Coupling of Water Activity and Colour Development of Roast Duck Skin under Forced Convection Drying
Round 1
Reviewer 1 Report
The paper “Coupling of Water Activity and Colour Development of Roast Duck Skin Under Forced-Convection Drying” seeks to evaluate the effects of temperature and time on colour, 3,4-benzo(a)pyrene (BaP) and 11 heterocyclic aromatic amines (HCAs) in roast duck skin during forced hot-air drying at less than 130 °C. The organization and development of the work is fine, very clear and on the point. Few recommendations for the authors are the following:
- Check reference in line 246
- Identify possible barriers and opportunities in developing hot-air drying technology
- Add limitations of the work, if any
Author Response
Dear Reviewers,
Thank you very much for your valuable and constructive suggestions and comments concerning our manuscript entitled “Coupling of Water Activity and Colour Development of Roast Duck Skin Under Forced-Convection Drying”. Those comments are truly valuable and helpful for enhancing the quality of our paper, as well as the important guiding significance to our research. We have studied all comments carefully and have made substantially corrections of our manuscript. With these revisions, we believe that our revised paper is satisfactory to be accepted for publication in Processes. The point-by-point responses to the comments and suggestions are given in details below.
Reviewer 1
The paper “Coupling of Water Activity and Colour Development of Roast Duck Skin Under Forced-Convection Drying” seeks to evaluate the effects of temperature and time on colour, 3,4-benzo(a)pyrene (BaP) and 11 heterocyclic aromatic amines (HCAs) in roast duck skin during forced hot-air drying at less than 130 °C. The organization and development of the work is fine, very clear and on the point. Few recommendations for the authors are the following:
Comment 1. Check reference in line 246.
A: Yes, thanks for the comment.
（1） “both aw”
Changed to
both aw and temperature
（2）“Ref. [21]”
Changed to
Labuza and Saltmarch [23]
Comment 2. Identify possible barriers and opportunities in developing hot-air drying technology
A: Thank you for your valuable suggestion.
It is well known that consumption of grilled or barbecued meat, fried foods, and diets high in cured meats possibly increase the risk of certain human cancers. There is no doubt that application of forced-convection drying, instead of traditional grilling, at mild temperature, can get a delicious product with lower content of harmful substances. Obviously this cooking method provides opportunities for meat research and industry. At the present, however, some of barriers lies in modification of process rameters for meats from different species.
Comment 3. Add limitations of the work, if any
A: Thanks for the constructive advice. We have added the description about the limitations in the conclusion part.
Original: ‘... with lower content of harmful substances.’
Changed to
... with lower content of harmful substances. At the same time, the development of flavor and the formation of volatile aroma components under forced-convection drying need to be examined further in next work.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments:
In this study, the authors investigated the association among water activity, color development, and hazardous chemicals production in roast duck under hot-air drying at mild temperatures. The contents presented in this manuscript is interesting, and a major revision is required before acceptance.
- The INTRODUCTION part, especially the first paragraph, should be reorganized. For example, in the first paragraph, the authors could list more traditional methods that have been used for meat roast. Also, related models that have been developed to predict the physical and chemical changes of meat should be included.
In the second paragraph, the authors could talk about hazardous substances during processing. More information should be included in this paragraph, for example, the regulations from the local government.
- Line 116, there are duplicate “discharged out of” in the manuscript.
- Whether the water activity of duck carcass has been measured?
- The authors only mentioned how they prepared the standard BaP stock solution for BaP measurement. Information regarding how they measured BaP produced in the real sample should be included.
- Information regarding HCA content analysis in the real sample should also be included.
- What does T mean in Figure 1?
- Line 243, “In most cases, studies investigating both aw were not performed.” Is there something missing?
- Line 265, why the regulation of cereal-based foods was mentioned here?
- Through direct comparing the hazardous chemicals in four different samples, the authors claimed that the developed method could effectively decrease HCAs and BaP content. However, from my point of view, this conclusion cannot be drawn without knowing the materials involved in commercial samples.
Author Response
Dear Reviewers,
Thank you very much for your valuable and constructive suggestions and comments concerning our manuscript entitled “Coupling of Water Activity and Colour Development of Roast Duck Skin Under Forced-Convection Drying”. Those comments are truly valuable and helpful for enhancing the quality of our paper, as well as the important guiding significance to our research. We have studied all comments carefully and have made substantially corrections of our manuscript. With these revisions, we believe that our revised paper is satisfactory to be accepted for publication in Processes. The point-by-point responses to the comments and suggestions are given in details below.
Reviewer 2
In this study, the authors investigated the association among water activity, color development, and hazardous chemicals production in roast duck under hot-air drying at mild temperatures. The contents presented in this manuscript is interesting, and a major revision is required before acceptance.
Comment 1. The INTRODUCTION part, especially the first paragraph, should be reorganized. For example, in the first paragraph, the authors could list more traditional methods that have been used for meat roast. Also, related models that have been developed to predict the physical and chemical changes of meat should be included. In the second paragraph, the authors could talk about hazardous substances during processing. More information should be included in this paragraph, for example, the regulations from the local government. Line 116, there are duplicate “discharged out of” in the manuscript.
A: Thanks for Reviewer’s valuable comments. We have made some substantial modification in the revised manuscript, according to your comments.
(1)In the first paragraph,
Original: “…meat during the roasting process. At high temperature (150–300 °C),…”
Changed to
…meat during the roasting process. Feyissa et al. [3] developed the mathematical model of coupled heat and mass transfer during roasting of meat in a convection oven (oven temperature of 175 °C). The model can be used to improve the prediction of temperature and moisture loss, and to support quality control during roasting. At high temperature (150–300 °C),…
(2)In the second paragraph,
Original: “Roasting meat in a forced…”
Changed to
Due to the carcinogenic properties, the maximum permitted level for BaP in smoked meats and smoked meat products is 2.0 mg/kg, the content of BaP in should not exceed 1.0 mg/kg for processed cereal-based foods (EC, 2011). 5 mg/kg for BaP in grilled pork, lamb, duck and chicken was required by Chinese National Criteria (1994). Roasting meat in a forced…
Two references added:
---EC (European Commission). (2011). Commission regulation (EU) No 835/2011, of 19 August 2011, amending regulation (EC) No 1881/2006 as regards maximum levels for polycyclic aromatic hydrocarbons in foodstuffs. Official Journal of the European Union, L215, 4-8.
----Tolerance Limit of Benzo(a)pyrene in Foods, GB7104-1994
(3) Line 116, there are duplicate “discharged out of” in the manuscript.
A: “discharged out of” was deleted.
Comment 2. Whether the water activity of duck carcass has been measured?
A: Thank you for your comment!
It is thought by authors that it is unnecessary to measure water activity of duck carcass muscle in duck carcass because moisture content is about 50%, water activity of carcass muscle is about 0.97~0.98 even when the internal temperature in duck carcass muscle reaches 85 ℃. As a result, this range value of water activity in carcass muscle could not been involved in the development of the skin surface colour. Thus there is no direct relationship between aw of carcass muscle and the development of surface skin colour.
Comment 3. The authors only mentioned how they prepared the standard BaP stock solution for BaP measurement. Information regarding how they measured BaP produced in the real sample should be included.
A: Thanks a lot for your valuable and constructive suggestion! We have revised the relevant description in the revised manuscript.
Original: “…detection (UPLC-DAD/FLD) (NY/T 1666-2008, China). A UPLC unit (Agi…”
Changed to
…detection (UPLC-DAD/FLD) (NY/T 1666-2008, China). Briefly, 5 g of ground duck skin samples were extracted three times with 45 ml cyclohexane in an ultrasound bath for 27 min. The extract was concentrated nearly to 1 ml in a rotavapour at 40 C. Then the concentrate was extracted two times with 10 ml dimethyl sulfoxide for 8 min. The mixture of the resulting extract and 15 ml of 2.0 g/L sodium sulphate solution was extracted three times with 15 ml cyclohexane for 12 min. The eluate was concentrated nearly to dryness under a stream of nitrogen gas and then diluted to 1.0 ml with formaldehyde for use of analysis of 3,4-benzo(a)pyrene. A UPLC unit (Agi…
Comment 4. Information regarding HCA content analysis in the real sample should also be included.
A: Thanks for your suggestion. According to your comment, the revision has been made as below:
Original: “…the method developed by Yao et al. (2013) [10]. The HCA analysis was performed using high performance liquid chromatography (HPLC) coupled with ultra violet detector (UV) and fluorescence detector was used. Separation was…”
Changed to
…the method developed by Yao et al. [10]. Briefly, 2 g of ground duck skin sample was used for the extraction and purification of HCAs. After solid-phase extraction, the samples were analyzed using high-performance liquid chromatography (HPLC) coupled with ultra violet detector (UV) and fluorescence detector was used. The determination and quantification were performed according to the method described by Yao et al. [10]. Separation was…
Comment 5. What does T mean in Figure 1?
A: Thanks a lot.
Original: “…from each group. The drying process involves…”
Changed to
…from each group. The difference between the surface temperature and internal temperature (dT) = Surface temperature - Internal temperature. The drying process involves….
Comment 6. Line 243, “In most cases, studies investigating both aw were not performed.” Is there something missing?
A: We apologize for the mistake. The word “temperature” was missed.
The correct sentence is
In most cases, studies investigating both aw and temperature were not performed.
Comment 7. Line 265, why the regulation of cereal-based foods was mentioned here?
A: Thank the Reviewer for the comment!
From articles published at present, little information about the relationship between the water activity and colour development for cooked meat is available. As a result, the paper on cereal foods was cited.
Comment 8. Through direct comparing the hazardous chemicals in four different samples, the authors claimed that the developed method could effectively decrease HCAs and BaP content. However, from my point of view, this conclusion cannot be drawn without knowing the materials involved in commercial samples.
A: Thank you for the valuable comment!
The BaP level in raw duck sample was generally below the detection limit used (0.04μg/kg). For examlpe, Rascón, A. J. et al. (2019) analyzed a total of 7 raw meat from European markets. BaP was detected in chicken breast, minced beef and veal fillets), but again at low levels (<0.03μg /kg). BaP was not detected in pork loin, chicken thigh and lamb.
Heterocyclic aromatic amines are compounds produced in meat subjected to high temperature cooking. As a result, from the published literatures, few reports on HCAs of raw meat have been found.
We attach great importance to your comment, and we will carry out the relevant work in the future.
Rascón, A. J. et al. (2019). Trace level determination of polycyclic aromatic hydrocarbons in raw and processed meat and fish products from European markets by GC-MS. Food Control, 101,198–208.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Since the authors have addressed all my concerns, I would suggest acceptance.
