: We thank the reviewer for noting this contradiction. The significant differences in microbial load were observed only at specific time points and were not sustained over the growing period; therefore, UV-A did not produce a consistent long-term reduction compared with white light. The Discussion has been revised accordingly to clarify this point.

Changes are highlighted in red on Page 13 lines 438-440

 

 

 

Additional clarifications

We appreciate your time and valuable feedback. In addition, we have made further revisions to the Materials and Methods section to provide more detailed information about the experimental setup.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript reports a case study experiment on the effect of seed density and optical radiation spectrum on microgreens harvesting time. The manuscript is well-structured, and the measurement protocols are described. However, I find some methodological weaknesses, and therefore I suggest a major revision.

My most important comments:

1. No explicit randomization procedure is described; it is not clear whether environmental conditions (airflow, temperature etc.) were controlled during the experiment.
2. No information on the PPFD values for both compared conditions – were the PPFDs maintained constant and the same for both experimental regimes? What was the PPD value in µmol/(m²·s)? Although “UV‑A light” composition (33% near‑UV at 365 nm + 66% cool white) is reported, it is not clear what the percentages mean. The reproducibility of the experiment is also limited, which prevents comparison with other studies. The term “white light” is used without providing the spectral distribution. Although the CCT remains the same, the light spectrum may differ, which would strongly affect microgreen physiology. The uniformity of illumination across the shelves was not reported. In my opinion, without this information, it is not possible to evaluate the correctness of the results and conclusions.
3. I suggest not to use „ultraviolet light” – according to the definitions (e.g. CIE lighting vocabulary or Electropedia) light is radiation enclosed within the visible range. Therefore, I suggest using “UV radiation”.
4. I suggest proofreading due to some minor typos in the bodytext.

Author Response

1. Summary
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Reviewer 2

 

 

Comments 1: No explicit randomization procedure is described; it is not clear whether environmental conditions (airflow, temperature etc.) were controlled during the experiment.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have added more information about experimental setup and randomization in the methods section, Page 4-5, lines 147-153 and 170-171 indicated in red. We have also added an experimental setup in Figure 1, Page 5 with details of average daily temperature and humidity.

Comments 2: No information on the PPFD values for both compared conditions – were the PPFDs maintained constant and the same for both experimental regimes? What was the PPD value in µmol/(m²·s)? Although “UV‑A light” composition (33% near‑UV at 365 nm + 66% cool white) is reported, it is not clear what the percentages mean. The reproducibility of the experiment is also limited, which prevents comparison with other studies. The term “white light” is used without providing the spectral distribution. Although the CCT remains the same, the light spectrum may differ, which would strongly affect microgreen physiology. The uniformity of illumination across the shelves was not reported. In my opinion, without this information, it is not possible to evaluate the correctness of the results and conclusions.

Response 2: We thank the reviewer for emphasising the importance of reporting PPFD. Direct PPFD measurements were not recorded during the experiment because the study utilised commercially specified LED fixtures with manufacturer-reported photon flux values and recommended operating distances. The lights were installed according to these specifications to ensure consistent light delivery across treatments. Importantly, both experimental conditions used the same base white LED system, and the UV-A treatment functioned solely as a supplemental light source. Therefore, the PAR component driving photosynthesis was comparable between treatments, allowing valid assessment of the UV-A effect. However, we have mentioned approx PPFD in the material and methods (given in the manufacture’s datasheet) in Page 4, line 144 and Page 5 line, 188-190. We have also added an experimental image page 5 to provide more information to readers.   For UV-A light composition, out of all photons emitted by the lamp, one-third are UV-A while two-thirds are broad-spectrum white photons.   Comments 3: I suggest not to use „ultraviolet light” – according to the definitions (e.g. CIE lighting vocabulary or Electropedia) light is radiation enclosed within the visible range. Therefore, I suggest using “UV radiation”.   Response 3: Thank you for pointing this out. We have replaced it with white light supplemented with UV-A radiation (highlighted in red).   Comments 4: I suggest proofreading due to some minor typos in the bodytext.

Response 4: We have carefully proofread the manuscript and correct the minor typos in the body text accordingly.

 

 

 

 

 

 

 

 

 

 

 

 

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for the revision of the manuscript. Considering no measurement data for the light and UV irradiance, I would expect providing the light distribution curves from the manufacturers of the lamps (if available). The data on the distance and the size of the growing areas would also be beneficial as well as the mounting height of the lamps. That would allow other researchers to replicate the experimental conditions (to some extent). The best possible solution would be adding information on the PPFD values.

For the future experiments I strongly recommend performing the PPFD measurements.  

Author Response

1. Summary
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Reviewer 2

Comments 1: Considering no measurement data for the light and UV irradiance, I would expect providing the light distribution curves from the manufacturers of the lamps (if available).

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have added a spectrogram as per the manufacturer’s datasheet. Changes can be found in Figure 1 a), page 5. Highlighted in yellow.

Comments 2: The data on the distance and the size of the growing areas would also be beneficial as well as the mounting height of the lamps.

Response 2: We thank the reviewer for emphasising on distance and area. We have added more information. Changes can be found in lines 145-146 and 157, Page 4. Highlighted in yellow.   Comments 3: That would allow other researchers to replicate the experimental conditions (to some extent). The best possible solution would be adding information on the PPFD values.   Response 3: Thank you for this important suggestion. Although PPFD was not directly measured during the experiment, we have now included the approximate PPFD values reported in the manufacturer’s datasheet in the Materials and Methods section to improve reproducibility, lines 145, I 91-192, Page 4-5.

Author Response File: Author Response.docx