Optimization of Valorization of Chicken MDCM to Produce Soluble Protein and Collagen Peptides

Round 1

Reviewer 1 Report

This paper describes the use of enzymatic and PHWE treatment of mechanically deboned chicken meat (a by-product of the chicken processing industry) from which soluble proteins and collagen peptides are recovered. The gelability and solubility of the hydrolysis products were investigated, optimized and, using the response surface methodology, optimal parameters were obtained. Its commercial profitability of this process was also evaluated.

 

1. The idea is clear and consistent with the principle of sustainable development.
2. Response surface methodology optimizes the reaction conditions such as reaction temperature and enzymatic digestion time.
3. Profitability is evaluated to provide a reference for possible commercialization.

 

Lines 14-15 show mechanically deboned chicken meat for the first time, and his abbreviation MDM appears in the "keywords", so the abbreviation should be marked after it.

In the first paragraph of introduction, I suggest to provide a concise description (1~2 sentences) on the trends in converting of meat protein into functional ingredient, you may refer to the state of art review articles, such as https://doi.org/10.1016/j.tifs.2020.09.032.

Lines 35-36 are illogical, the use of "as much as" does not make sense, need to reconstruct the sentence.

Lines 139 and 159 are both labeled "2.4.", including the subsequent subheadings, which need to be readjusted.

Line 218, the phrase "length of the hydrolysis" is not clear and should be revised.

Line 269, "superiority" should be changed to "superiority".

Line 302, reframing the sentence.

Line 352, what is "PHW"? I think it needs to be clarified.

Lines 378 through 179, change to "...chiken bones, sustainable residual materials..."

Line 404, the "2.6" in should be corrected according to the previous changes

Line 419, the phrase "food quality enzymes" is unclear.

Lines 427 to 428 need to be reconstructed as sentences.

Line 450, incorrect form of reference citation.

Line 451, incorrect form of reference citation. It is best to recheck the full reference citation format and make corrections

Author Response

 

We are grateful to the Reviewer for identifying several errors and suggestions to  modify text and add new references. The answers are in enclosed file

 

Author Response File: Author Response.docx

Reviewer 2 Report

The topic is not novel, but highly commendable. I have following suggestions:

1) Some other current litarature should be added, e.g. "Valorization of a By-Product from the Production of Mechanically Deboned Chicken Meat for Preparation of Gelatins" by Mokrejš et al., Molecules, published in January 2021, or "Exploring Effects of Protease Choice and Protease Combinations in Enzymatic Protein Hydrolysis of Poultry By-Products" by Lindberg et al., Molecules, published in August 2021.

2) The main drawback is that the proteases used in the study are descripted only as non-commercial food grade blends of enzymes. A more detailed description is definitely needed.

3) Table 1. Experiments 1, 4 and 11 were conducted under the same conditions (Time 2.5 h, L:S 2 and E:S 0.275), yet the protein yields notably differ (e.g. 75 versus 105 g/kg). No other combination of the factors is repeated in the Table. The text mentions 5 replicates in the centre point. Please explain this and rearrange the table in the same manner as Table 2 (where the six repetitions are presented together as N15-N20). 

4) The discussion is difficult to orient in. Chapter 3.1. "MDM protein hydrolysate production" deals with the results of protein yield from MDM and of protein yield from soluble protein fraction (Table 3), however, the discussion is more oriented on protein yield and extraction from bones - insoluble fraction. The authors suggest superiority of their enzymes, but the only numbers presented for comparison are from studies working with chicken bones (the "waste" after separation), not MDM. The results regarding bones are presented in chapter 3.3. as the nitrogen content. 

5) "Mkg" is not a standard SI unit.

Author Response

Reviewer #2

We are grateful to the Reviewer for identifying errors, that may generate confusion on the overall experimental work and results. The more detailed answers are enclosed.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The manuscript has been improved. Just in proof-reading please delete the  now redundant "chicken" word from the combination "chicken MDCM". The units Mkg nad M€ could have been simply converted to (thousands of) tons and million euros, but it is not a problem.