Novel Energy-Saving Strategies in Apple Storage: A Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Authors focused on the analyzes of different storage technologies aiming to reduce energy consumption such as 1-methylcyclopropene, ultra-low oxygen and dynamic controlled atmosphere together with raised temperatures. The integration of advanced monitoring and control systems, coupled with data analytics and energy management in apple storage was also discussed. These sustainable strategies could be implemented without cost-intensive construction measures in standard storage facilities. Furthermore, beneficial side effects of higher storage temperatures in terms of a reduced occurrence of storage disorder symptoms and higher maintenance of quality attributes were also discussed for this special issue on sustainable horticultural production systems and supply chains. The subject matter is extremely important nowadays, as it enhances green innovation performance and helps to minimize negative impact on the environment.

 

Comments and Suggestions for Authors

·         Line 41: Lack of space between coma and 2.

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·         Line 315: Table 2: Lack of space between comas and references numbers.

·         If the energy consumption was counted is it possible to calculate a carbon footprint (CF)? The article would gain interest in a wider readership, since CF is a popular determinant of environmental impact.

 

Author Response

first of all thanks for your suggestions, we appreciate them a lot.

Line 41: Lack of space between coma and 2.

Line 47: Lack of space between coma and 5.

Line 53: Lack of space between coma and 10.

Line 61: Lack of space between coma and 13.

Line 72: Lack of space between coma and 9 and 10.

Line 82: Lack of space between coma and 17.

Line 91: Lack of space between coma and 19.

Line 93: Lack of space between coma and 20.

Line 158: Lack of space between coma and 23.

Line 160: Lack of space between coma and 29 and 30.

Line 163: Lack of space between coma and 30.

Line 173: Lack of space between coma and 36.

Line 184: Lack of space between coma and 38.

Line 271: Lack of space between coma and 32 and 52.

Line 280: Lack of space between coma and 32.

Line 315: Table 2: Lack of space between comas and references numbers.

 

Response: The references are formatted according to the guidelines of ‘Sustainability’, which do not specify space between numbers.

 

If the energy consumption was counted is it possible to calculate a carbon footprint (CF)? The article would gain interest in a wider readership, since CF is a popular determinant of environmental impact.

 

Response: Thank you for this suggestion, we initially considered including a calculated carbon footprint in the review as well as an estimation of how much money could potentially be saved.  However, the studies we reviewed were conducted in different countries and under varying circumstances. Most of the cited works stated no information about the initial energy source of the storage facilities and the refrigeration systems. We therefore concluded that any calculation or rough estimation of a CF for each respective study would be imprecise as too many assumptions would have to be made. We faced similar challenges when attempting to estimate money savings, given the great difference in electricity prices depending on the country and the energy source.

In conclusion, the decision was made to focus strictly on the comparison of the total energy usage in each study respectively storage strategy.

Reviewer 2 Report

Comments and Suggestions for Authors

The energy-saving strategies in apple fruit storage is important, but there are still some problems in this article:

（1）I think that there was no direct relationship between the market prices and electricity costs，What is the significance of Figure 1?

Figure 1：Average apple market prices and electricity costs in the Lake Constance Region in Southern Germany

（2）I think that the maximum storage period of different method is more important than the energy savings，Please add the maximum storage period in Table 1

（3）Besides the energy savings, the costs of other methods（1-methylcyclopropene, ultra-low oxygen and dynamic controlled atmosphere together with raised temperatures）should be considered in the results.

(4) You should discuss the benefits and risks of the energy-efficient form（1-methylcyclopropene, ultra-low oxygen and dynamic controlled atmosphere together with raised temperatures）.

(5) Whether there is the latest research about the energy-efficient form of apple storaging, most of the literature are older(such as 24, 25, ).

(6) The energy savings [%] in table 1,  I don’t know whether it is accurate or not.

(7) You provide the most energy-efficient storage methods for the main apple varieties in this paper based on the different storage period.

Comments on the Quality of English Language

Minor editing of English language required

Author Response

I think that there was no direct relationship between the market prices and electricity costs，What is the significance of Figure 1?

The fact that there is no direct relationship between the market prices that growers receive for the stored and sold apples and the electricity costs for storage is precisely the point we were trying to make. Energy prices have increased substantially over the past decade. If this had been accompanied by an increase in revenue due to increasing apple prices, this circumstance would present less of a problem. However, apple prices did not increase comparatively. Therefore, novel approaches to reduce energy usage and therefore costs of storage are essential. This circumstance was described in the text to justify the research conducted in this field as well as the review put together.

I think that the maximum storage period of different method is more important than the energy savings. Please add the maximum storage period in Table 1

We respectfully disagree. This review is written about strategies to reduce energy usage during storage, so this information is vital. The storage lengths of each experiment have been added to Table 1. However, it is important to acknowledge that these were just the storage durations of these experiments and not necessarily the possible maximum storage period that the reviewer was referring to.

Besides the energy savings, the costs of other methods（1-methylcyclopropene, ultra-low oxygen and dynamic controlled atmosphere together with raised temperatures）should be considered in the results.

The additional costs of 1-MCP applications have been addressed in the manuscript. The review focused on showing that 1-MCP applications allow to increase the storage temperatures without accelerating the quality deterioration of the fruit. There are multiple 1-MCP products available on the market so it is difficult to make a universal statement about the costs of application. Prices may also differ between countries. As mentioned in the manuscript, before pursuing the high temperature + 1-MCP approach it must be made sure depending on the market situation and the situation in the market facility, that the application is financially sensible. We believe the manuscript shows that 1-MCP application does not only provide benefits in terms of energy savings but also superior fruit conservation and reduced postharvest losses.

A sentence has been added to the manuscript to reflect the potentially additional energy costs of ULO and DCA storage. Increasing or dynamically adjusting the temperature does not cause additional costs, in fact, it contributes to reducing costs.

Whether there is the latest research about the energy-efficient form of apple storaging, most of the literature are older(such as 24, 25, ).

Energy savings in storage is a major focus of postharvest research at the moment, however, this manuscript had a very specific focus. An extensive literature search has been conducted and to our knowledge, all works on the interaction of 1-MCP and increased storage temperatures in saving energy while maintaining apple fruit quality, have been included in this work.

We recognize that some of the cited studies are more than 10 years old. However, in our opinion, this should not adversely affect the validity of the results. Newer studies from 2015 [27] and 2022 [28] agree with these earlier findings and show that this is still an effective approach for the commercial fruit storage sector. To our knowledge, at least in southern Germany, 1-MCP + higher storage temperature is despite these promising results not a common practice yet which justifies the review put together. Most studies on DCA technologies are from recent years 2017-2023.

You should discuss the benefits and risks of the energy-efficient form（1-methylcyclopropene, ultra-low oxygen and dynamic controlled atmosphere together with raised temperatures）.

The benefits of improved quality conservation and reduced incidences of disorder symptoms are discussed throughout the manuscript for the combination of raised temperatures and 1-MCP or ULO/DCA.

The risks and drawbacks of 1-MCP application are addressed in the final paragraph of section 2. When taking cultivar-specific sensitivities to atmospheric conditions into account, the establishment of  ULO conditions does not necessarily mean a higher risk than a standard CA storage system. Furthermore, it could actually be argued that DCA storage, if executed correctly, reduces the risks of damage to the fruit material as oxygen stress signals are continuously monitored. A sentence has been added to stress the importance of setting the atmospheric conditions according to the individual apple cultivar’s requirements.

The energy savings [%] in table 1,  I don’t know whether it is accurate or not.

As this is a review of already published and peer-reviewed studies, we trust the validity of the results.

You provide the most energy-efficient storage methods for the main apple varieties in this paper based on the different storage period.

Thank you for reviewing this manuscript

Reviewer 3 Report

Comments and Suggestions for Authors

 

Büchele et al. summarize the novel energy-saving strategies in apple fruit storage in this review. The authors compared different storage technologies, such as 1-methylcyclopropene, ultra-low oxygen, dynamically controlled atmosphere, and elevated temperatures, to reduce energy consumption. They discussed integrating advanced monitoring and control systems, data analytics, and energy management. Furthermore, they also discussed the beneficial side effects of higher storage temperatures in terms of reduced occurrence of storage disorder symptoms and more significant maintenance of quality attributes.

General comments:

This is an interesting review; the authors have collected a valuable dataset of interest. The manuscript is generally clear and structured. The study's conclusions are supported by appropriate evidence; the claims are not exaggerated.

The manuscript is an adequate, engaging novel, interesting, and suitable for publication after minor language revisions.

 

Comments on the Quality of English Language

Revisions:

Line 39: temperatures – temperature

Line 44: full – whole

Line 55: , similar - ; similar

Line 59: exhibit – exhibits

Line 61: load – loads

Line 64: is therefore, - is, therefore

Line 65: crucial – , it is crucial

Line 70: face the competition – compete with

Line 82: energy-saving

Line 93: contributing – contribute

Line 95: elevated – an elevated

Line 96: the application of – applying; ultra-low

Line 113: full – entire

Line 147: It was furthermore shown – Furthermore, it showed

Line 173: affects – affects

Line 185: cover – covers

Line 213: damages – damage

Line 255: have - has

 

Author Response

first of all thanks for your suggestions, we appreciate them a lot.

 Comments on the Quality of English Language

Revisions:

Line 39: temperatures – temperature

Line 44: full – whole

Line 55: , similar - ; similar

Line 59: exhibit – exhibits

Line 61: load – loads

Line 64: is therefore, - is, therefore

Line 65: crucial – , it is crucial

Line 70: face the competition – compete with

Line 82: energy-saving

Line 93: contributing – contribute

Line 95: elevated – an elevated

Line 96: the application of – applying; ultra-low

Line 113: full – entire

Line 147: It was furthermore shown – Furthermore, it showed

Line 173: affects – affects

Line 185: cover – covers

Line 213: damages – damage

Line 255: have - has 

Thank you for your language corrections, all have been included with the exception of line 147, 185 and 255.

Fruit can also be the plural form, so “have” would be correct in this instance. 

Reviewer 4 Report

Comments and Suggestions for Authors

Novel energy-saving strategies in apple fruit storage holding a manuscript number of 2772848 is a review work on different storage technologies of apple to reduce energy consumption and more focusing on the use of 1-methylcyclopropene, ultra-low oxygen and dynamic controlled atmosphere along with the use of advanced monitoring and controlling systems, coupled with data analysis and energy management. The manuscript is well written with clear description of each section giving a strategic conclusion. I have only few minor comments:

1.      Please omit the term ‘fruit’ from title – “Novel energy-saving strategies in apple storage: A review” or “A review on novel energy-saving strategies in apple storage”.

2.      Please define SDG 12.

Author Response

first of all thanks for your suggestions, we appreciate them a lot.

1. Please omit the term ‘fruit’ from title – “Novel energy-saving strategies in apple storage: A review” or “A review on novel energy-saving strategies in apple storage”.

Thank you for this suggestion. The first title is used now.

2. Please define SDG 12.

SDG is now defined in the manuscript.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The questions of the reviewer were answered，agree to be received.

Comments on the Quality of English Language

Minor editing of English language required