Current Status of Optical Systems for Measuring Lycopene Content in Fruits: Review

Round 1

Reviewer 1 Report

Manuscript is well written and organized. I suggest to accept this  manuscript in present form.

The using an optical systems for measuring Lycopene content in fruits is very interesting topic in the field in modern Food and Agricultural science.

The manuscript is well written and organized.

Results are original and possess a significant scientific merit.

Conclusions are consistent.

The references are appropriate.

Author Response

We would like to thank for your thoughtful comments and efforts towards publish our manuscript. 

with our best regards

Reviewer 2 Report

The subject of this review paper was to describe the different instrumental methodologies (under the term ‘optical systems’) used in current practice to measure lycopene content in food matrices.

GENERAL COMMENTS

The objective of this review paper is really interesting and deals with the different ways to quantify an important compound, lycopene, in a variety of food systems. As a general evaluation, the manuscript is well written and structured, the figures are helpful and comprehensive and the Tables provide useful information. However, there are significant issues regarding the core of the subject, which are the alternative techniques of measuring lycopene in foods; since it is also included within the title, I do not fully agree to the term ‘optical systems’  for all the methodologies described. Although being based on an optical property of the matrix measured (absorbance, transmittance, etc), chromatographic and other techniques based on spectroscopy are not usually considered as ‘optical’ methods. This a basic issue that needs to be better sustained, if authors decide to maintain this terminology. Another important issue is related to the description of each instrumental technique, which (in some cases) is rather inaccurate (for example, regarding HPLC initials and procedure) it seems like authors have not an experimental experience of such methods in food analysis. At some points, the presentation of certain methods lacks scientific soundness and clarity; this part should be carefully reconsidered by an analyst who is experienced in food instrumental analysis.

SPECIFIC COMMENTS

 Line 21: check the initials for HPLC (High Performance or High Precision..). Why HPLC, a traditional chromatographic method is considered as an optical system?

Line 27: incomplete sentence

Line 55,56,..: choose a uniform way to write the word ‘lycopene’ (I would suggest not to use a capital first letter).

Table 1: I suppose you mean 100 g (on wet basis). The term ‘per piece’ is too general, since each portion does not weigh the same. It is better to provide lycopene content on a uniform base, for example per 100 g of raw fruit, so as to be able to compare.

Line 66: the aim of this work is ..

Line 92: Among the benefits provided are:

In figure 2, correct the spelling for ‘osteoporosis’.

Lines 131/132: in the parentheses 243 and 488, in the unit mw/cm2, make ‘2’ to be a superscript.

Lines 141-142: poorly expressed; please, rephrase.

Line 144: check the spelling of the substance after phytofluene, namely s_-carotene…I guess something is wrong. In Figure 4, it is written as ζ-carotene. Check and correct accordingly.

Line 175: correct the word ‘except’

Line 180: in m2, make ‘2’ a superscript.

In Table 2 correct the word ‘exhibition’ in the first row. Check also Table 2 title; is the lycopene content per piece or per kg, as you indicate within the Table?

§3.4: Decide whether you will write the term ‘gamma’ with a small or a capital letter; it is usually written with the Greek letter γ.

Line 199 (and generally within §4.1): check again how you describe HPLC…try to be consistent with the terminology used. Again, I am rather skeptical whether all instruments described in §4 can be defined as ‘optical systems’, just because their measurements are based on optical properties.

Lines 208-209: bad syntax; please, rephrase.

Line 210: the mobile phase is not necessarily made up of multiple solvents; check and correct.

In figure 5: what do you mean by the box ‘standards’? You need to explain the procedure used not only to identify, but also to quantify a particular substance within a sample.

Line 249: in the case of [50], they used..

Line 253: rephrase

Table 3: It is Diode Array Detector (DAD)..

Table 3 is not well structured, is not clear at all and, in some cases, information presented is not absolutely accurate. I would suggest not to include this Table in the revised manuscript.

In §4.1 there is no information about the precision and the reproducibility, the LOD/LOQ of the method, etc, data necessary to judge its efficiency.

Line 269: explain with the appropriate equation C*(chroma value) and the hue angle. In §4.2 it is important to mention published surveys about correlating lycopene content to L,a,b, C* and h measurements.

Line 287: …that of [63], who used tomato..

In terms of Table numbering, check that in line 312 it is supposed to be Table 4. In Table 3 (meant to be number 4) what do you mean Linear Regression? What does this umber show? And what about Cor. Coefficient? Is that R2? If yes, it can assume only positive values.

And the word ‘Licopeno” should be written in English…in what units? Check the whole Table.

Line321: consists of irradiating..

Line 334: do you mean linear spectroscopy?

Line 350: correct the term R2Ext (make the ‘2Ext’ a subscript).

Improve Figure 7 resolution, not clear at all.

Lines 373-392: Is that analysis based on HPLC? All this part describes a chromatographic analysis; why is it include in this section, which is supposed to be dedicated to spectroscopy?

Line 406: in ‘cm-1’ make the appropriate superscript

In figure 10 correct the word ‘spectrograph’

Lines 450-451: check spaces between words

Line 467: what do you mean ‘The error Q2 of the lycopene..?’ Check carefully.

In the last Table and in §4.1 a point that should be highlighted (in my opinion) is the actual optical property measured (absorbance, transmittance, etc) and provide a critical evaluation of the different methodologies applied. Since this comparison is in the core of the manuscript, it needs a much more profound discussion. This is a weakness that should be carefully addressed by authors.

Lines 501-504: The meaning of this sentence is not clear. Please rephrase

Line 504: absorbance is a property, not a phenomenon

§5 is poorly written and fails to provide useful conclusions/comparisons and evaluation of the different techniques. Needs a thorough re-consideration.

Author Response

We would like to thank for your thoughtful comments and efforts towards improving our manuscript. We note the professional and detailed analysis of our document. 

Author Response File: Author Response.docx