Improvement of Texture, Nutritional Qualities, and Consumers’ Perceptions of Sorghum-Based Sourdough Bread Made with Pediococcus pentosaceus and Weissella confusa Strains

Round 1

Reviewer 1 Report

In this research, the authors developed the Improvement of texture, nutritional qualities and consumer’s  perception of sorghum-based sourdough bread made with selected starter cultures, which is a very novel concern.

The article is well structured and the results are well interpreted.

My suggestions are listed bellow:

Line 19 Could you explain why you have decided to ignore the control sample?

Line 38 You need here a reference.

Line 132 what kind of oven did you used? An electric one or other type?

Line 135 Please mention the balance name, producer and the origin country!

Line 138 What quantity did you used to measure the baking yield?

Line 146 Please mention the country of the Chroma Meter!

Line 294-298 I don’t think that this chapter is proper for definitions.

Line 336 In this study, the tannin and total phenols show

Author Response

We appreciate your encouraging comments and suggestions to make the manuscript better. Below are the corrections made:

Line 19: The control was not ignored. The sentence has been reframed as “bread without sourdough addition was used as the control sample” to justify this.

Line 38: The references (Navarro et al., 2017; Sharma et al., 2020) have been added.  .

Line 132: An electric was used and it has been indicated.

Line 135: The balance name, producer and the origin country has been mentioned “ TP-6101, Denver Instrument Co., Germany”. This can be seen on Line 137 to 138.

Line 138: the baking yield was determined using a formula as described by Kiskini et al., 2012 as seen in Line 142  

Kiskini, A., Kapsokefalou, M., Yanniotis, S., & Mandala, I. (2012). Effect of Iron Fortification on Physical and Sensory Quality of Gluten-Free Bread. Food and Bioprocess Technology, 5(1), 385–390. doi:10.1007/s11947-011-0651-2

Line 146:  The country of the Chroma Meter has been mentioned as Japan.

Line 294-298: I don’t think that this chapter is proper for definitions.

Response: We indicated the description of these terminologies so that it will assist the reader to understand the relevance in sourdough bread.

Line 336: “shows” has been changed to “show”

Reviewer 2 Report

In my opinion, the manuscript entitled Improvement of texture, nutritional qualities and consumer’s perception of sorghum-based sourdough bread made with selected starter cultures is an interesting one, well organised and the results are compared with the current state if the art and well explained.

I only have some small comments, as follows:

1. line 15, please delete the space before This study
2. line 31, please rephrase the first sentence, mainly the words: ,,are on the increase globally’’.
3. Lines 38, 48, please delete spaces and verified in the whole manuscript.
4. Line 97 – please delete point after effect.
5. Line 147 – please write L*a*b* in italic; please correct in the whole manuscript.
6. Line 179. In my opinion, in order to analyse the shelf-life of a final baked products and to estimate that the product is safe for consumers further use, microbiological determination must be done. For instance, total yeast and mould should be analysed through SR ISO 21527-2/2008 standard. I highly consider that a visual analysis it’s not enough for comparing the samples and concluding which one has better shelf life.

I agree that generally, bakery products manufactured with sourdough increased their shelf life mainly because of lactic and acetic acids production, but considering that in the present study organic acid were not analysed, microbiological analysis in required.

7. Line 312. Please continue the line till the end of the table including crust colour.
8. Line 336, please delete ,,the’’;
9. line 391. Sensory analysis was made by using 9 hedonic test, therefore, the figure should have also the values 8 and 9 to better understand the attributes of the final baked goods, starting from 1 value and not 0. Please correct and remake the Figure.

Comments for author File: Comments.docx

Author Response

Thank you for the valuable comments and suggestions to make the manuscript better. Below are the corrections made: 

1. Line 15: The space before “This study” has been deleted.
2. Line 31, The first sentence has been rephrased to “is on the rise worldwide”.
3. Excess spaces has been deleted in lines 38, 48, and in the whole manuscript.
4. Line 97 –Point after effect has been deleted as can be seen in Line 98.
5. Line 147 –L*a*b* have been italicized in the whole manuscript.
6. Line 179. We are in agreement with the opinion. The organic acids were only analyzed in the sourdoughs produced with the starter cultures which has been published from preliminary works. However, we have deleted the statement of judging the shelf-life by visual observation from the conclusion of the manuscript. 

1. Line 312: The line has been drawn till the end of the table.
2. Line 336, We have deleted ,,the’’;
3. line 391: The sensory figure has been remade to start values from 1-9.

Reviewer 3 Report

• Any abbreviation used in the manuscript must be clarified beforehand, regardless of how often it is used. Care should be taken to ensure that each reader can follow the written manuscript independently.
• The title should clearly emphasize the starter cultures used, since the scientific correspondence of this manuscript is based on them.
• Since the authors state, "In this present study, we produced sorghum sourdoughs using selected LAB and studied the impacts on the texture and bioactive properties of gluten-free breads," it is expected that the results presented in the abstract meet the stated objectives. Thus, the summary does not provide information on the bioactive properties of gluten-free breads.
• The methods used in this paper are appropriate to the aim of the study.
  • During the fermentation process, how is the humidity in the chamber controlled?
  • I think the term "dough" is more appropriate than "batter".
  • The authors do not provide information on the total mass of the prepared dough. There is no information on the mass of the samples before baking, and the information on weight loss makes no sense without this information.
  • There is no information on the total number of samples, the schedule of measurements, and the number of repetitions, so the statistics analysis have no basis.
  • Please also note the information on colour measurement with the colorimeter, the number of measurements and the instrument settings.
  • For what reason did you freeze-dry bread samples before using a scanning electron microscope?
  • Write mathematical formulas using an appropriate tool and standardize them in the manuscript.
  • Include sensory evaluation questionnaires in the appendix of the manuscript.
  • If the authors state that they used "two replicates" for statistical analysis, what does that mean specifically: two measurements from one batch or two measurements per batch? It is not clear from the manuscript how often and in what way the measurement was repeated, which is very important for the reliability of the statistical analysis.
• Results and discussion
  • The resolution of the samples in Figure 1 is very weak increase it.
  • If you indicate, “Results indicate mean values ± SD" under the table, please try to present the results in this way.
  • Table 3 shows the values for the mass of the samples. Is it the bread mass before or after baking?
  • In the section "3.1. Bread Attributes" are presented results on the basis of which analyses? In addition, in the same chapter, the physico-chemical parameters of sourdough breads are presented. I suggest that this chapter be divided into: External appearance of the bread and the Physicochemical parameters of the bread.
  • Figure 3 in the heading is "Rheological Qualities of sourdough breads (SB)" and the graph shows the results of texture measurements. There is a significant difference between rheological and texture properties. Please correct this title.
  • Also, the same figure shows the texture parameters with different units of measurement N, mm, ... This needs to be changed.

Author Response

Thank you for the useful comments and suggestions to make the manuscript better. Below are the corrections made: 

• All abbreviations used in the manuscript has been clarified beforehand.
• The title has clearly shown the starter cultures used.
• Information on the bioactive properties has been added to the summary section.
• The methods used in this paper are appropriate to the aim of the study.
• The proofing chamber has no functional humidity regulator. Water was manually sprayed occasionally. This can be seen in Line 126 to 127.
• “Batter” has been changed to "dough" in the entire manuscript.
• Information was provided in line 125 of the manuscript, 150 g of the dough were prepared for baking.
• Information on the total number of samples and the number of repetitions has been provided in the Materials and Methods where some were done in duplicates and triplicates for each independent experiment.
• Information on colour measurement with the colorimeter; the number of measurements and the instrument settings have been provided. This can be seen in Line 148 to 152
• The bread samples were freeze-dried before using a scanning electron microscope because it is part of the sample preparation procedure for the microscopy as water vaporization will obstruct the electron beam and affect the clarity of the image.          
• The mathematical formulas have been adjusted using the Microsoft mathematical equation tool.
• Sensory evaluation questionnaires will be included as a supplementary document.
• Depending on the analysis, "two replicates" stated specifically means two measurements per batch.
• Results and discussion
• The resolution of the samples in Figure has been adjusted.
• Correction has been made to the description of the tables.
• The mass of the samples presented on Table 3 was for bread samples after baking. Before baking, the term used were “batter” or “dough”. After baking, “bread” was used for the description
• Section "3.1. The Bread Attributes" has been divided into two: “External appearance of the bread samples” and “Physicochemical parameters of the bread samples” as suggested. The “External appearance of the bread samples” is in 3.1 while 3.2 is the “Physicochemical parameters of the bread samples”
• Thank you for this observation. The heading of Figure 2 has been changed from Rheological Qualities of sourdough breads (SB) obtained with different LAB strains and Control bread to "Texture Parameters of sourdough breads (SB) obtained with different LAB strains and Control bread".
• Thank you for this observation. Each of the parameters of Texture Profile Analysis have different standard unit’s peculiar to each. Correct unit for each parameter is presented.

Thank you very much once again for all the valuable comments and suggestions.

Round 2

Reviewer 3 Report

Dear authors, thank you for considering all the comments you made to improve the manuscript. Below I give you additional corrections that need to be made before the manuscript is published.

• Regarding the comment "How is the humidity in the fermentation chamber controlled during the fermentation process?" and your response "The proofing chamber has no functional humidity regulator. Water was manually sprayed occasionally. This can be seen in Line 126-127.", please add the information that the spraying was done manually.
• Regarding the information about the color measurements (lines 148-153), please add information about the calibration performed prior to the measurements. I believe you performed a calibration, so please provide that information.
• In subsection 2.8. Scanning electron microscopy of the bread samples, please add a reference that supports your statement, "The bread samples were freeze-dried before using a scanning electron microscope, because it is part of the sample preparation procedure for the microscopy, as water vaporization will obstruct the electron beam and affect the clarity of the image."
• Regarding the information "Depending on the analysis, "two replicates" stated specifically means two measurements per batch.", please tell me how many independent batches you performed in this study?
• In Section 3. Results and Discussion, and Subsection 3.1. External appearance of the bread samples, it is necessary to include information in the first sentence of the paragraph about the method used to obtain the results. If the results are based on visual inspection of the photographed image of the samples, please indicate this.
• In Table 4, please provide standard deviation values.
• Line 286: "One of the drawbacks of gluten-free breads is the possession of a lighter colour than wheat bread" - this claim only applies to the crust of the bread. Please correct this.
• In the subsection "3.3. Colour and Textural properties", please look at and explain the results of the difference between the color of the bread crumb and the crust.
• Looking at Figure 1 and the results of the color measurement in Table 4, the L*a*b* values seem quite strange to me. According to Figure 1, the color of the bread crumb is darker and more yellow than the bread crust (which appears pale), but the values in the table show the opposite. Please explain this and correct the discussion.
• In the subsection "3.3. Colour and Textural properties", please explain the parameter "Stiffness". Also, please review the unit of measurement of the "Springiness" (it is usually given as a dimensionless quantity).
• Please consider how to better display the results of the bread texture parameters. When looking at the displayed values, it would be desirable to separate texture parameters such as: Hardness1, Hardness2, Gumminess and Stiffness in one graph and the other values in another graph. Also, recalculate the values for "Stiffness" and specify them in N/mm.
• The authors have been advised to correct the English language.

Author Response

Thank you for the useful comments and suggestions to make the manuscript better. Below are the corrections made:

• Regarding the comment "How is the humidity in the fermentation chamber controlled during the fermentation process?" and your response "The proofing chamber has no functional humidity regulator. Water was manually sprayed occasionally. This can be seen in Line 126-127.", please add the information that the spraying was done manually.

Response: This has been added in Line 128-129

• Regarding the information about the color measurements (lines 148-153), please add information about the calibration performed prior to the measurements. I believe you performed a calibration, so please provide that information.

Response: The standardization with a white calibration plate were: L* = 97.22, a* = -0.19, b*= -0.16. This can be seen in Line 153 - 156

• In subsection 2.8. Scanning electron microscopy of the bread samples, please add a reference that supports your statement, "The bread samples were freeze-dried before using a scanning electron microscope, because it is part of the sample preparation procedure for the microscopy, as water vaporization will obstruct the electron beam and affect the clarity of the image."

Response: There is a reference stated there (Radha & Prakash, 2009). It can be seen on Line 172

• Regarding the information "Depending on the analysis, "two replicates" stated specifically means two measurements per batch.", please tell me how many independent batches you performed in this study?

Response: Two independent batches were performed in this study. Some experiments were done in triplicates with two independent batches. This has been stated in Line 196 to 197

• In Section 3. Results and Discussion, and Subsection 3.1. External appearance of the bread samples, it is necessary to include information in the first sentence of the paragraph about the method used to obtain the results. If the results are based on visual inspection of the photographed image of the samples, please indicate this.

Response: The addition has been included in the manuscript as shown in Line 201

• In Table 4, please provide standard deviation values.

Response: Standard deviation values have been provided as shown in Line 329 - 330

• Line 286: "One of the drawbacks of gluten-free breads is the possession of a lighter colour than wheat bread" - this claim only applies to the crust of the bread. Please correct this.

Response: The information has been added to the sentence. This can be seen on Line 291

• In the subsection "3.3. Colour and Textural properties", please look at and explain the results of the difference between the color of the bread crumb and the crust.

Response: It has been explained that especially the crust colours of gluten-free (GF) breads are usually lighter than wheat breads and, the crust of GF breads made from sorghum tend to be lighter than the crumbs because of gelatinization temperature of sorghum, which can be inadequate while baking, leading to unwanted white patches and streaks on the crust (Schober, 2009; Phattanakulkaewmorie et al., 2011). This can be seen in Line 291 - 294

• Looking at Figure 1 and the results of the color measurement in Table 4, the L*a*b* values seem quite strange to me. According to Figure 1, the color of the bread crumb is darker and more yellow than the bread crust (which appears pale), but the values in the table show the opposite. Please explain this and correct the discussion.

Response: It has been explained that especially the crust colours of gluten-free (GF) breads are usually lighter than wheat breads and, the crust of GF breads made from sorghum tend to be lighter than the crumbs because of gelatinization temperature of sorghum, which can be inadequate while baking, leading to unwanted white patches and streaks on the crust (Schober, 2009; Phattanakulkaewmorie et al., 2011).

• In the subsection "3.3. Colour and Textural properties", please explain the parameter "Stiffness". Also, please review the unit of measurement of the "Springiness" (it is usually given as a dimensionless quantity).

Response: Stiffness is related to the force required to produce a specific deformation of the material under test (Komlenić et al., 2010). This can be seen in Line 310 - 311.

Springiness is usually given as a dimensionless parameter, but it can also be expressed in %, g, or mm, depending on the type of instrument and its settings (Phattanakulkaewmorie et al., 2011).

• Please consider how to better display the results of the bread texture parameters. When looking at the displayed values, it would be desirable to separate texture parameters such as: Hardness1, Hardness2, Gumminess and Stiffness in one graph and the other values in another graph. Also, recalculate the values for "Stiffness" and specify them in N/mm.

Response: The figure two has been modified accordingly.

• The authors have been advised to correct the English language.

Response: The English Language has been corrected in the entire manuscript

Thank you very much once again for all the valuable comments and suggestions.