Effect of Conventional and Microwave Heating on Protein and Odor Profile in Soymilk Powder
Round 1
Reviewer 1 Report
1. There is no theoretical justification for the power and duration of microwave exposure.
2. The dielectric properties of the processed material are not considered.
3. It is not clear which sources of microwave power were used.
4. It is not clear how the power of the microwave power source was regulated: different magnetrons were used, or the duty cycle changed when the same source was switched on pulsed.
5. It is not clear whether the field strength affects the efficiency of the process.
6. What are the maximum allowable concentrations of trypsin inhibitor?
7. The efficiency of the sources used in terms of energy efficiency or process productivity has not been considered.
8. It was worth considering the possibility of using IR heating in addition to microwave.
9. Conclusions should be formulated from the point of view of the goals and objectives of the study, as well as in setting the processing methods under consideration.
10. It was worth considering the works of S.O. Nelson on heating and processing of materials.
Author Response
Explanation on how the reviewers’ comments have been addressed in the revised manuscript
Manuscript ID: Sustainability-2526790
Title: Effect of conventional and microwave heating on protein and odor profile in soymilk powder
Thank you for all valuable advice from the reviewers. The manuscript has been revised as suggested.
Reviewer #1
- There is no theoretical justification for the power and duration of microwave exposure.
Author response: The experimental conditions of the microwave treatment were set from a preliminary study to obtain temperature of soymilk and processing time in the range of pasteurization, sterilization and UHT that had potential to inhibit Trypsin inhibitor [14]. This is for further study and application of microwave treatment for inhibition of microorganisms at different microwave power. These sentences were added into Page 3 Line 115-117.
- The dielectric properties of the processed material are not considered.
Author response: The dielectric properties of the soy milk has been reviewed from the previous studies. The dielectric constant (Ɛ՛) and loss factor (Ɛ՛՛) of soymilk (at 20-70 °C), were in the range of 60.3-73.0 and 8.0-18.1, respectively [20]. This sentence was added into Page 2 Line 72-75. The dielectric properties demonstrated high potential of soymilk to absorb the microwave energy and reasonably convert the absorbed energy into heat. Therefore, the microwave should be effectively used for treatment of soymilk. In this study, the soymilk was prepared from soybean without addition of food additives in the same batch and supposed to have the same composition. Therefore, all soymilk samples were assumed to have the same initial dielectric properties and similar to the dielectric properties of soymilk from literature reviews.
- It is not clear which sources of microwave power were used.
Author response: The microwave was operated at a frequency of 2450 MHz, with a magnetron to convert electrical energy into microwave energy. Then, the microwave energy was directly applied into the sample through a waveguide. In addition, a rotating plate was used to ensure even distribution of the microwave for the uniform heating. These sentences were added in Page 3 Line 117-119.
- It is not clear how the power of the microwave power source was regulated: different magnetrons were used, or the duty cycle changed when the same source was switched on pulsed.
Author response: The output power of microwave is manipulated by a controller. The controller controls the ON-OFF time of a relay to obtain the average output power at the setting condition. These sentences were added in Page 3 Line 119-122.
- It is not clear whether the field strength affects the efficiency of the process.
Author response: In this study, the field strength was kept as a constant parameter for all treatment condition.
- What are the maximum allowable concentrations of trypsin inhibitor?
Author response: The United States Food and Drug Administration (FDA) recommends manufacturers to reduce TI activity by at least 80%, for any residual activity to not interfere with the protease's ability for protein digestion or human health. In the case of soymilk, the initial trypsin inhibitor was 36.66 mg/g., thus the allowable concentrations of trypsin inhibitor should be less than 7.33 mg/g. These sentences were added in Page 9 Line 343-345.
- The efficiency of the sources used in terms of energy efficiency or process productivity has not been considered.
Author response: Thank you for pointing this issue. This study did not evaluate the process efficiency and productivity. It can be included as a part of our further study on optimization of microwave treatment. According to literature reviews, the microwave heating has been reported as one of the effective heating methods, in term of process efficiency and productivity.
- It was worth considering the possibility of using IR heating in addition to microwave.
Author response: Thank you very much for the valuable advice. We will consider including IR in our further experiment.
- Conclusions should be formulated from the point of view of the goals and objectives of the study, as well as in setting the processing methods under consideration.
Author response: Conclusions were revised as suggested. Please see Page14 Line 460-470.
- It was worth considering the works of S.O. Nelson on heating and processing of materials.
Author response: Thank you so much for your suggestion. The works of S.O. Nelson was added in the section ‘Introduction’ on Page 2 Line 69-72.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
1-W and temperature comparisons were made. It is not specified how many degrees 900 W is equivalent to temperature.
2-5 came after 3.5.
3-Why is 6 called a patent?
4-It could be a figure or a flowchart.
Author Response
Explanation on how the reviewers’ comments have been addressed in the revised manuscript
Manuscript ID: Sustainability-2526790
Title: Effect of conventional and microwave heating on protein and odor profile in soymilk powder
Thank you for all valuable advice from the reviewers. The manuscript has been revised as suggested.
Reviewer #2
1-W and temperature comparisons were made. It is not specified how many degrees 900 W is equivalent to temperature.
Author response: The experiment was controlled by the setting power at 360, 600 and 900 W. Then the consequent temperature of soymilk was measured. The conversion from microwave energy to heating temperature is not certain because. the generated heat is partially used for temperature rising and some is used for evaporation to change water to vapor. In addition, the conversion from the absorbed microwave energy to heat is also dependent of amount of water (dipolar molecule) in food. When evaporation is occurred, water content is decreased. Then the conversion from the microwave power to temperature is also changed. The maximum temperatures of all treatments were added into Table 1 to present variation of product temperatures from different treatment conditions.
2-5 came after 3.5.
Author response: The section number was revised to ‘4’ as suggested.
3-Why is 6 called a patent?
Author response: It is our mistake. The section ‘Patent’ was deleted..
4-It could be a figure or a flowchart.
Author response: It is our mistake. The section ‘Patent’ was deleted.
Author Response File: Author Response.pdf
Reviewer 3 Report
I congratulate each and every one of the authors who participated in the preparation of this article. From my point of view, this is a well-founded article and each and every one of its stages is well structured. I only had one question about the article and this is: How do you explain the fact that even though the trypsin inhibitor content in soy milk powder microwave treatment is much less than that found in conventionally heated soymilk, the protein digestibility of microwaved soymilk is much less than the protein digestibility conventionally heated is less than that found in conventionally heated soymilk
Comments for author File: Comments.pdf
I am not an expert in English language but the quality of English language used in this article is very fine.
Author Response
Explanation on how the reviewers’ comments have been addressed in the revised manuscript
Manuscript ID: Sustainability-2526790
Title: Effect of conventional and microwave heating on protein and odor profile in soymilk powder
Thank you for all valuable advice from the reviewers. The manuscript has been revised as suggested.
Reviewer #3
I congratulate each and every one of the authors who participated in the preparation of this article. From my point of view, this is a well-founded article and each and every one of its stages is well structured. I only had one question about the article and this is: How do you explain the fact that even though the trypsin inhibitor content in soy milk powder microwave treatment is much less than that found in conventionally heated soymilk, the protein digestibility of microwaved soymilk is much less than the protein digestibility conventionally heated soymilk?
Author response: Thank you very much for the positive comment.
The conventional heating at 100 °C for 20 min yielded significant improvements in protein digestibility, compared with the control. When the conventional heating was processed for a long time, it caused protein denaturation and a higher protein digestibility. For a much shorter time, microwave heating at 360W and 600W was enough to reduce trypsin inhibitor content in soy milk powder and its performance was more effective than the conventional heating. This was because microwave energy directly propagated through the soymilk and the absorbed energy was converted to heat [1]. However, to increase the degree of protein denaturation and thereby protein digestibility, a higher microwave power was required to modify and yield the looser structure. Therefore, the high microwave power at 900 W was recommended for both reduction of trypsin inhibitor and improvement of protein digestibility. The benefit of the proper microwave treatment on modification of protein structure was also reported by [2, 53].
In addition, all grammatical errors in the manuscript file were revised as suggested.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The work was done on a current topic. The use of electrophysical heating methods can be effective for a number of technological processes, including those discussed in the article. The authors made a sufficient review of existing studies and made appropriate references. However, there are a number of remarks that can be implemented in further research:
1. It is necessary to clearly justify the required energy for the implementation of heating. At the same time, it is worth considering the theoretical minimum of the required energy and the energy expended from various heating sources.
2. It is worth considering and justifying the required frequency of the microwave field for heating at the required rate and to the desired temperature.
3. It makes sense to consider various sources of energy for heating, since the depth of penetration of the field into the material largely depends on the frequency of the supply radiation.
4. To implement the technological process on an industrial scale, it is necessary to justify and formulate the thickness of the processed layer of material, the speed of its movement, etc.
5. Conclusions should be formulated more specifically, according to the goals and objectives of the study.
Author Response
Explanation on how the reviewer’ comments have been addressed in the revised manuscript
Manuscript ID: sustainability-2526790R1
Title: Effect of conventional and microwave heating on protein and odor profile in soymilk powder
Thank you for all valuable advice from the reviewers. The manuscript has been revised as suggested. Please see the response in blue parts.
Reviewer #1 (Round 2)
The work was done on a current topic. The use of electrophysical heating methods can be effective for a number of technological processes, including those discussed in the article. The authors made a sufficient review of existing studies and made appropriate references. However, there are a number of remarks that can be implemented in further research:
- It is necessary to clearly justify the required energy for the implementation of heating. At the same time, it is worth considering the theoretical minimum of the required energy and the energy expended from various heating sources.
Author response: Energy for the heating process was in the range of 0.006-0.167 kW.h. The information was added in Table 1.
- It is worth considering and justifying the required frequency of the microwave field for heating at the required rate and to the desired temperature.
Author response: In this study, the frequency of field was 2450 MHz. The desired temperature should be in the range of pasteurization (<100 0C), sterilization (>100 0C) and UHT (> 132 0C). More information of microwave operation was added in Page 3 Line 111-123 and Page 7 Line 310 and 317-319.
- It makes sense to consider various sources of energy for heating, since the depth of penetration of the field into the material largely depends on the frequency of the supply radiation.
Author response: Thank you for your valuable advice. In this study, only microwave with frequency of 2450 MHz was used to study its potential to improve nutritional availability of soymilk. In the next study, more sources of energy and frequency ranges will be determined to find the best solution for food sustainability.
- To implement the technological process on an industrial scale, it is necessary to justify and formulate the thickness of the processed layer of material, the speed of its movement, etc.
Author response: Thank you for valuable advice. This can be concerned for implementation. Some suggestion for implementation in an industrial process was added in Page 14 Line 481-484.
- Conclusions should be formulated more specifically, according to the goals and objectives of the study.
Author response: Conclusions were revised to be more specific as suggested. Please see Page14 Line 467-476.
Author Response File: Author Response.pdf
