Selection of a Proper Maturity Index for the Mechanical Harvesting of ‘Mihong’ Peach Fruit

Round 1

Reviewer 1 Report

Using Mihong’ peaches as material, the optimal maturity index through a quality survey were selected for the different DAFB. The findings show that color values are an outstanding non-destructive alternative to typical destructive measurements for determining the harvest time. It is valuable for the agricultural production. However, some questions should be responded or clarified as below:

1. Is this article just for finding the reliable parameters for harvest time? How the robot harvester can perception it precisely?

2. For peach fruits, the surface color is not heterogeneous.What is the consideration for this?

3. TA measurement, can the authors provide the reference for this method detail?

Author Response

Responses to the reviewer’s comments

General response

Dear Reviewers

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled ‘Selection of a proper maturity index for the mechanical harvesting of ‘Mihong’ peach fruit’ to MDPI Horticulturae. We appreciate the time and effort that you and the reviewers have dedicated to providing your valuable feedback on our manuscript. We are grateful to the reviewers for their insightful comments on our paper. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers.

Here is a point-by-point response to the reviewers’ comments and concerns.

Comments from Reviewer 1

1. Is this article just for finding the reliable parameters for harvest time? How the robot harvester can perception it precisely?

Response: Thank you for pointing this out. In our experiment, we determine the optimum maturity index for harvesting the ‘Mihong’ peaches by comparing different indices through a quality survey. This project consists of another team related to robot engineering. So, the mission of this study is to make a model by selecting the optimum maturity index for harvest prediction added to the robot through an algorithm developed by the programmer. In that manner, a robot harvester can percept it precisely and can be implemented for field usage. We think that we have not mentioned this clearly in the manuscript, so some details were added in lines 87-88 for a proper understanding.    

2. For peach fruits, the surface color is not heterogeneous. What is the consideration for this?

Response: Yes. We agree with the comment. Here we have taken the data over two years from the same Mihong trees in the same location. As well as here, we take an average value from the sample in both years. Furthermore, we measured the right and left side color values from the fruit and those measurements showed a similar pattern of variation. So, the heterogeneity of the color in the fruit surface has been minimized as much as possible.

3. TA measurement, can the authors provide the reference for this method in detail?

Response: We agree with this suggestion and have incorporated the reference to the text in the materials and method section in page 4, 154 line.

Reviewer 2 Report

This paper investigated the proper maturity index for the mechanical harvesting of ‘Mihong’ peach fruit. However, the experimental design has no novelty. Other experiments need to be supplemented. 

1.     Appearance of all samples during harvest days needs to be added.

2.     Respiratory rate of all samples during harvest days needs to be supplemented.

3.     What is the paper’s novelty? 

Some problelms are as follows:

1.     In Figure 3C, the ANOVA analysis of 2022 has some problem, please check the significance letter. It’s wrong.

2.     For all Figures, the axis X should show the DAFB, not date. Because the time of full bloom is affected by climate and environment.

3.     Some description in the results and discussion part has mistakes. Please check it.

Author Response

Responses to the reviewer’s comments

General response

Dear Reviewers

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled ‘Selection of a proper maturity index for the mechanical harvesting of ‘Mihong’ peach fruit’ to MDPI Horticulturae. We appreciate the time and effort that you and the reviewers have dedicated to providing your valuable feedback on our manuscript. We are grateful to the reviewers for their insightful comments on our paper. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers.

Here is a point-by-point response to the reviewers’ comments and concerns.

Comments from Reviewer 2

1. Appearance of all samples during harvest days needs to be added.

Response: Thank you for the suggestion. We have incorporated Figure 1 on page 3 to emphasize the appearance changes during the experiment.

2. Respiratory rate of all samples during harvest days needs to be supplemented.

Response: It would have been better to address this issue. However, in this experiment, we did not measure the respiration rate and only the ethylene production was measured in the 2022 year. The contribution of the measurements of respiration rate and ethylene production for deciding the exact harvesting date is significantly less compared to other parameters and we surely agree that it is important for understanding the ripening during the experiment time.

3. What is the paper’s novelty? 

Response: We appreciate you for figuring this out. Actually, this is the first time an optimal harvesting index has been determined for the 'Mihong' peach, for a mechanical harvesting approach that will employ a robot harvester. There is not much literature that was studied about the apex side color values in peaches for identifying the best maturity stage. In this study, we evaluated a variety of commonly used quality indicators, and among those measures, the most accurate and feasible technique was color values, specially a* values on the apex side. Based on the results of this study it will be incorporated into the robot harvester through an algorithm in order to percept it precisely and can be implemented for field usage.

Although there are several trending approaches, including NIR and hyperspectral, this one also can be utilized as a non-destructive, simple, precise, cost-effective and user-friendly method.    

4. In Figure 3C, the ANOVA analysis of 2022 has some problems, please check the significance letter. It’s wrong.

Response: We are so grateful for pointing out the mistake in the figure. Now it has been corrected accordingly.

5. For all Figures, the axis X should show the DAFB, not date. Because the time of full bloom is affected by climate and environment.

Response: We really appreciate this suggestion. It would have been interesting to explore this aspect. However, in the case of our study, it seems slightly difficult to understand the concept that we are going to express with the DAFB since there is a 7-day delay in the full bloom of the ‘Mihong’ peach in 2022 due to the weather and environmental conditions. At the very first we have graphed the parameters against the days after full bloom. But with that difference in time, it is difficult to understand and compare the results in two years for the reader. As well as when harvesting the fruit, we basically consider the maturity stage depending on the color on the apex side and other general parameters. Even though there is a delay in full bloom in 2022, the fruits have obtained the target maturity for first harvesting on the same day as 2021. It showed that the effect of days after full bloom is considerably less to the maturity of the ‘Mihong’ fruit. So, the harvesting date was represented the x-axis for better understanding and easy comparison.

6. Some description in the results and discussion part has mistakes. Please check it.

Response: We revise and correct all reviewer’s comments.

Reviewer 3 Report

Comment.

1.    In material and method, what are the criteria for choosing harvesting date in this study? It is the most important information in this study, please address those criteria.

2.    In material and method, in 2021 and in 2022, sample size was different (36 and 20 fruits each day). Please provide more reason why it is not the same.

3.    In section 2.2.4 soluble solid content, please provide information how to prepare sample for determination since it needs liquid form for SSC determination.

4.    In section 2.2.5 titratable acidity, how to prepare 1 mL pulp, please provide information.

5.    In Figure 2 and 3, what is 6.05 – 6.30 in X-axis? There is no information about this.

6.    It is not clear how each parameter in this study relates to the desired quality of peach. Discussion and explanation is required for this issue. Is it important to explain about consumer acceptance?

7.    Line 230, “they can reach acceptable flavor quality with minimum mechanical damage….” Any evidence for this claim since it is mentioned that it is from author’s study.

8.    Line 252-254, “suggested that……is the ideal period to harvest peach…” how to get this conclusion? Please provide more explanation.

9.    Line 311-325, Please provide more information about “chroma” and “hue” and how these values are important in quality determination.

10. In Table 1 and 2, please add SD or SE.

Author Response

Responses to the reviewer’s comments

General response

Dear Reviewers

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled ‘Selection of a proper maturity index for the mechanical harvesting of ‘Mihong’ peach fruit’ to MDPI Horticulturae. We appreciate the time and effort that you and the reviewers have dedicated to providing your valuable feedback on our manuscript. We are grateful to the reviewers for their insightful comments on our paper. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers.

Here is a point-by-point response to the reviewers’ comments and concerns.

Comments from Reviewer 3

1. In material and method, what are the criteria for choosing the harvesting date in this study? It is the most important information in this study, please address those criteria.

Response: We agree with this suggestion and have amended this in detail in the materials and methodology section in lines 97-99. The harvesting date was selected basically by studying the apex side color values in the fruit and in addition to that we consider the general parameters such as overall color development and fruit size by measuring the length and width of the fruit and whether it has accompanied the considerable size for harvesting.

2. In material and method, in 2021 and in 2022, the sample size was different (36 and 20 fruits each day). Please provide more reasons why it is not the same.

Response: We considered this suggestion and this has now been emphasized in the section on materials and methods, in lines 103-105. There were variations in fruiting capacity because of the weather and environmental factors. Therefore, in 2022, the fruit load was lower than in 2021. The sample size had to be lowered to 20 fruits as we continued the experiment through a period of 7 days and we had to choose the fruits in equivalent sizes, similar conditions, and similar maturation stages for the consistency of the experiment.

3. In section 2.2.4 soluble solid content, please provide information how to prepare sample for determination since it needs liquid form for SSC determination.

Response: We agree with this suggestion and now we have revised the content adding some more details to the text in materials and method on 141-143 lines.

4. In section 2.2.5 titratable acidity, how to prepare 1 mL pulp, please provide information.

Response: We have adjusted the content with further details and references in the method 2.2.5 section on 152-154 lines according to the reviewer’s suggestion.

5. In Figure 2 and 3, what is 6.05 – 6.30 in X-axis? There is no information about this.

Response: We have expressed the harvest date from the x-axis starting from June 5 to June 30. It has been mentioned in Table 1 and Table 2 in the original manuscript with the days after full bloom (DAFB). But maybe we have not made this sufficiently clear. So, for more details, it is as follows.

6. It is not clear how each parameter in this study relates to the desired quality of peach. Discussion and explanation is required for this issue. Is it important to explain about consumer acceptance?

Response: We agree with this suggestion and some points were amended as the reviewer mentioned.

The optimum fruit size varies mainly depending on the cultivar; we have mentioned that June 20 yields desired size with stone formation since it has passed the second phase of the peach double sigmoid growth curve.

The ideal SSC range for peach fruit is around 11 Brix°, according to the literature cited (Tomás-Barberán et al., 2001, Drogoudi et al., 2016, Petruccelli, 2023). We think that this has been already mentioned in the original manuscript on lines 210-211 and added some more references on lines 212-217.

We cannot mention an exact firmness range that will match the consumer preference. But if the firmness is very low fruits can easily damage and post-harvest losses can happen. If the firmness is lower than 5N it is significantly softer. So, handling is very difficult and obviously mechanical harvesting cannot be performed. Firmness around 20N is possible for machine harvesting since it has a significant value. But the fruits should be getting softer during the distribution time for good eating quality.  

When considering the TA content with the fruit maturity acid content should be reduced and the lower the acid content, the better the flavor. The literature has reported TA values of 0.13–0.31% in white-fleshed peaches and 0.45–0.87% in yellow-fleshed peaches; or a range from 0.15–0.34% in white peaches and from 0.53–0.97% in yellow-flesh peaches, and, 0.31–0.47% in white peaches and from 0.53 to 0.86% in yellow peaches has optimum eating quality (Petruccelli, 2023). Some more details were added into the text with more references regarding the TA in results and discussion section in lines 261-265.

Color is a key factor in determining fruit maturity, and appearance is the first factor evaluated at harvest. Regarding the color values L*, a*, b*, chroma, and hue, more details were mentioned in the text in the section of 3.3. These values may differ depending on the cultivar (Petruccelli, 2023). So, for ‘Mihong’ peach the most important a* value should be higher than 0 value in order to harvest at least on the apex side. Positive a* values showed the red color development. If the a* value is around 15 on apex side it can be considered the optimum stage with the evidence of other SSC, firmness and TA values.

Considering the ethylene production, it is unable to express an exact value for optimum maturity since many physical factors and handling can affect to the rate of ethylene production. However higher the ethylene production, the higher the maturation and ripening. 

Refernces:

Drogoudi, P et al., 2016. The appraisal of qualitative parameters and antioxidant contents during postharvest peach fruit ripening underlines the genotype significance. Postharvest Biology and Technology, 115, 142-150.

Petruccelli, R et al., 2023. Evaluation of the Fruit Quality and Phytochemical Compounds in Peach and Nectarine Cultivars. MDPI Plants, 12.

Tomás-Barberán, F. A et al., 2001. HPLC− DAD− ESIMS analysis of phenolic compounds in nectarines, peaches, and plums. Journal of Agricultural and Food Chemistry, 49, 4748-4760.

7. Line 230, “they can reach acceptable flavor quality with minimum mechanical damage….” Any evidence for this claim since it is mentioned that it is from author’s study.

Response: We think that it has been discussed it in the 3.2 section, but maybe we have not made this sufficiently clear.

SSC responsible for mostly for the flavor since it corresponds to the sugar content. By June 20, fruits have accomplished the 8 °Brix of SSC and if we harvest the fruits at this stage within two or three days (during the distribution time) these fruits can reach to the 11 °Brix which is considered as the acceptance SSC for consumption (provided more literature as a response to the 6^th comment). After this date all other SSC measurements also showed the maximum amount around 11 °Brix. That means there is no any significant increment in SSC which means the sweetness or the flavor of the fruits.

The firmness responsible for mainly on handling process as well as softness of the fruit. At this stage firmness is higher (around 20N) compared to last date. But they can obtain the softness as last dates within two days (during distribution time).

And when it comes to the TA value it is also around 0.3-0.4% which has a lower acid content favorable for consumer (provided literature as a response to the 6^th comment).

After June 20 fruits have the almost similar quality parameters. But with ripening, softness will increase and it limit the most handling practices. As well as it takes some time to distribute to the market. So, if we harvest more lately the fruits may ended up with the over maturity. That is why here we have mentioned June 20 is the optimum time for harvesting since it already achieved favorable fruit quality and handling is also possible without less damage.     

8. Line 252-254, “suggested that……is the ideal period to harvest peach…” how to get this conclusion? Please provide more explanation.

Response: We think that the above response has addressed this issue regarding the reason for this conclusion. Since we can harvest fruits with good quality and less damage it can be considered as the ideal period to harvest ‘Mihong’ peach. 

9. Line 311-325, Please provide more information about “chroma” and “hue” and how these values are important in quality determination.

Response: We agree with this suggestion and now it has been provided more details with references on page 11 in lines 340-342 and 348-351.

10. In Table 1 and 2, please add SD or SE.

Response: We appreciate this suggestion and now Table 1 and 2 have been modified with SE values and revised in 3.3 section in results and discussion on page 12-13.

Round 2

Reviewer 1 Report

Most comments have been accepted and adjusted positively. However, the format of reference list is not uniform. Please check the No. 1, 12, 24, 37, 39, etc. The capitalization in the title are not consistent with others. 

Author Response

Responses to the reviewer’s comments

General response

Dear Reviewers

Thank you for reviewing our revised draft of the manuscript titled ‘Selection of a proper maturity index for the mechanical harvesting of ‘Mihong’ peach fruit’ to MDPI Horticulturae. We appreciate the time and effort that you and the reviewers have dedicated to providing your valuable feedback on our manuscript. We are grateful to the reviewers for their insightful comments on our paper. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers.

Here is a point-by-point response to the reviewers’ comments and concerns.

Comments from Reviewer 1

Most comments have been accepted and adjusted positively. However, the format of the reference list is not uniform. Please check the No. 1, 12, 24, 37, 39, etc. The capitalization in the title is not consistent with others. 

Response: We are really grateful for pointing out the issue in the reference part. Now all references have been corrected as the reviewer mentioned.

We appreciate your valuable comments.

Reviewer 2 Report

The authors replied most of all questions, but there still some problems needed to be revised.

In the Abstract, authors described samples were collected on different days after full bloom (71 to 90 in 2021, 64 to 84 in 2022), but the result just showed the day such as June 20. The day after full bloom is more scientific than the detailed day, year. So the authors should give the day after full bloom in the result. It’s more understandable.

Figure 1 showed the different maturity stages of ‘Mihong’ peaches in 2022. Samples collected on different days in 2021 should be given together. So it can be easily to compare the appearance of all samples on different days.

Author Response

Responses to the reviewer’s comments

General response

Dear Reviewers

Thank you for reviewing our revised draft of the manuscript titled ‘Selection of a proper maturity index for the mechanical harvesting of ‘Mihong’ peach fruit’ to MDPI Horticulturae. We appreciate the time and effort that you and the reviewers have dedicated to providing your valuable feedback on our manuscript. We are grateful to the reviewers for their insightful comments on our paper. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers.

Here is a point-by-point response to the reviewers’ comments and concerns.

Comments from Reviewer 2

The authors replied most of all questions, but there still some problems needed to be revised.

In the Abstract, authors described samples were collected on different days after full bloom (71 to 90 in 2021, 64 to 84 in 2022), but the result just showed the day such as June 20. The day after full bloom is more scientific than the detailed day, year. So, the authors should give the day after full bloom in the result. It’s more understandable.

Response: We agree with the reviewer’s suggestion. Since there is a significant time gap between the DAFB of two years, we thought that if we mentioned the DAFB in the x-axis in the graphs it may mislead the reader regarding the maturity. Because the maturity at the harvesting date was identical in two years while considering the other characteristics, despite the DAFB. Therefore, we included graphs with both DAFB and harvest date utilizing as the x-axis in order to provide a clearer understanding.

Figure 1 showed the different maturity stages of ‘Mihong’ peaches in 2022. Samples collected on different days in 2021 should be given together. So, it can be easily to compare the appearance of all samples on different days.

Response: We appreciate the reviewer’s suggestion. So, now we have added an image of peaches at different harvesting dates in 2021 sample into the Figure 1 as a combination.

We appreciate your valuable comments.

Reviewer 3 Report

It can be accepted for publication in the present form.

Author Response

Responses to the reviewer’s comments

General response

Dear Reviewers

Thank you for reviewing our revised draft of the manuscript titled ‘Selection of a proper maturity index for the mechanical harvesting of ‘Mihong’ peach fruit’ to MDPI Horticulturae. We appreciate the time and effort that you and the reviewers have dedicated to providing your valuable feedback on our manuscript. We are grateful to the reviewers for their insightful comments on our paper. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewers.

Here is a point-by-point response to the reviewers’ comments and concerns.

Comments from Reviewer 3

It can be accepted for publication in the present form.

Response: We appreciate your valuable comments. Thanks again.