Non-destructive Approach for the Prediction of pH in Frozen Fish Meat Using Fluorescence Fingerprints in Tandem with Chemometrics

Round 1

Reviewer 1 Report

The manuscript describes a non-destructive method of checking quality with a potential application in automation. While it is an interesting attempt worth publication, the methodology described are not very clear raising several questions on appropriateness of methods. They need to be answered and if necessary be reflected in the text.

 L-54-58. Apart from pH, other factors like temperature, colour and concentration of the raw material do effect the spectral  fluorescence, hence how can the present study be justified? 

Whether the effect of vacuum packing on pH was analysed in the present study? Vacuum packing before freezing is not a usual  practice. Why vacuum pack was necessary?

Freezing and thawing can affect pH. Though the study is comparative and similar effect is expected on each lot, what measure was taken to minimise the effect of freezing.
>
L-76- What is the significance of instant sacrifice by neck breaking method in the present study? Justify the same. 
>
L-109- Is there a significance of adjusting the photo multiplier voltage to 400 V while illuminating the fluorescence microscopy?
>
L110-112 It is mentioned in the manuscript,  that after acquisition of fluorescence spectra, samples were repacked and frozen at -60^0 C  until the pH is measured by traditional methods. How long was it kept  under the above said conditions and whether the storage and low  temperature wouldn’t result in textural/ chemical changes and subsequent pH fluctuations? Justify.

L 120: Sentence  appears incomplete
>
L-136 What was the basis of using 0.02 M sodium iodoacetate in the present study? Whether the described molarity and volume was  sufficient to inhibit the glycolysis in the fish muscle?
>
Whether the pH was measured for the fillets after chilling or immediate freezing? There is lack of clarity, as on which  experiments the fillets were used after chilled storage or after frozen storage.
>
L-221 How much precision was maintained while removing the irrelevant data during PLSR validation models?
>
L-256 Is metabolic rate, the only reason for higher R^2 value for spotted mackerel in PLSR model?

 L-319 Whether any non-ATP compounds are generated as flourophores during the post-mortem anaerobic glycolysis.
>

 L-353 Why the Fluorescence pattern of NADH is showing a dissimilar pattern when compared to other nucleotides?

General observation: Material methods need more clarity.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The study tests fluorescence fingerprints for the prediction of pH and quality assessment in frozen fish fillets. After appropriate standardization the method might have great impact for practical application.

 Comments:

 In line 56 it is stated that temperature might affect fluorescence fingerprints: Is there any information on this issue? In the present study it was not standardized. Lines 81-82: -60°C is no common storage temperature for fish and filets. More common might be -20°C to -25°C. Can you give some additional information on this issue?

 Line 79 What means n = 3

 Lines 110-112: Please indicate time period between fluorescence fingerprint analysis and pH measurements

 Lines 106 – 107: Wave length range = 250 - 800 nm and lines 116-117 wave length range = 200 – 600 nm What is the reason for range difference?

Results and discussion

Chapter:  pH changes in frozen horse and spotted mackerel fish meat: is there a threshold pH value for high quality meat?

 Lines 153-153: the splitting mode of fish 3D-FFs spectra in calibration and validation data sets is unclear

 

Author Response

Please see the attachment

Author Response File: Author Response.pdf