Centrifugal Filter-Assisted Block Freeze Crystallization Applied to Blueberry Juice
Round 1
Reviewer 1 Report
General comments
The manuscript reports about a method to separate the liquid produced during thawing of frozen juice from the (solid) ice fraction by gravitation or centrifugal forces. The phase separation was modified by adding a filter and retaining the solid (ice) fraction on the filter. Thus, the liquid's contact time on the solid phase is different from the three different separation techniques. The solute yield (liquid phase removed) is higher when phase separation is improved by adding a filter to the system. Interestingly, this is also true for the concentration of bioactive compounds or colourants in the solute (liquid phase). The different quantities (separated) and concentrations do not explain via the fraction of thawed material, as the heat transfer rate in the thawing-separation phase is supposed to be the same.
The difference should be related to different diffusion processes (an aspect not considered by the authors). At least the contact time between the liquid and the solid phase is supposed to be different (shorter for centrifuged and by a filter separated phases). In conclusion, the solute migration from high (liquid) to low (residual solid) concentration might be responsible for the observation. It is supposed that such an aspect must be involved in the scientific approach for a journal in chemical engineering. Besides, no information is available about the freezing process (e.g. the freezing rate influences the quality of the phase separation in freezing and freezing point of the residual non-frozen part of the substance). The final statement in the conclusions that "the addition of the filter allows a better separation of solution from the ice fraction" is trivial. "Better" stands for a higher concentration of the solution, but do not consider other aspects as the TRL or maintenance and manufacturing costs with filter centrifuges.
Another issue is the not explained difference between a much higher increase in the values such as TBC and TSS in centrifugal-filter BFC compared to the reference and the concentrate percentage of 80%. The concentration factor in a composition is not merrily explainable with the ratio of concentrate to ice (8:2).
Specific comments
Summary
L16: Please compare initial to final concentration.
L 18: The given numbers for TBC, AA and yield art not so easy to combine with the information on the process background (spread on different sentences). In the results section, other abbreviations are used (GBFC, CBFC, centrifugal-filter BFC). Consider a harmonization and using for each of the processes an abbreviation.
L23: there is no indication about the difference in the efficiency of TBC or AA retention between centrifugal filter assisted BFC and the other separation technics. Thus, the conclusion, "this research offers new benefits …" is not traceable at this stage of reading. Only the influence of "time" was explained in summary. Also, consider saying that technology offers this advantage instead of the research as such.
L23-26: Consider splitting the sentence and improving the readability.
Introduction
L31-37: The generic comments are relatively stand-alone, and the references do not prove a link between them. Avoid creating or overuse such links or specifications with words such as "every day", "thus", or "therefore", "thereby", "however", "hence" etc.
L38: What means "traditional concentration technologies" (= thermal)? And what the authors mean when saying that these technologies "has been evolved" (lower temperature, lower pressure?).
L42: Be more specific when reporting about the deterioration of nutritional properties. Sugar is also a nutrient, for example.
L43: Why the authors differentiate between "novel" and "emerging."
L47: "... increase … the extraction efficiency, percentage recovery … of nutritional … characteristics" is not a valid statement. What is the difference between "extraction efficiency" and "percentage of recovery"? Consider rephrasing.
L43-45: The term treatment should be used for all technologies in the list or non.
L49-50: "Non-thermal" and "low temperature" seem to be expressions that say the same.
L51: Total freezing of water in a solution is not possible. Total freezing of water and subsequent separation of unfrozen is not precise and would not be the right description of the process.
L54: Complete freezing of the liquid solution is impossible. Also, it should be partial thawing of the frozen solution before separation from the still frozen part.
L59: What the authors mean precisely with "natural thawing"?
L61: The authors merge thermal (MW) and mechanical (centrifugation) processes and classify both processes where external forces are applied. Please clarify and be specific with the use of terms. Driving forces of a process might be thermal or mechanical. Are external forces meant to be mechanical forces?
L62: MW heating does not help extract the liquid as such but triggers the thawing.
L67: What do the authors mean with "increase the solutes in the … cryoconcentrate"? Should it be the "concentration of solutes in the liquid phase"?
…
Materials and methods
L99: Could the extractor be described more in detail?
L108: A typical curve of freezing and most preferable, the temperature curve slope would be presented. The freezing rate information is thought to be necessary because of the phase separation in the freezing and shape of ice crystals. Such information is essential for the traceability of the study.
L114: In conclusion, the liquid produced by the partial thawing in the 15 min centrifugation time at 20 °C was a long time in contact with the residual ice when the filter was blocked with an open filter. This would influence diffusion processes between the two phases. The reason for the higher concentration in centrifugal-filter BFC would be the shorter contact time of thawed juice (liquid) with the still frozen juice (solid). For an explanation of the observation, such diffusion processes should be involved in the description.
…
Results and discussion
L220: The values are lower than reported by Santana et al. (2020). The variety was different. What is the importance of the initial concentration for the final concentration? The present study reports with CBFC lower concentrations as Santana et al. (2020). The same freezing and centrifugation technology was used.
L234: Not the filter as such improves the concentration in the liquid, but the reduced contact time of liquid and solid.
L238: check word division: cry-oconcentrated?
L247: Do the authors suppose a correlation of pH and TTA? In this case, a correlation coefficient might support the hypothesis.
L212-250: Self-citation is used extensively in the discussion. Arguments circulate internally.
L248-250: It is hard to understand the sentence. Three times "increase" is used in combination with "causing the opposite phenomena". What do the authors mean with "opposite phenomenon between pH and TTA"?
L257: Do the authors considered that the Lab system's scale goes from a negative to a positive value for a and b when calculating the % of reduction (-50 … 50 for a and b, 0 … 100 for L)? At least for the a-value, this must be checked.
L297: missing dot in abbreviation d.m.
L347-358: The authors discuss deeply the influence of the cultivar on the composition, which is not the original aim of the publication. The same is true for L296-306. What exactly is the importance of this discussion for the qualification of the liquid-solid separation method?
L376: For the same heat transfer rate in all processes, the same amount of liquid would be produced, but a different amount can be removed depending on the separation technique.
L392: For the centrifugal-filtered BFC, 81% appears as concentration, and 20% is residual ice. And the yield of solute is systematically slightly higher than the percentage of concentrate. Considering the increase of TSS or TPC, the concentration factor is 2 or 3 for centrifugal-filter BFC and not as expected 20% maximum. How do the authors explain this difference?
Conclusions
The authors repeat the results but do not present conclusions on the process engineering background. The statement that "the addition of the filter allows a better separation of solution from the ice fraction" is trivial. A comment on the use of the term "better" process is included in the general comments.
Author Response
RESPONSE TO REVIEWER COMMENTS: Reviewer 1
General comments
The manuscript reports about a method to separate the liquid produced during thawing of frozen juice from the (solid) ice fraction by gravitation or centrifugal forces. The phase separation was modified by adding a filter and retaining the solid (ice) fraction on the filter. Thus, the liquid's contact time on the solid phase is different from the three different separation techniques. The solute yield (liquid phase removed) is higher when phase separation is improved by adding a filter to the system. Interestingly, this is also true for the concentration of bioactive compounds or colourants in the solute (liquid phase). The different quantities (separated) and concentrations do not explain via the fraction of thawed material, as the heat transfer rate in the thawing-separation phase is supposed to be the same.
The difference should be related to different diffusion processes (an aspect not considered by the authors). At least the contact time between the liquid and the solid phase is supposed to be different (shorter for centrifuged and by a filter separated phases). In conclusion, the solute migration from high (liquid) to low (residual solid) concentration might be responsible for the observation. It is supposed that such an aspect must be involved in the scientific approach for a journal in chemical engineering. Besides, no information is available about the freezing process (e.g. the freezing rate influences the quality of the phase separation in freezing and freezing point of the residual non-frozen part of the substance). The final statement in the conclusions that "the addition of the filter allows a better separation of solution from the ice fraction" is trivial. "Better" stands for a higher concentration of the solution, but do not consider other aspects as the TRL or maintenance and manufacturing costs with filter centrifuges.
Another issue is the not explained difference between a much higher increase in the values such as TBC and TSS in centrifugal-filter BFC compared to the reference and the concentrate percentage of 80%. The concentration factor in a composition is not merrily explainable with the ratio of concentrate to ice (8:2).
Thank you for the feedback. Now, we will respond to the concerns.
Specific comments
Summary
L16: Please compare initial to final concentration.
Thank you for the suggestion. We have added the initial concentration of the fresh juice in the abstract (please see: Abstract, red letters). An important point, the abstract must contain up to 200 words, and for this reason, the abstract was restructured (red letters).
L 18: The given numbers for TBC, AA and yield art not so easy to combine with the information on the process background (spread on different sentences). In the results section, other abbreviations are used (GBFC, CBFC, centrifugal-filter BFC). Consider a harmonization and using for each of the processes an abbreviation.
Thank you for the suggestion. The abstract was restructured (red letters). An important point, the abstract must contain up to 200 words. Additionally, the improvements of the abstract were combined with comments from the reviewer 2. Moreover, the abbreviations of the freeze crystallization methods were harmonized in all the manuscript (red letters).
L23: there is no indication about the difference in the efficiency of TBC or AA retention between centrifugal filter assisted BFC and the other separation technics. Thus, the conclusion, "this research offers new benefits …" is not traceable at this stage of reading. Only the influence of "time" was explained in summary. Also, consider saying that technology offers this advantage instead of the research as such.
Thank you for the observations. We have added information and comparison between centrifugal-filter assisted BFC and the other separation technics. Therefore, the abstract was restructured (red letters), since the abstract must contain up to 200 words. Additionally, we have added a line with your recommendation (red letters).
L23-26: Consider splitting the sentence and improving the readability.
Thank you for the suggestion. The lines were restructured (red letters). An important point, the abstract must contain up to 200 words.
Introduction
L31-37: The generic comments are relatively stand-alone, and the references do not prove a link between them. Avoid creating or overuse such links or specifications with words such as "every day", "thus", or "therefore", "thereby", "however", "hence" etc.
Thank you for the observations. We have changed the lines, and in addition, we have removed the references that cannot be linked with the sense of the lines (please see: 1. Introduction, red letters). Thus, all the references were changed in the manuscript (red letters).
L38: What means "traditional concentration technologies" (= thermal)? And what the authors mean when saying that these technologies "has been evolved" (lower temperature, lower pressure?).
Thank you for the questions. Indeed, we indicate thermal technologies. Therefore, we have added the word "thermal" in the line (please see: 1. Introduction, red letters). We refer to changes in pressure, decrease in concentration temperature, decrease in concentration times, among others. Thus, these characteristics were added to the lines (please see: 1. Introduction, red letters).
L42: Be more specific when reporting about the deterioration of nutritional properties. Sugar is also a nutrient, for example.
Thank you for the suggestion. We have added more information in the line (please see: 1. Introduction, red letters).
L43: Why the authors differentiate between "novel" and "emerging."
Thank you for the observation. We have decided to eliminate the word “novel”, and thus, only the word "emerging" appears in the manuscript (red letters).
L47: "... increase … the extraction efficiency, percentage recovery … of nutritional … characteristics" is not a valid statement. What is the difference between "extraction efficiency" and "percentage of recovery"? Consider rephrasing.
Thank you for the question and observation. Firstly, the reviewer is right, since “the extraction efficiency, percentage recovery” are more focused on freeze crystallization. Thus, the lines were relocated to the lines about freeze crystallization.
On the other hand, the correct word is “efficiency”. So, we have removed the words “extraction efficiency”, since it could be confused by the readers. In the same way, the “efficiency” is focused on solutes, while “percentage of recovery” is focused on weight. Additionally, the lines were rephrased (please see: 1. Introduction, red letters).
L43-45: The term treatment should be used for all technologies in the list or non.
Thank you for the point. Yes, the term treatment can be used for all technologies. Therefore, we have added the word “treatment” in the line (please see: 1. Introduction, red letters).
L49-50: "Non-thermal" and "low temperature" seem to be expressions that say the same.
Thank you for the observation. Specifically, freeze crystallization is a thermal treatment involving the use of low (below 0°C) temperatures. Therefore, the lines were rephrased (please see: 1. Introduction, red letters).
L51: Total freezing of water in a solution is not possible. Total freezing of water and subsequent separation of unfrozen is not precise and would not be the right description of the process.
Thank you for the point. Indeed, the total freezing of water in a solution is not possible. The expression is used to demarcate the types of freeze crystallization available. However, we have decided rephrased this expression to avoid confusion for the reader (please see: 1. Introduction, red letters).
L54: Complete freezing of the liquid solution is impossible. Also, it should be partial thawing of the frozen solution before separation from the still frozen part.
Thank you for the point. In this case, the expression refers to the fact that the entire solution is subjected to freezing step. Thus, we have decided to change the line to avoid confusion for the reader (please see: 1. Introduction, red letters).
L59: What the authors mean precisely with "natural thawing"?
Thank you for the question. The meaning of "natural thawing" refers to the thawing without the use of any external force that influences the extraction of the cryoconcentrated fraction from the ice fraction. In “natural thawing”, the room temperature affects the separation process.
L61: The authors merge thermal (MW) and mechanical (centrifugation) processes and classify both processes where external forces are applied. Please clarify and be specific with the use of terms. Driving forces of a process might be thermal or mechanical. Are external forces meant to be mechanical forces?
Thank you for the question. Specifically, an external force in freeze crystallization is an assisted technique that accelerates the thawing step or improves the separation step. For this reason, we have mentioned microwave heating, centrifugation, and vacuum, as the extra force in the freeze crystallization process, unspecified in the use of temperature or mechanical force. However, the reviewer is right, and for this reason, we have changed the lines to clarify the point about the assisted techniques in freeze crystallization (please see: 1. Introduction, red letters).
L62: MW heating does not help extract the liquid as such but triggers the thawing.
Thank you for the observation. This point is connected with the previous one. Thus, we have rewritten the lines to clarify the meaning of the assisted techniques (please see: 1. Introduction, red letters).
L67: What do the authors mean with "increase the solutes in the … cryoconcentrate"? Should it be the "concentration of solutes in the liquid phase"?
Thank you for the question. Indeed, we mean the liquid phase. In this way, we have changed the line to be more specific in the sense of it (please see: 1. Introduction, red letters).
Materials and methods
L99: Could the extractor be described more in detail?
Thank you for the question. We have added more details on the extractor (please see: 2. Materials and Methods, 2.2. Raw material and juice preparation, red letters).
L108: A typical curve of freezing and most preferable, the temperature curve slope would be presented. The freezing rate information is thought to be necessary because of the phase separation in the freezing and shape of ice crystals. Such information is essential for the traceability of the study.
Thank you for the suggestion. Indeed, a typical curve of freezing and he temperature curve slope would be excellent values to confirm the results obtained. In this regard, we have previously determined results from the typical curve of freezing. Therefore, it is a methodology that we dominate in our laboratory. However, in this opportunity, we will not be able to obtain more results due to the COVID-19 pandemic.
Specifically, in 2020, Chillán (Chile) was negatively impacted by the COVID-19 pandemic, and from March to October, we were in total quarantine due to the infections COVID-19. In October 2020, the number of infections per day was constant, and thus, the Universities allowed postgraduate students to enter laboratories to obtain results for their theses. However, in December, the numbers of infections per day increased significantly, and thus, in January 2021, the authorities sent Chillán to total quarantine. Hence, actually, we are still in total quarantine, therefore, we cannot go to the University to work, and thus, it is not possible to perform a typical curve of freezing and other determinations due to the multiple restrictions derived from the COVID-19 pandemic.
Additionally, we added the curve for COVID-19 infections in Chile, and an electronic note (in Spanish) with the start of the total quarantine in Chillán in January 2021.
http://www.ladiscusion.cl/chillan-y-chillan-viejo-retroceden-a-cuarentena-total-este-sabado/
Today, another note (in Spanish) has appeared, and this mentions that authorities will extend the total quarantine in Chillán.
http://www.ladiscusion.cl/probable-extension-de-cuarentena-total-enciende-las-alarmas-en-comunas/
L114: In conclusion, the liquid produced by the partial thawing in the 15 min centrifugation time at 20 °C was a long time in contact with the residual ice when the filter was blocked with an open filter. This would influence diffusion processes between the two phases. The reason for the higher concentration in centrifugal-filter BFC would be the shorter contact time of thawed juice (liquid) with the still frozen juice (solid). For an explanation of the observation, such diffusion processes should be involved in the description.
Thank you for the suggestion. Indeed, the reviewer is right about the filter blocked. Unfortunately, as previously explained, we are not in a position to take more measurements in the laboratories due to the COVID-19 pandemic. Of course, the diffusion processes will be included in future studies on centrifugal-filter freeze crystallization.
Results and discussion
L220: The values are lower than reported by Santana et al. (2020). The variety was different. What is the importance of the initial concentration for the final concentration? The present study reports with CBFC lower concentrations as Santana et al. (2020). The same freezing and centrifugation technology was used.
Thank you for the question. We have carried out a detailed review on the line and manuscript, and we have realized that the reference Santana et al. (2020) is not in the manuscript. Additionally, we did not make any comparison of concentrations with the results obtained by Santana et al. (2020).
L234: Not the filter as such improves the concentration in the liquid, but the reduced contact time of liquid and solid.
Thank you for the observation. The reviewer is right. However, we believe that the filter could still concentrate the liquid in the separation process. We believe that it would be very interesting to study the filter, i.e., remove the filter from the tube and try to extract the liquid, and thus, analyse the components. Based on this, our next ideas focus on the sample (more quantity) to obtain clarity about the separation process.
L238: check word division: cry-oconcentrated?
Thank you for the observation. This aspect is more related to the format of the manuscript, since this word division is automatic. If the reviewer looks the manuscript, the reviewer will notice that the word division does not appear due to the changes.
L247: Do the authors suppose a correlation of pH and TTA? In this case, a correlation coefficient might support the hypothesis.
Thank you for the question. We have added some lines on a correlation of pH and TTA (please see: 3. Results and Discussion, 3.1. Determination of physicochemical properties, red letters).
L212-250: Self-citation is used extensively in the discussion. Arguments circulate internally.
Thank you for the observation. In this case, we always compare our previous results with the new results, and thus, we can demarcate the differences found, and it allows obtaining a good discussion. In the case of centrifugal-filter BFC, we only have one study for reference, which was done by our research group, and this is the reason for the self-citation. We have found some studies on the possibility of hybrid technologies (the combination of membranes with freeze crystallization), but this study (it is a review) is directed towards desalination. Therefore, to date, we have had to make a self-citation, since the current study is a continuation of the previous study.
L248-250: It is hard to understand the sentence. Three times "increase" is used in combination with "causing the opposite phenomena". What do the authors mean with "opposite phenomenon between pH and TTA"?
Thank you for the observation and question. We have rewritten the lines to give clarity to the reader (please see: 3. Results and Discussion, 3.1. Determination of physicochemical properties, red letters). Specifically, "opposite phenomenon between pH and TTA" refers to the increase of one parameter and decrease of the other parameter.
L257: Do the authors considered that the Lab system's scale goes from a negative to a positive value for a and b when calculating the % of reduction (-50 … 50 for a and b, 0 … 100 for L)? At least for the a-value, this must be checked.
Thank you for the observation and question. We have checked the data, and they are correct. The reviewer is right, the Lab system's scale goes from a negative to a positive value (-100 to 100 for a* and b*, 0 to 100 for L*), but in our case, the results are correct.
L297: missing dot in abbreviation d.m.
Thank you for the observation. We have added the dot (please see: 3.2. Determination of total phenolic content (TPC), total anthocyanin content (TAC), and total flavonoid content (TFC), red letters).
L347-358: The authors discuss deeply the influence of the cultivar on the composition, which is not the original aim of the publication. The same is true for L296-306. What exactly is the importance of this discussion for the qualification of the liquid-solid separation method?
Thank you for the observation and question. The reviewer is right; the influence of the cultivar on the composition is not the original aim of the publication. However, we have discussed on the initial composition of the juice with other studies, since each component can affect the counter-diffusion process of the cryoconcentrate/ice in different ways. Some studies have indicated that the differences in the final concentration, retention of bioactive compounds and antioxidant activity can occur due to the reaction of each molecule through freeze crystallization procedure, i.e., there are changes in polarity or molecular size by the freezing stage and/or centrifugation step, producing a possible selective separation of the components. Additionally, other studies have mentioned that the initial concentration of solutes is a key factor in freeze crystallization, since a higher initial concentration allows greater occlusion between the ice crystals than low initial concentrations, hindering the mass transfer, and in addition, provoking a reduced diffusion in the separation process. For this reason, we make an observation on how external factors change the original composition of the juice, and in turn, the composition can affect the freeze crystallization.
L376: For the same heat transfer rate in all processes, the same amount of liquid would be produced, but a different amount can be removed depending on the separation technique.
Thank you for the observation. Indeed, the reviewer is right. In this case, we use the same conditions in all processes. Therefore, we expect a similar counter diffusion process (cryoconcentrate/ice). However, as previously mentioned, the external force makes the difference in the separation process. Although, it would be very interesting to use different freezing conditions in the freeze crystallization process. There are studies that analyze the effect of different freezing temperatures (0 °C to -20 °C), but there is no focus on heat transfer rate; therefore, it would be very interesting to study this aspect in the future.
L392: For the centrifugal-filtered BFC, 81% appears as concentration, and 20% is residual ice. And the yield of solute is systematically slightly higher than the percentage of concentrate. Considering the increase of TSS or TPC, the concentration factor is 2 or 3 for centrifugal-filter BFC and not as expected 20% maximum. How do the authors explain this difference?
Thank you for the question. These differences can be explained from the components of the juice. As mentioned previously, the components (sugars, proteins, pectin, among others) interact differently in the counter diffusion process in the freezing step, and it can be associated with their molecular structures, since a high number of hydrogen bonds can be formed between the molecules with the water, and thus, these structures can be remained in the water molecules (between the ice crystals), which can reduce or increase the amount of final concentrate extracted from the frozen matrix, and it can finally influence the final mass and concentrated obtained post-cycle. In addition, a future study could be focused on the fraction in the filter, since there are three fractions in the centrifugal-filter BFC, ice, cryoconcentrated and the fraction in the filter. In this way, we could perform a mass balance and determine the lost (remaining) quantities in the filter.
An important point, we have a submitted manuscript, in which we note that flavanols have a lower affinity to remain between ice crystals, and tend to be easily extracted from the ice fraction, affecting the process parameters.
Conclusions
The authors repeat the results but do not present conclusions on the process engineering background. The statement that "the addition of the filter allows a better separation of solution from the ice fraction" is trivial. A comment on the use of the term "better" process is included in the general comments.
Thank you for the comments. We have changed the lines in the conclusions (please see: conclusions, red letters)
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Line 14. crystallization (BFC) on physicochemical parameters, total bioactive compounds (TBC).
the term total bioactive compounds used in this work is not appropriate. Although the determination by the Folin method of the content of phenolic compounds is usually considered total phenolic compounds and the term biactive compounds used by the authors includes not only total phenolic compounds, but anthocyanin and flavonols contents, the three together do not constitute the content of total bioactive compounds. It would be better to use the terms total phenolic compounds total anthocyanin content and flavanol content
Line 59.In BFC, the separation step has been carried out by natural thawing (gravitationa.
gravitationa must be changed to gravitational.
Line 68. Specifically, Orellana-Palma et al. [26] added a filter to the centrifugal BFC process
et al must be written in bold type.
Line 111. Results of centrifugal-filter BFC procedure were compared with gravitational BFC (GBFC) and centrifugal BFC (CBFC) procedures under the same centrifugal-filter BFC.
GBFC and BFC procedures must be explained.
Line 119. 2.4. Determination of physicochemical properties The methods used to measure these properties must be explained.
Line 176.ABTS assay was performed according to Re et al. [32].
et al must be written in bold type. All et al expressions included in the manuscript must be written in bold type.
General comment
Has the sensory acceptance of juices been evaluated? This is an important aspect in estimating whether a food processing method is better. A simple ordering test of the 4 product types could be very helpful.
Author Response
RESPONSE TO REVIEWER COMMENTS: Reviewer 2
Line 14. crystallization (BFC) on physicochemical parameters, total bioactive compounds (TBC).
the term total bioactive compounds used in this work is not appropriate. Although the determination by the Folin method of the content of phenolic compounds is usually considered total phenolic compounds and the term biactive compounds used by the authors includes not only total phenolic compounds, but anthocyanin and flavonols contents, the three together do not constitute the content of total bioactive compounds. It would be better to use the terms total phenolic compounds total anthocyanin content and flavanol content.
Thank you for the suggestions. We have made the changes suggested by the reviewer (please see: Abstract, red letters). Moreover, the abstract was rewritten (red letters), since the abstract must contain up to 200 words, and one keyword was rewritten (red letters). Additionally, the improvements of the abstract were combined with comments from the reviewer 1.
Furthermore, we have made some changes in all the manuscript (red letters), and in the titles of subsections (please see: 2. Materials and Methods, title of 2.5., and 3. Results and Discussion, title of 3.2, red letters).
Line 59. In BFC, the separation step has been carried out by natural thawing (gravitationa. gravitationa must be changed to gravitational.
Thank you for the observation. We have made the change on the indicated line (red letters).
Line 68. Specifically, Orellana-Palma et al. [26] added a filter to the centrifugal BFC process
et al must be written in bold type.
Thank you for the observation. We have reviewed the author's guide to Processes and the guide mentions that "et al." should not be written in bold type. However, once the manuscript is accepted, the editorial office mentions the changes that must be made in the writing format of the manuscript.
Line 111. Results of centrifugal-filter BFC procedure were compared with gravitational BFC (GBFC) and centrifugal BFC (CBFC) procedures under the same centrifugal-filter BFC.
GBFC and BFC procedures must be explained.
Thank you for the suggestion. We have added the gravitational BFC (GBFC) and centrifugal BFC (CBFC) procedures in the manuscript (please see: 2. Materials and Methods, 2.3. BFC procedures, red letters).
Line 119. 2.4. Determination of physicochemical properties. The methods used to measure these properties must be explained.
Thank you for the suggestion. We have added an explication for the methods used in the subsection (please see: 2. Materials and Methods, 2.4. Determination of physicochemical properties, red letters).
Line 176.ABTS assay was performed according to Re et al. [32].
et al must be written in bold type. All et al expressions included in the manuscript must be written in bold type.
Thank you for the observation. We have reviewed the author's guide to Processes and the guide mentions that "et al." should not be written in bold type. However, once the manuscript is accepted, the editorial office mentions the changes that must be made in the writing format of the manuscript.
Author Response File: Author Response.pdf
Reviewer 3 Report
Freeze crystallization is a well-known concentration technology, which is based on the fractional crystallization of water to ice and the subsequent separation of the ice crystals from the concentrated liquid. Removal of this ice at low processing temperatures allows to retain aromatics and flavors - without damaging the thermally fragile components of the liquid food, e.g., juice. Moreover, the product acquires an intense, rich taste. Advantage to this method is that storing concentrates allows to cut down on the volume of storage and transport (while preserving the most useful component of fruit juices - such as vitamins and nutrients). Another advantage to this method is that it can limit bacterial growth - freezing can inhibit infectious organisms and keeps concentrates safe.
A crucible step in the technology is the separation of the ice from the fruit juices. The work shows that this step can be made more effective: The novelty is the use of a centrifugal filter as a second separation step. Preservation of bioactive compounds, antioxidant activity, and color changes were measured and proved to be amended. However, of special interest is the amount of sugar in the solute yield. My question is: Did the authors measure the quantity of sugar entrained in the ice fraction?
My recommendation is to publish the paper, but after some minor revision. Importantly, English needs extensive polishing.
Author Response
RESPONSE TO REVIEWER COMMENTS: Reviewer 3
Freeze crystallization is a well-known concentration technology, which is based on the fractional crystallization of water to ice and the subsequent separation of the ice crystals from the concentrated liquid. Removal of this ice at low processing temperatures allows to retain aromatics and flavors - without damaging the thermally fragile components of the liquid food, e.g., juice. Moreover, the product acquires an intense, rich taste. Advantage to this method is that storing concentrates allows to cut down on the volume of storage and transport (while preserving the most useful component of fruit juices - such as vitamins and nutrients). Another advantage to this method is that it can limit bacterial growth - freezing can inhibit infectious organisms and keeps concentrates safe.
A crucible step in the technology is the separation of the ice from the fruit juices. The work shows that this step can be made more effective: The novelty is the use of a centrifugal filter as a second separation step. Preservation of bioactive compounds, antioxidant activity, and color changes were measured and proved to be amended. However, of special interest is the amount of sugar in the solute yield. My question is: Did the authors measure the quantity of sugar entrained in the ice fraction?
Thank you for the comments. Your comments are very important and motivating for us. Yes, we have measured the quantity of sugar entrained in the ice fractions, since these values are necessary to determine the process parameters. Thus, the values were added with a brief discussion in the manuscript (please see: 3. Results and Discussion, 3.1. Determination of physicochemical properties, red letters) and the values were added in the Table 1. Moreover, a reference was added in the manuscript (red letters).
My recommendation is to publish the paper, but after some minor revision. Importantly, English needs extensive polishing.
Thank you for the observation. It is quite curious, since in all manuscripts submitted to a journal, we previously sent it for edition in American Journal Experts. However, we have noticed that this point was not mentioned in the cover letter, but we have made a revision of the English language on the manuscript.
Author Response File: Author Response.pdf
Reviewer 4 Report
The Abstract is concise and contains sufficient information to highlight the content of the article and the Introduction section provides a clear statement of the problem studied in the present manuscript.
The Materials and methods section are well presented and appropriate for the purpose of research.
Results follow the guidelines described in the Author Guidelines and they are well presented and discussed.
References : The bibliographic references are in accordance with the topic of the article and with the results obtained by other researchers in recent years.
Regarding English Proficiency: there are a few minor language corrections to be made. The authors are advised to carefully check the entire manuscript : line 59 – gravitationa – gravitational; line 154 – catequin - catechin.
The Conclusions of the article are relevant and clearly reflect the results of the study.
Author Response
RESPONSE TO REVIEWER COMMENTS: Reviewer 4
The Abstract is concise and contains sufficient information to highlight the content of the article and the Introduction section provides a clear statement of the problem studied in the present manuscript.
The Materials and methods section are well presented and appropriate for the purpose of research.
Results follow the guidelines described in the Author Guidelines and they are well presented and discussed.
References : The bibliographic references are in accordance with the topic of the article and with the results obtained by other researchers in recent years.
Regarding English Proficiency: there are a few minor language corrections to be made. The authors are advised to carefully check the entire manuscript : line 59 – gravitationa – gravitational; line 154 – catequin - catechin.
The Conclusions of the article are relevant and clearly reflect the results of the study.
Thank you for the comments. Your comments are very important and motivating for us. We have made the changes on the indicated lines (Line 59 and Line 154). In addition, we have made a revision of the English language on the manuscript.
Dr. Patricio Orellana-Palma
Department of Biotechnology
Universidad Tecnológica Metropolitana
Tel: +6-2-27877032
E-mail: [email protected]
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript was improved substantially. Some minor issues must be corrected.
L42: Minerals are given as example for nutrients which show a higher degree of deterioration in thermal treatment. This is certainly not the case. In the context the thermosensitive components must be cited.
L60: “natural thawing (gravitational method)” is still used but is not a scientific terminology. Free versus forced separation ?
L 278: “pH y TTA” should be “pH and TTA”
I regret not seeing comments on some critical issues:
An explanation on the comment L392 (old m.) / L 432 (new m.) is missing. Also, a comment on L258 (old m.) / L291 (new m.) was not given. The approach of combined freezing – separation and thawing - diffusion processes was not considered.
Author Response
RESPONSE TO REVIEWER COMMENTS: Reviewer 1
The manuscript was improved substantially. Some minor issues must be corrected.
L42: Minerals are given as example for nutrients which show a higher degree of deterioration in thermal treatment. This is certainly not the case. In the context the thermosensitive components must be cited.
Thank you for the point. The reviewer is right, since the manuscript has been focused on bioactive compounds and antioxidant activity. Therefore, we have rewritten the lines (please see: 1. Introduction, red letters).
L60: “natural thawing (gravitational method)” is still used but is not a scientific terminology. Free versus forced separation?
Thank you for the question. Indeed, we mean free thawing. Therefore, we have changed the words, and thus, we have used "gravitational thawing". These words were used in other studies (please see: 1. Introduction, red letters).
L 278: “pH y TTA” should be “pH and TTA”
Thank you for the observation. We have changed the word (please see: 3. Results and Discussion, 3.1. Determination of physicochemical properties, red letters).
I regret not seeing comments on some critical issues:
An explanation on the comment L392 (old m.) / L 432 (new m.) is missing. Also, a comment on L258 (old m.) / L291 (new m.) was not given. The approach of combined freezing – separation and thawing - diffusion processes was not considered.
Thank you for the observations. We have added lines on the comment L392 (old m.) / L 432 (new m.) (please see: 3. Results and Discussion, 3.1. Determination of physicochemical properties, 3.4. Determination of process parameters, red letters). Additionally, references were added.
In terms of L258 (old m.) / L291 (new m.), we have checked the CIELab values in our results. An impotart point, our results are based on the changes reflected between the cryoconcentrated solution with the fresh juice, and all the values within the positive scale (Table 1). Previously, we have detailed this point in the manuscript.
Now, if we had negative values, we would have taken the values as absolute value or we can take these values as units within a scale. It is important to mention that we did not carry out the reduction percentage based on the CIELAb scale, only between the values of the samples.
Dr. Patricio Orellana-Palma
Department of Biotechnology
Universidad Tecnológica Metropolitana
Tel: +56-2-27877032
E-mail: [email protected]
Author Response File: Author Response.pdf
Reviewer 2 Report
Thank you very much for the corrections. I think that the manuscript is now ready for its publication
Author Response
RESPONSE TO REVIEWER COMMENTS: Reviewer 2
Thank you very much for the corrections. I think that the manuscript is now ready for its publication.
Thank you for the opportunity. We are very happy because the reviewer accepted our manuscript.
Dr. Patricio Orellana-Palma
Department of Biotechnology
Universidad Tecnológica Metropolitana
Tel: +56-2-27877032
E-mail: [email protected]
Author Response File: Author Response.pdf
