Rapid Detection of Tea Polyphenols in Fresh Tea Leaves Based on Fusion of Visible/Short-Wave and Long-Wave near Infrared Spectroscopy and Its Device Development

Round 1

Reviewer 1 Report

Comments for manuscript applsci-2174014

The manuscript entitled “Rapid detection of tea polyphenols in fresh tea leaves based on fusion of visible/short-wave and long-wave near infrared spectroscopy and its device development” is a good paper that will contribute to the current literature. I have a few recommendations before the paper can be accepted for publication in “Applied Sciences”.

- The authors determined the total phenolic content of tea samples using the Folin-Ciocalteu assay. It is well known from the literature that Folin-Ciocalteu assay is not specific to phenolic compounds. Reducing agents can interfere with the analysis and thus overestimate the content of phenolic compounds. I suggest authors to discuss this issue in the manuscript.

- The conclusion can be extended. Please make recommendations for future research. What more needs to be done?

- In addition to the above, I have another minor remark. Line 164: Please convert rpm to g force.

Author Response

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Reviewer 2 Report

p 1, L41: catechins are flavonoids indeed!

p2, L44-45: Folin-Ciocalteu is also a spectrophotometric method!

p 2, L44-48- please, add other common methods (with references), such as liquid chromatography

p 4, L166- it is not digestion, but rather extraction

p4, L167: how did the Authors bring the extract to volume with preheated methanol???

p 4, L174: what do the Authors mean by eliminating "abnormal values"?

p 5, L176: please, add information on calibration

Details regarding ANOVA analysis methodology should be included in the subchapter discussing methods.

The type of fusion (low, medium vagy high level, chpt. 2.5.3) should be indicated

L205-206: why did the Authors use interpolation for calculation of overlapping wavelengthts, why didn't they use the data from the more precise instrument?

L218-240: when describing PLS it should be mentioned which parameter was estimated from the spectra

Fig. 6: What do colors denote?  It would be informative to represent separately data for the 2 tea types. Please, include information referring to number of spectra and the sample size

L218-219: Please, specify exactly the validation details

Author Response

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Reviewer 3 Report

Dear Authors, 

Tha manuscript with title "Rapid detection of tea polyphenols in fresh tea leaves based on fusion of visible/short-wave and long-wave near infrared spectroscopy and its device development" is very interesting and have practical application for food industry. The device constructed and explained in this article have potential for application in tea industry especially for the breeding of good tea varieties and online detection of fresh tea leaves quality. However, I would suggest few points regarding the discussion of the results:

1. What is precision of the results from this method in comparison to standard NIR and chromatographic methods for detection of polyphenols in fresh tea leaves?

2. Which is the number of polyphenolic compounds which can be identified and quantified with this method in comparison to other published chromatographic methods?

3. Fig. 2 (b) it is not enough visible the NIR spectra?

4. Is there overleaping of few polyphenolic compounds on the same wavelength?

I suggest acceptance of the manuscript after major revision.

Author Response

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