Over-the-Row Mechanical Harvest of Cider Apples (Malus domestica Borkh.)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript describes multiple apple harvesting experiments conducted using an improved Oxbo-Korvan 930 harvester. Indicators including fruit removal rate, fruit leakage rate, branch breakage rate, harvesting time, and harvesting efficiency were measured. The authors compared the efficiency of mechanical harvesting to that of manual harvesting, as well as the time required to harvest all fruits from an entire tree via mechanical means versus manual means. Additionally, the juice quality of mechanically harvested apples was tested. The work carried out by the authors holds certain significance for apple harvesting practices.

However, the approach used to investigate the phenomena addressed in this paper is occasionally unclear. Major revisions are required before the manuscript can be reconsidered for publication.

1. The "Materials and Methods" section lacks detailed experimental protocols and testing procedures. Additionally, the experimental design is unreasonable, and essential data analysis for the indicators is missing.
2. In lines 20–31, the fruit removal rate and harvesting time of the improved Oxbo-Korvan 930 are compared with those of manual harvesting. However, relevant data for the original Oxbo-Korvan 930 is lacking for comparison, making it impossible to determine whether the improved version has higher harvesting efficiency. Furthermore, the entire paper does not mention the fruit damage rate or the extent of fruit injury during harvesting. It is suggested that the authors provide an explanation for this.
3. In line 108 of the "Materials and Methods" section, the test indicators and their corresponding calculation methods are missing. It is suggested that the authors supplement this information and explain each indicator and method separately.
4. In line 127, the improvements made to the Oxbo-Korvan 930 only involve increasing the size of the prototype based on the original design. Has the original Oxbo-Korvan 930 prototype undergone corresponding apple harvesting experiments? Moreover, the article does not detail the relevant motion parameters and operating parameters of the improved Oxbo-Korvan 930 during the harvesting process. It is suggested that the authors provide an explanation for these omissions.
5. The text states that damage to apples caused by mechanical harvesting has a relatively minor impact on juice production. However, in Figure 1, when fruits fall onto the collection plate below the harvester and are subsequently transported to the fruit box, significant bruising occurs due to collisions and contact. It is unclear whether this level of bruising can be ignored, and it is suggested that the authors provide an explanation.
6. In line 249, the question arises: does the removal of spurs with fruits per tree during mechanical harvesting have any impact on fruit quality? Additionally, would the breaking of fruit branches during mechanical harvesting affect the subsequent fruit yield and quality of the trees? If these factors have no impact, it is recommended that the authors delete all irrelevant indicators (including other unrelated parameters) throughout the text.
7. In line 294 (referring to Table 4), the juice quality (e.g., TSS, SG, etc.) of apples harvested by the improved Oxbo-Korvan 930 prototype is analyzed. However, no comparison is made with the juice quality of manually harvested apples, making it impossible to evaluate the quality of juice obtained via mechanical harvesting. It is suggested that the authors provide an explanation for this lack of comparison.
8. In the "Discussion" section, the authors extensively explore the influence of individual factors on single outcomes. However, the conclusions lack logical connections, and the discussion itself is rather disorganized. It is recommended that the authors present their explanations in a hierarchical and structured manner.

Author Response

The work carried out by the authors holds certain significance for apple harvesting practices.

However, the approach used to investigate the phenomena addressed in this paper is occasionally unclear. Major revisions are required before the manuscript can be reconsidered for publication.

 

1. The "Materials and Methods" section lacks detailed experimental protocols and testing procedures. Additionally, the experimental design is unreasonable, and essential data analysis for the indicators is missing

Response: The Materials and Methods section is detailed and complete. The research orchard was planted in an RCBD and thus this is the design of this experiment. This is a reasonable experimental design for orchard research in general. Data analysis methods have been expanded to provide more details, L195-199.

 

2. L 20–31 fruit removal rate and harvesting time of the improved Oxbo-Korvan 930 are compared with those of manual harvesting. However, relevant data for the original Oxbo-Korvan 930 is lacking for comparison, making it impossible to determine whether the improved version has higher harvesting efficiency. Furthermore, the entire paper does not mention the fruit damage rate or the extent of fruit injury during harvesting. It is suggested that the authors provide an explanation for this.

Response: the Oxbo-Korvan 930 used in this study was built to harvest Jatropha (Jatropha curcas) and it was not ‘improved’, it was modified to harvest tree fruit only by increasing the tunnel height and we have emphasized this L104-105. We included supplemental information that describes the purpose for the original Oxbo-Korvan 930. Fruit bruising is acknowledged L226 and lacerations L226-229. Juice quality, which is a major concerning outcome of damaged fruit, is discussed L229-237.

 

3. In line 108 of the "Materials and Methods" section, the test indicators and their corresponding calculation methods are missing. It is suggested that the authors supplement this information and explain each indicator and method separately.

Response: It is unclear what test indicators and calculation methods the reviewer is referring to. We revised methods based on explicit feedback from other reviewers, which should address this comment.

 

4. L 127, the improvements made to the Oxbo-Korvan 930 only involve increasing the size of the prototype based on the original design. Has the original Oxbo-Korvan 930 prototype undergone corresponding apple harvesting experiments? Moreover, the article does not detail the relevant motion parameters and operating parameters of the improved Oxbo-Korvan 930 during the harvesting process. It is suggested that the authors provide an explanation for these omissions.

Response: the Oxbo-Korvan 930 used in this study was not ‘improved’ it was modified to harvest tree fruit only by increasing the tunnel height; we have emphasized this L104-105. The original Oxbo-Korvan 930 was built to harvest Jatropha (Jatropha curcas) and has not been used for apple harvest, see supplemental information.  Note that we had included the supplemental information in our submission but it appears this section was not included for reviewers. We included more details regarding the harvester, L107-111.  

 

5. The text states that damage to apples caused by mechanical harvesting has a relatively minor impact on juice production. However, in Figure 1, when fruits fall onto the collection plate below the harvester and are subsequently transported to the fruit box, significant bruising occurs due to collisions and contact. It is unclear whether this level of bruising can be ignored, and it is suggested that the authors provide an explanation.

Response: Fruit bruising is acknowledged L226 and lacerations L226-229. Juice quality, which is a major concerning outcome of damaged fruit, is discussed L229-237. No changes were made to the manuscript.

 

6. In line 249, the question arises: does the removal of spurs with fruits per tree during mechanical harvesting have any impact on fruit quality? Additionally, would the breaking of fruit branches during mechanical harvesting affect the subsequent fruit yield and quality of the trees? If these factors have no impact, it is recommended that the authors delete all irrelevant indicators (including other unrelated parameters) throughout the text.

Response: It is uncertain if spur removal and branch breakage have long-term impacts on orchard yield and tree health. While there did not appear to be any affects in our 3-year experiment, these impacts should be acknowledged so future research can determine if there are any negative long-term impacts. Assessing tree health was added to the Conclusion L332.

 

7. In line 294 (referring to Table 4), the juice quality (e.g., TSS, SG, etc.) of apples harvested by the improved Oxbo-Korvan 930 prototype is analyzed. However, no comparison is made with the juice quality of manually harvested apples, making it impossible to evaluate the quality of juice obtained via mechanical harvesting. It is suggested that the authors provide an explanation for this lack of comparison.

Response: Table 3 (there is no Table 4) presents juice quality within 3 days of harvest and after 15-35 days of cold storage. First, the question is if mechanically harvested fruit will lose quality due to storage, and second, other studies have compared juice quality of hand harvest and over-the-row harvested fruit and found no differences. We added the first point to our study objectives L86-88.

 

8. In the "Discussion" section, the authors extensively explore the influence of individual factors on single outcomes. However, the conclusions lack logical connections, and the discussion itself is rather disorganized. It is recommended that the authors present their explanations in a hierarchical and structured manner.

Response: We have shortened sections of the Discussion to address this concern: spur removal L 300-302; branch breakage L302-304; tannins L310-313.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents valuable research on the application of an over-the-row mechanical harvester for cider apples, supported by multi-year field trials and detailed measurements of harvest efficiency, tree damage, and juice quality. The topic is relevant and timely, and the work has the potential to make a meaningful contribution to the horticultural and cider apple production literature. However, several areas require further clarification, reorganization, and refinement to enhance the overall clarity and rigor of the paper.

 

1. In the introduction, the section on shake-and-sweep systems takes up a disproportionate share of the background. While relevant, it could be condensed to highlight more clearly the novelty of the over-the-row approach.

 

2. Methodology descriptions are generally clear, but the rationale behind cultivar selection in different years requires further explanation to improve transparency.

 

3. Details of the modifications made to the Oxbo-Korvan 930 are insufficient. Since these changes are central to the study, more technical information would help readers understand and reproduce the work.

 

4. Statistical analysis is only briefly outlined; clarification of model assumptions and the handling of repeated measures across years and cultivars would strengthen the rigor of the results.

 

5. Interpretation of results could be expanded. For example, the correlations between fruit size and laceration deserve deeper discussion regarding implications for storage and processing.

 

6. Conclusions remain too general. A stronger emphasis on orchard management, cultivar suitability, and potential economic implications would make the findings more impactful.

 

7. References show inconsistencies in formatting that should be corrected according to journal style.

Author Response

The manuscript presents valuable research on the application of an over-the-row mechanical harvester for cider apples, supported by multi-year field trials and detailed measurements of harvest efficiency, tree damage, and juice quality. The topic is relevant and timely, and the work has the potential to make a meaningful contribution to the horticultural and cider apple production literature. However, several areas require further clarification, reorganization, and refinement to enhance the overall clarity and rigor of the paper.

 

1. In the introduction, the section on shake-and-sweep systems takes up a disproportionate share of the background. While relevant, it could be condensed to highlight more clearly the novelty of the over-the-row approach.

 Response: We have condensed the section on shake-and-sweep harvesters, L64-68.

 

2. Methodology descriptions are generally clear, but the rationale behind cultivar selection in different years requires further explanation to improve transparency.

 Response: We revised the Methods description for how cultivars were selected for inclusion in the study, L118-122.

 

3. Details of the modifications made to the Oxbo-Korvan 930 are insufficient. Since these changes are central to the study, more technical information would help readers understand and reproduce the work.

 Response: Only the tunnel height was modified on the harvester, and this has been emphasized L104-105. We included more details regarding the harvester, L105-111.

 

4. Statistical analysis is only briefly outlined; clarification of model assumptions and the handling of repeated measures across years and cultivars would strengthen the rigor of the results.

 Response: Data analysis methods have been expanded to provide more details, L195-200.

 

5. Interpretation of results could be expanded. For example, the correlations between fruit size and laceration deserve deeper discussion regarding implications for storage and processing.

 Response: Results from our study indicate there were no negative impacts of fruit damage (bruising and lacerations) on fruit quality, both within 3 days of harvest and after 15-35 days cold storage. Thus there is no reason to expand this section, and no changes were made to the manuscript.

 

6. Conclusions remain too general. A stronger emphasis on orchard management, cultivar suitability, and potential economic implications would make the findings more impactful.

 Response: We have revised the Conclusions to provide more recommendations per the reviewer’s suggestions, L320-331.

 

7. References show inconsistencies in formatting that should be corrected according to journal style.

Response: We have revised reference formatting to meet journal style.

Reviewer 3 Report

Comments and Suggestions for Authors

1.L49-96: In recent years, significant progress has been made in orchard mechanized harvesting technologies, including pneumatic, robotic, and shaking-type harvesters. The article presents the advantages and significance of this study well. However, the review of existing research is not sufficiently clear. It is recommended to enrich the introduction and references.

2.L120-123: In Section 2.1, the authors describe the operating scenario, but the explanation is not clear enough. It is suggested to present it in the form of figures to enhance readability.

3.L125-132: In Section 2.2, the description of the mechanical harvester structure is not sufficiently clear. It is recommended to provide detailed figures showing different parts of the machine and to introduce the harvesting mechanism more explicitly. The operating parameters of the harvester should be presented in a table, with emphasis on the specifications of the end effector, such as the dimensions, material, and rotational speed of the harvesting rods.

4.L136: The experimental procedure is overly lengthy. Too much text is spent on operations unrelated to the core focus of the study, such as spraying plant growth regulators. It is suggested to emphasize the key aspects such as mechanical harvest efficiency and tree damage rate. In addition, the language is overly colloquial in some places; more academic phrasing is recommended.

5.L220: Table 1 only shows the harvest dates of different cultivars, but it does not highlight the main objectives of this study. It is recommended that the authors include key target parameters after mechanical harvesting of different cultivars in the table.

6.L260-273: Although the data in the results section is relatively complete, the experimental processes are insufficiently described. For example, the procedures and parameter settings for titratable acidity and soluble solids measurements are missing. It is recommended to add these details in the Materials and Methods section.

7.L313-382: The discussion and conclusion should be presented separately. In the discussion, it is recommended to further compare the findings with domestic and international research, and to identify the next research directions by weighing the advantages and disadvantages. For instance, improving harvesting efficiency and reducing fruit left on the tree or dropped on the ground through optimization of mechanical devices or control systems. The conclusion should be concise, summarizing the key findings of this study.

8.L389: The references are too few and most of them are outdated, lacking citations from the past three years. It is recommended to supplement with recent high-quality research in the relevant field.

Author Response

1.L49-96: In recent years, significant progress has been made in orchard mechanized harvesting technologies, including pneumatic, robotic, and shaking-type harvesters. The article presents the advantages and significance of this study well. However, the review of existing research is not sufficiently clear. It is recommended to enrich the introduction and references.

Response: While significant advances in mechanical harvesting technology have been made, they are not relevant for cider apples. The biggest potential advancement in cider apple harvest is the over-the-row harvester utilized in this study. Per the request of other reviewers to reduce information on other harvest methods and focus on the over-the-row technology in the Introduction, we will not expand this section to include technologies not utilized in cider apples. 

 

2.L120-123: In Section 2.1, the authors describe the operating scenario, but the explanation is not clear enough. It is suggested to present it in the form of figures to enhance readability.

Response: We have condensed to include only information relevant to the study (per other reviewer’s comments) and to provide clarity L96-102.

 

3.L125-132: In Section 2.2, the description of the mechanical harvester structure is not sufficiently clear. It is recommended to provide detailed figures showing different parts of the machine and to introduce the harvesting mechanism more explicitly. The operating parameters of the harvester should be presented in a table, with emphasis on the specifications of the end effector, such as the dimensions, material, and rotational speed of the harvesting rods.

Response: We have clarified that only one modification was made to the Oxbo-Korvan 930 harvester used in this study L104-105. The harvester otherwise is the standard equipment offered for sale by the company and all specifics can easily be found online. Therefore we did not include this information in our manuscript. We did add harvester rod type and size L109-111. Note that we included Supplemental Information that provides more information about the harvester we used.  

 

4.L136: The experimental procedure is overly lengthy. Too much text is spent on operations unrelated to the core focus of the study, such as spraying plant growth regulators. It is suggested to emphasize the key aspects such as mechanical harvest efficiency and tree damage rate. In addition, the language is overly colloquial in some places; more academic phrasing is recommended.

Response: We have reduced and refined the Methods section, specifically PGR L126-131, harvest methods L136-143, fruit handling post-harvest L144-148, fruit data post-harvest L154-160.

 

5.L220: Table 1 only shows the harvest dates of different cultivars, but it does not highlight the main objectives of this study. It is recommended that the authors include key target parameters after mechanical harvesting of different cultivars in the table.

Response: Table 1 reflects the primary study objective, which was to test a diversity of cider apple cultivars for mechanical over-the-row harvest. A main consideration for inclusion in the study was harvest date L118-119, as cultivars are grown in the same row and so harvest must occur at the same time for all cultivars. We did not add information to Table 1.

 

6.L260-273: Although the data in the results section is relatively complete, the experimental processes are insufficiently described. For example, the procedures and parameter settings for titratable acidity and soluble solids measurements are missing. It is recommended to add these details in the Materials and Methods section.

Response: The Methods describing juice analysis are adequate: TSS (Brix) L166-169, pH L169-171, TA L171-175, SG L175-177, tannins L177-184. No changes were made.

 

7.L313-382: The discussion and conclusion should be presented separately. In the discussion, it is recommended to further compare the findings with domestic and international research, and to identify the next research directions by weighing the advantages and disadvantages. For instance, improving harvesting efficiency and reducing fruit left on the tree or dropped on the ground through optimization of mechanical devices or control systems. The conclusion should be concise, summarizing the key findings of this study.

Response: We divided Discussion and Conclusion sections. In the Discussion we focused on the findings specific to our study as recommended by other reviewers. In the Conclusion we focused on primary findings from our study (i.e., improving harvester efficiency) and recommendations for future research L332-337.

 

8.L389: The references are too few and most of them are outdated, lacking citations from the past three years. It is recommended to supplement with recent high-quality research in the relevant field.

Response: Our manuscript is focused on over-the-row harvest of cider apples and we have included every published paper on this topic to date to the best of our knowledge. Of the 27 references that we have included, 8 are prior to 2014, 10 are 2015-2019, and 9 are 2020-2025. Historic references are included as they provide the foundational science (i.e., Lowenthal method, cider apple history). No changes were made to references.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The work conducted by the authors holds certain significance for apple harvesting practices. However, the approach adopted to investigate the phenomena addressed in this paper remains unclear. Major revisions are required before the manuscript can be reconsidered for publication. Below are my concerns:

1. The "Materials and Methods" section lacks detailed test measurement indicators. Please refer to other scientific papers in this journal for classified explanations of "Experimental Procedures"—for example, the paper titled "Nutritional Quality and Evaluation of Chinese Water Chestnuts from Different Origins."
2. The juice quality (e.g., TSS, SG, etc.) of apples harvested by the modified Oxbo-Korvan 930 prototype is analyzed in Table 4. However, no comparison is made with the juice quality of manually harvested apples, making it impossible to evaluate the quality of juice obtained via mechanical harvesting. Although the authors noted that other studies have compared the juice quality of hand-harvested and over-the-row harvested fruit and found no differences, this finding does not apply to harvesting with this specific prototype. It is suggested that the authors provide an explanation for this lack of comparison.
3. The conclusion section lacks quantitative conclusive statements. For instance: What is the efficiency of mechanized harvesting? How many times higher is it compared to manual harvesting? What changes occurred in the juice detection indicators presented in Table 3? Instead of focusing on discussing the reasons behind these outcomes, it is recommended that the authors rephrase the content to include such quantitative details.
4. The harvesting efficiency mentioned in the abstract is 82%, while the conclusion states that a simple improvement could increase this efficiency to over 90%. Whether such a "simple improvement" has undergone relevant harvesting tests or is merely a future-oriented prediction, it is recommended that the authors explain and clarify this point before asserting the efficiency improvement.

Author Response

1.  The "Materials and Methods" section lacks detailed test measurement indicators. Please refer to other scientific papers in this journal for classified explanations of "Experimental Procedures"—for example, the paper titled "Nutritional Quality and Evaluation of Chinese Water Chestnuts from Different Origins."

Response: The focus of our manuscript is not on cider apple juice quality post-harvest with the over-the-row harvester, but the suitability for this modified harvester to remove and capture fruit from cider apple trees and the impact of post-harvest cold storage on fruit loss and quality. We added L88-90 to clarify study goals. We added the milling and pressing equipment, subsample size, and temperature of freezer to the Methods L158-161. We added a statement to clarify the purpose of juice quality analysis was to assess if mechanically harvested fruit retained quality in cold storage L162-163. The methods provided for juice analysis in our manuscript are adequate and sufficient to convey to the reader what was done and how, and are reproducible, no further changes have been made to the Methods regarding juice analysis.

2.  The juice quality (e.g., TSS, SG, etc.) of apples harvested by the modified Oxbo-Korvan 930 prototype is analyzed in Table 4. However, no comparison is made with the juice quality of manually harvested apples, making it impossible to evaluate the quality of juice obtained via mechanical harvesting. Although the authors noted that other studies have compared the juice quality of hand-harvested and over-the-row harvested fruit and found no differences, this finding does not apply to harvesting with this specific prototype. It is suggested that the authors provide an explanation for this lack of comparison.

Response: We revised L59-60 to clarify that mechanical harvest is the norm for cider apples in Europe; thus we do not feel there is a need to compare quality of mechanically harvested and hand-harvested fruit. We added L62-63 to clarify the shake-and-sweep harvest system indiscriminately picks up apples from the orchard floor, including fruit that is very poor quality; and we added L71 to emphasize poor quality fruit is harvested with the current predominant mechanical harvest system. Our previous revision clarified that the objective for analyzing juice of mechanically harvested apples in this study was to determine if quality changed due to cold storage, and we have emphasized this again L88-90 and L162-163. We added L90-93 to clarify that the harvester used in the current study has the same mechanical harvest system (drum, rods, catch plates) as the harvester used in cited work that found no difference between mechanically harvested fruit and hand-harvested fruit.

3.  The conclusion section lacks quantitative conclusive statements. For instance: What is the efficiency of mechanized harvesting? How many times higher is it compared to manual harvesting? What changes occurred in the juice detection indicators presented in Table 3? Instead of focusing on discussing the reasons behind these outcomes, it is recommended that the authors rephrase the content to include such quantitative details.

Response: In the Conclusions we added a quantitative statement regarding harvest time efficiency L326-327. We also added a quantitative statement regarding fruit loss in storage due to rot and impact on juice quality L335-337.

4.  The harvesting efficiency mentioned in the abstract is 82%, while the conclusion states that a simple improvement could increase this efficiency to over 90%. Whether such a "simple improvement" has undergone relevant harvesting tests or is merely a future-oriented prediction, it is recommended that the authors explain and clarify this point before asserting the efficiency improvement.

Response: We clarified that all fruit lost from the harvester were lost at the front of the harvester and this loss would be reduced by our proposed adjustments L330-332. Proposed simple adjustments have been made for blueberry harvesters that have the same harvester technology as the harvester we tested in our study L333-335.

Reviewer 3 Report

Comments and Suggestions for Authors

I have no further comments.

Author Response

Response: Methods have been revised as described in response to Reviewer 1.