Seasonal Variation of Biochemical Composition and Non-Volatile Taste Active Compounds in Pearl Oyster Pinctada fucata martensii from Two Selective Strains
Round 1
Reviewer 1 Report
The manuscript from Zhang et al gives valuable information on the nutrition aspects of Pearl oysters grown in two different seasons. My concern, however, the authors measured two factors, season and strain, and carried out two-way ANOVA to analyze the effects of those factors on the nutritional contents but I did not see their discussion on how the interaction of these factors affected the nutritional contents. Furthermore, no conclusion can be found in the manuscript.
Author Response
Thank you for the comments. Those comments are all valuable and very helpful for revising and improving our paper. Revised portions are marked in red in the paper. Furthermore, according to the editor’s advice, more international publications have been cited in the manuscript. Our response of the comments is enclosed at the end of this letter. Thank you again for your assistance.
Question 1: The authors measured two factors, season and strain, and carried out two-way ANOVA to analyze the effects of those factors on the nutritional contents, but I did not see their discussion on how the interaction of these factors affected the nutritional contents.
Reply: Thanks. According to reviewer’s advice, the significance levels of Two-way ANOVAs between strain and sampling season for pearl oyster biological characteristics, biochemical compositions and non-volatile taste active compounds are shown as supplied Table (Table S1, values < 0.05 has been marked in red color). However, the interaction P values of most detected biochemical composition and non-volatile taste active compound parameters, such as crude lipid, glycogen, glutamic acid, aspartic acid, EAA, ΣPUFA, Umami FAA, Sweet FAA, nucleotides, organic acids and betaine, were more than 0.05, which meant almost no interaction between season and strain. Therefore, we could not discuss on how the interaction of these factors affected the nutritional contents.
Question 2: No conclusion can be found in the manuscript.
Reply: According to the reviewer’s advice, the conclusion has been added. In detail, “In present study, the contents of crude lipid, glycogen, EAA and TAA, and profiles of PUFA (most contributed by C22:6n3 and C20:5n-3) were significantly higher in two P. f. martensii strains sampled in February compared to the same strains sampled in June. Similarly, the significantly higher contents in umami FAA, sweet FAA, bitter FAA, total FAA, succinic acid and betaine of two P. f. martensii strains sampled in February were also observed, while opposite results were observed in nucleotide contents. When compared the differences between two P. f. martensii strains sampled in February, the PE strain showed higher ratio of soft tissues, glycogen and taurine contents compared to PP strain, while the contents of ash, umami FAA, sweet FAA, bitter FAA, nucleotides and betaine, and Σn-3 profile in PP were obviously higher than those in PE.”
Author Response File: Author Response.docx
Reviewer 2 Report
The manuscript provides an interesting study, including a wide range of analytical determinations. It is well written and justified. However, performances ought to be carried out before a subsequent revision is done.
Abstract
Line 24: … taurine was the highest … This kind of sentences ought to be avoided. It is the taurine content that is supposed to be high, not taurine itself.
Materials and methods
Only oyster from February and June were studied. Why no more times ? Therefore, the authors ought to describe it as February- and June-samples but ought not to refer to a seasonal study. In fact, can February be considered as a spring time ?
Line 105: … 12 oysters in each group … Please clarify. What groups ?
Line 138: How were the FAME obtained ? What method ? No internal standard was employed; this would be a more accurate method for quantification than the one employed by the authors.
Line 158: Provide more details on quantification.
Line 182: The sampling procedure does not mention replicates. Neither in Tables. It is not clear how the 36 oysters were grouped and possible replicates carried out. This is my most important concern with this manuscript. Substantial clarifications ought to be provided by the authors in this sense.
Conclusions
Some concluding remarks ought to be provided.
Author Response
Thank you for the comments. Those comments are all valuable and very helpful for revising and improving our paper. Revised portions are marked in red in the paper. Furthermore, according to the editor’s advice, more international publications have been cited in the manuscript. Our response of the comments is enclosed at the end of this letter. Thank you again for your assistance.
Question 1: Line 24: … taurine was the highest … This kind of sentences ought to be avoided. It is the taurine content that is supposed to be high, not taurine itself.
Reply: Thanks. The mistakes in this manuscript have been revised.
Question 2: Only oyster from February and June were studied. Why no more times ? Therefore, the authors ought to describe it as February- and June-samples but ought not to refer to a seasonal study. In fact, can February be considered as a spring time ?
Reply: As mentioned in this manuscript, the harvest season of edible P. f. martensii is from February to June because of their full developed gonad and higher edible soft tissues. It is calculated that the harvest time only five months, therefore, only two sampling times were set. Furthermore, according to the reviewer’s advice, the spring and summer were replaced by February and June, respectively.
The Beibu Gulf is in a tropical and semi-tropical region. Its seawater temperature in February reached 15.93 ºC in our experiment, therefore, we classified February as spring in last manuscript. As mentioned above, the spring has been replaced by February in the latest manuscript.
Question 3: Line 105: … 12 oysters in each group … Please clarify. What groups ?
Reply: This sentence has been rewritten as follow: “Then the soft tissues of 36 pearl oysters from the same group were randomly divided into three sub-groups. 12 oysters of sub-group were mixed, homogenized and stored at -80 °C for further composition determination.”
Question 4: Line 138: How were the FAME obtained ? What method ? No internal standard was employed; this would be a more accurate method for quantification than the one employed by the authors.
Reply: The method of FAMEs preparation has been added in the manuscript. In detai, “total lipids were extracted from 2 g of homogenised oyster soft tissues with chloroform–methanol (2:1, V/V), then saponified, followed by esterification, and finally extraction of fatty acid methyl esters (FAMEs) in hexane.”
Question 5: Line 158: Provide more details on quantification.
Reply: Thanks. The quantification of 5′-nucleotide has been rewritten as follow, “The identity and quantity of each nucleotide were assessed by comparing the retention times and the peak areas of each nucleotide standard (Sigma-Aldrich, St. Louis, MO, USA).”
Question 6: Line 182: The sampling procedure does not mention replicates. Neither in Tables. It is not clear how the 36 oysters were grouped and possible replicates carried out. This is my most important concern with this manuscript. Substantial clarifications ought to be provided by the authors in this sense.
Reply: As mentioned in Question 3, 36 pearl oysters of each treatment were randomly divided into three sub-groups. 12 oysters of sub-group were mixed, homogenized and stored at -80 °C for the biochemical composition and non-volatile taste active compounds determination. Therefore, all samples were analyzed in triplicate. Accordingly, the same description has been added in each detected parameter. Furthermore, the number of replication was also supplied in each table.
Question 7: Some concluding remarks ought to be provided.
Reply: Thanks. According to the reviewer’s advice, the conclusion has been added. In detail, “In present study, the contents of crude lipid, glycogen, EAA and TAA, and profiles of PUFA (most contributed by C22:6n3 and C20:5n-3) were significantly higher in two P. f. martensii strains sampled in February compared to the same strains sampled in June. Similarly, the significantly higher contents in umami FAA, sweet FAA, bitter FAA, total FAA, succinic acid and betaine of two P. f. martensii strains sampled in February were also observed, while opposite results were observed in nucleotide contents. When compared the differences between two P. f. martensii strains sampled in February, the PE strain showed higher ratio of soft tissues, glycogen and taurine contents compared to PP strain, while the contents of ash, umami FAA, sweet FAA, bitter FAA, nucleotides and betaine, and Σn-3 profile in PP were obviously higher than those in PE.”