Review Reports - Improvement of the Potato Protein Drying Process as an Example of Implementing Sustainable Development in Industry

Round 1

Reviewer 1 Report (Previous Reviewer 1)

Comments and Suggestions for Authors

Self-citations that raised ethical issues have been removed from the manuscript. A significant number of useful references have been added, the text of the manuscript has been significantly reworked, which has improved the article. A solution to a particular problem has been presented that can be demonstrated to the global scientific community. The article can be published.

Author Response

Dear Sir,

Thank you very much for your review which allowed us to improve the manuscript. Thank you very much for the acceptation of the changes that we made following your suggestions.

Reviewer 2 Report (Previous Reviewer 3)

Comments and Suggestions for Authors

Journal Name: Sustainability

Manuscript Number: sustainability-3762460

Title: Improvement of the potato protein drying process as an example of implementing the sustainable development in industry

Comments to the author

The Introduction should include quantitative descriptions of the energy consumption status of potato protein drying processes.

While the current Introduction (lines 34-90) mentions the high energy consumption of drying processes (e.g., lines 87-89 note that drying accounts for 12-20% of industrial energy demand), it lacks specific data supporting the potato protein drying sector. The authors are advised to supplement the paper with data on the energy consumption proportion of this process in the food industry, energy efficiency benchmarks of existing technologies (e.g., energy consumption per unit product in kWh/kg), or comparative energy consumption data with other protein drying technologies (e.g., soy protein) to strengthen the practical significance of the research question.

The Methods section needs to clarify key design parameters of the heat recovery system.

In Section 2.3 (lines 176-254), when describing the heat recovery system, the authors do not provide details on the performance parameters of core equipment (e.g., heat exchange efficiency, pressure drop of the Klingenberg heat exchanger) and system integration details (e.g., pipeline insulation measures). It is suggested to add:

(1) The basis for heat exchanger selection (e.g., logarithmic mean temperature difference under design conditions);

(2) Quantitative indicators of system energy efficiency improvement (e.g., calculation formula for heat recovery rate);

(3) Control strategies (e.g., accuracy and response time of temperature sensors) to ensure the reproducibility of the experiments.

The Results and Discussion section needs to deepen the analysis of economic and environmental benefits.

Section 3 (lines 256-312) provides heat recovery data (e.g., lines 307-309 mention recovery of 806 kW + 2000 kW) but does not translate it into actual benefits. It is recommended to:

(1) Calculate annual energy-saving benefits (e.g., amount of steam saved × local energy price);

(2) Assess carbon emission reductions (e.g., calculate CO₂ emission reduction in tons based on IPCC coefficients);

(3) Compare the payback period of the investment (requiring data on equipment retrofit costs) to align with the practical orientation of circular economy research required by the Sustainability journal.

Comments for author File: Comments.pdf

Author Response

Dear Sir,

Thank you very much for your review and suggestions of changes which allowed us to improve the submitted manuscript.

The Introduction should include quantitative descriptions of the energy consumption status of potato protein drying processes.

We add the required information following your suggestions in the text of Introduction.

For the described solution, prior to modernization, the heat demand was approximately 2800 kWh, which, at a protein production rate of 850 kg/h, resulted in a heat demand of 3.29 kWh/kg of potato protein at 20% moisture. Due to the specific nature of the food industry and the process solutions used during drying, it is extremely difficult to compare the described solution and its heat demand with other solutions used, for example, in the drying of soy protein. Soy protein is dried using spray drying, while potato protein is dried in air dryers.

The Methods section needs to clarify key design parameters of the heat recovery system.

(1) The basis for heat exchanger selection (e.g., logarithmic mean temperature difference under design conditions);

(2) Quantitative indicators of system energy efficiency improvement (e.g., calculation formula for heat recovery rate);

(3) Control strategies (e.g., accuracy and response time of temperature sensors) to ensure the reproducibility of the experiments.

A table with basic operating parameters (technical and operational data) has been added. The basic operating parameters of the exchanger are given in Table 2.

Table 2. Nominal technical and operational data of the heat exchanger.

		Air supply	Air exhaust
Inlet	Standard flow, m³/h	42000	55000
	Workflow, m³/h	40530	69206
	Temperature, C	10	95.0
	Relative humidity, %	75.0	2.0
	Absolute humidity, g/kg	5.70	10.56
	Enthalpy, kJ/kg	24.4	124.3
Outlet	Workflow, m³/h	48669	61076
	Temperature, C	66.9	51.8
	Relative humidity, %	3.4	12.6
	Absolute humidity, g/kg	5.70	10.56
	Enthalpy, kJ/kg	82.4	79.6
Air velocity – inlet, m/s		1.88	3.20
Pressure drop, Pa		148	272
Pressure drop for normal density, Pa		137	225
Dry exchange efficiency, %		66.9	50.9
Wet exchange efficiency, %		66.9	50.9
Dry heat recovery, kW		806.63	-806.63
Wet heat recovery, kW		806.63	-806.63

The Results and Discussion section needs to deepen the analysis of economic and environmental benefits.

Section 3 (lines 256-312) provides heat recovery data (e.g., lines 307-309 mention recovery of 806 kW + 2000 kW) but does not translate it into actual benefits. It is recommended to:

(1) Calculate annual energy-saving benefits (e.g., amount of steam saved × local energy price);

(2) Assess carbon emission reductions (e.g., calculate CO₂ emission reduction in tons based on IPCC coefficients);

Considering the above, the benefits of using an energy recovery system for the modernized process line are as follows:

Improved energy efficiency of the protein dryer:

- before modernization: 2800 kWh / 850 kg/h = 3.29 kWh / 1 kg of protein,

- after modernization and recovery of ~806 kWh of heat, the energy efficiency is 2000 kWh / 850 kg/h = 2.35 kWh / 1 kg of protein, reducing the energy input by ~28%.

Improved energy efficiency of the starch dryer:

- before modernization: heat demand: 5950 kWh / 15800 kg of starch (2 x 190 tons/day / 24 hours = 15800 kg) = 0.38 kWh / 1 kg of starch with 20% moisture,

- after modernization: 5950 kWh – 2000 kWh = 3950kWh / 158000kg = 0.25kWh/1kg of starch, energy consumption reduced by ~ 34%

These are, of course, production savings resulting from the reduction in the demand for thermal energy to produce 1 kg of protein or potato starch.

However, environmental savings are also crucial. The heat source is a coal-fired boiler producing steam at 12 bar. This translates to savings of 2,800 kW for each hour of operation of the process line.

Assuming the average calorific value of hard coal, the equivalent of 2,800 kW of thermal energy per hour (800 kW for a protein dryer and 2,000 kW for a starch dryer), and assuming that 1 kg of hard coal (medium quality) provides 4-5 kW of energy, for each hour of operation of the technological line we burn 560 to 700 kg less coal. For a 2,400-hour potato campaign, the savings in solid fuel range from 1,344,000 to 1,680,000 kg, or 1,344 to 1,680 tons, respectively.

The above results enable the reduction of CO₂ content from coal combustion in the range from 3252.5 to 4065.6 tonnes of CO₂

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

The comments are placed in the attachement.

Comments for author File: Comments.pdf

Author Response

Dear Sir,

Thank you very much for your review and suggestions for changes that allowed us to improve the submitted paper.

The format of the manuscript is particularly poor, and it is still in revision mode. It must be modified carefully.

Thank you for your attention to the article's format. We have endeavored to prepare the manuscript in accordance with the editor's requirements.

The formatting of citations in the reference section is inconsistent (e.g., References 12, 28, 43).

Thank you, we corrected the references format in this section.

In the Materials and Methods section, it is mentioned that the temperature measurement time is fixed at 7:00 a.m. Could this choice of time affect the representativeness of the temperature data? In addition, the initially assumed ambient temperature of 10°C was not recorded during the measurement. Could this deviation affect the accuracy of the energy calculation results?

The measurement of the external ambient temperature and its changes are not significant for the calculation methodology, but it should also be noted that this is not a research installation operating under constant conditions; it is a working industrial installation, and certain calculated values are assumed constant. An ambient temperature of 10°C was assumed as a starting parameter for equipment selection, bearing in mind that this parameter changes throughout the potato campaign. At the installation's location and for the production duration during the potato campaign (September–December), the assumed 10°C is the average air temperature, determined by institutions providing weather parameters.

It is mentioned in the paper that "there are not many examples in the literature that document the redesign of existing production lines". However, no further analysis has been provided on the specific manifestations of the research gap in this field. It is recommended to supplement a comparative analysis of relevant industrial application cases in the past five years to highlight the innovativeness and necessity of this research.

The scientific literature is insufficient on changes in production line design because the confidentiality clauses required in the companies where they are applied. The scientific literature presents changes regarding processes and their parameters, but not specific solutions that impact company development and economics. In this article, we describe the changes introduced to demonstrate trends in the current development directions of manufacturing companies according to the sustainable development.

Figures 1, 2, 3, and 4, as key process schematics, only label the names of equipment and measuring points. Could the flow direction and flow rate information of materials be clearly marked in the figures? In addition, some parameters in Tables 1, 2, and 3 do not specify the standardized writing of units, which may lead to ambiguous understanding among readers. It is recommended to correct them and add necessary annotations.

Thank you, we prepared the figures again adding the required details.

Round 2

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

Accept in present form

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The introduction should cite general literature - monographs, review or the closest manuscript (prototypes) on the research topic. The authors cited works 4 and 8, which are self-citations and can be regarded as inappropriate. There is no reference in the text to reference 4 (see line 33).

The proposed technical solution may be of interest to food industry technologists or scientists involved in the processing of agricultural raw materials. The presented material can be considered from the point of view of increasing production efficiency, as a solution to an important, but small and private problem.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors:

Your MS could be interesting, but there are many things to add to achieve this goal. Here are some recommendations.

The abstract must show the novelty and the new findings because when you read it, it does not include the main aspects of your MS. Even the title must be re-adapted because your article is about potato protein but the title does not include this information.

It is necessary to have a schematic diagram for materials and methods because every phase of your experimental work is unclear. It is also important to have references supporting your methodology. Please add references regarding this subject.

Do you have any statistical information? This is always important to validate your results. Please add statistical measurements, ANOVA, or any design of experiments.

Your discussion needs to be strengthened, so please add scientific literature to compare your results according to every step of the new schematic diagram of your methodology.

The conclusions must include the new findings, the novelty of your study, and the gaps because it is very "general", it is necessary to modify it to have relevant information.

Reviewer 3 Report

Comments and Suggestions for Authors

Comments to the author

Abstract

1. Add a description of the research background in the first sentence of the abstract.

2. Authors should depict a brief explanation about the necessity of carrying out such study?

3. Can you provide a detailed explanation of the significant economic and environmental benefits, which is in line with the circular economy and has brought about significant economic and environmental benefits?

Introduction

1. The paper’s theoretical contributions are limited, failing to propose new theoretical viewpoints or models.

2. There are no research questions clearly delineated and no discussion how author is going to address these research questions.

3. what’s the research gap and objectiveness?

4. The introduction mentions that circular economy is an innovative resource and production management model, emphasizing sustainable development. In the food industry, besides the utilization of waste heat mentioned in the article, what other common innovative technologies or models are in line with the concept of circular economy? Has there been a comparative analysis of these in the article?

5.This paper points out that the drying process is one of the most important unit operations in food processing, and it is a complex multiphase and multi physical process. When studying the physical and chemical changes during the drying process, besides the strategies mentioned in the article such as optimizing energy consumption and using renewable energy, what other new research directions or technological means are currently being explored to further improve the efficiency and quality of the drying process?

Materials and Methods

1. The numbering of Section 2 is actually written as Section 3, which resulted in incorrect numbering of subsequent Sections.

2. In section 2.1, it is mentioned that potato protein is obtained from potato cell sap through hot acid coagulation, dehydration, and drying. Its protein content and amino acid composition have high nutritional value. May I ask if the extraction and drying process of potato protein is mature in actual production? Are there any cases of large-scale industrial production? Has the article analyzed the advantages and disadvantages of existing processes?

2. Section 2.2 describes the principle and parameters of the dryer before the renovation. May I ask if it is necessary to adjust the parameters of this traditional convection dryer, which is widely used in the field of food drying, when drying different types of food? Are these parameters mentioned in the article applicable to all types of food drying, or only for potato protein?

3. Section 2.3 elaborates on the concept of modernizing the dryer. How to ensure that the transformed system can seamlessly integrate with the original production line during the implementation of the transformation, without affecting the continuity and stability of the overall production process? Did the article mention any relevant transitional measures or technical means?

Research and discussion

1. Has the waste heat utilization method proposed in the article taken into account the changes in waste heat sources under different seasons and production loads in practical applications? How to ensure effective recovery and utilization of waste heat under various working conditions?

2. The article analyzed the effectiveness of waste heat recovery through data from temperature measurement points. May I ask if the selection of these measurement points is representative? Can it fully reflect the performance of the entire waste heat recovery system? How to ensure the accuracy and stability of the data from these measurement points in actual operation?

3. The results showed that through the renovation, the temperature of the air discharged from the dryer was significantly reduced, and the waste heat was effectively recovered. Does this modification have an impact on the drying efficiency and product quality of the dryer? Have relevant comparative experiments or data analysis been conducted to prove that the quality of the modified product still meets the requirements?

Conclusions

1. The conclusion mentions that the proposed waste heat utilization solution is an example of circular economy and can be extended to other production plants. May I ask how to make customized adjustments and optimizations based on the specific situation of different factories during the promotion process? Does the article provide some general guiding principles or methods?

2. The final energy-saving effect mentioned in the conclusion depends on various factors, such as the degree of production mechanization, equipment technology status, etc. Has the article provided a detailed analysis and evaluation of these factors? How to effectively control and improve these factors in actual production to maximize the energy-saving benefits of waste heat utilization systems?

3. What are the research limitations and future research directions of the paper?

In summary, I believe that the paper needs major revisions.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

This manuscript's English is generally comprehensible but needs refinement.