Performance Evaluation of Fiber Near-Infrared (NIR) Optic Probes for Quality Control of Curd Hardness in Cheese Produced by Spray-Dried Milk

Round 1

Reviewer 1 Report

1. The introduction is too long, in addition, the article is also long

2. Symbols of physical quantities should be written in italics.

3. The superscripts in Tables need to be defined more clearly

4. Space should be added between numbers and ± symbol

5. If possible, authors should provide a better resolution Fig. 2.

Author Response

1. The introduction is too long, in addition, the article is also long.

Response: thank you for the observation. The manuscript was the length observed due to journal requirements 4000 words a minimum.

2. Symbols of physical quantities should be written in italics.

Response: Symbols of physical quantities were italicized.

3. The superscripts in Tables need to be defined more clearly

Response: Correction was made as suggested.

4. Space should be added between numbers and ± symbol

Response: Correction was made as suggested.

5. If possible, authors should provide a better resolution Fig. 2.

Response: Correction was made as suggested.

Reviewer 2 Report

This study proposes an innovative approach for the dairy industry to monitor milk coagulation in cheese production. Utilizing multifiber probes and specific wavelengths, researchers aimed to predict curd elasticity during milk coagulation, optimizing the process economically. The study employed randomized block designs, varying protein levels and wavelengths, with 880 nm showing superior sensitivity and stability in response.

This topic is interesting and suitable for the Journal. The approach is also interesting.  

Introduction: Pay attention to justify the text. The aim of the work should be clearly stated at the end of the introduction.

Materials and methods: please add technical details and details of the manufacturer of the NIR device and of the fiber probes.

English level is good enough.

Decision: the work needs light improvement, and my suggestion is to invite authors to resubmit it after minor revisions.

I'm not native speaker, in my opinion english level is good enough.

Author Response

This study proposes an innovative approach for the dairy industry to monitor milk coagulation in cheese production. Utilizing multifiber probes and specific wavelengths, researchers aimed to predict curd elasticity during milk coagulation, optimizing the process economically. The study employed randomized block designs, varying protein levels and wavelengths, with 880 nm showing superior sensitivity and stability in response.

This topic is interesting and suitable for the Journal. The approach is also interesting.  

Introduction: Pay attention to justify the text. The aim of the work should be clearly stated at the end of the introduction.

Response: objective of the study was stated in the end of the introduction.

Materials and methods: please add technical details and details of the manufacturer of the NIR device and of the fiber probes.

Response: technical details and details of the manufacturer of the NIR device and of the fiber probe were provided.

English level is good enough.

Decision: the work needs light improvement, and my suggestion is to invite authors to resubmit it after minor revisions.

Reviewer 3 Report

The manuscript describes a method for determining the optimal cutting time in cheese production from light scattering measurements made by a fiber-optic probe.

Although the method is surely interesting the presentation of the subject is unclear. The meaning of several quantities used in the text and the scope of some of the measurements performed are not clearly explained. I think that the paper could benefit from an extensive revision of the text.

Paragraph 2.2

The scope of the two preliminary experimental design is not well explained. What is the response variable of the experiment? In paragraph 3.1 it is called “voltage signal”, while in tables 2 and 3 it is called “scattering ratio”, but a ratio should be dimensionless (if the ratioed quantities are homogeneous) of have a composite unit of measure (es., m/s, W/m^2). If it is a ratio, what quantities are compared? The scope of the experiment should also be clearly stated. Are the authors aiming at maximizing or minimizing the response variable? Or do they want to minimize/maximize the difference between different light conditions? And when there is no halogen lamp, what is the complementary light condition? Please, explain.

The meaning of the second experiment is also unclear. Why to test the cuvette with water and air if the measurement must be performed in milk? Please explain.

Another unclear thing is the following. After selecting 880 nm as optimal wavelength in the first two experiment. It is again tested, in the third experiment, against two other wavelength (870 and 890 nm) different for the previous one (780 and 980 nm). Why?

Paragraph 2.4

The curve shown in figure 2 is also called “light scattering ratio”. What is the relationship between it and the response variable of tables 2 and 3?

In the paragraph the bracketed word (min) is repeated several times [Es. “first maximum of the firs derivative (min)”], but its role is unclear. Is it a typographic error?

Three times are defined in this paragraph: Tmax, t2max, and t2min, but it is not explained how they are used for predicting the elastic modulus G’ or the cutting time. It is true that a reference (number [12]) is given, but it is not sufficient. A reference can give a deeper insight of the method, but the manuscript must be self-explaining. That is, the reader must be able to understand the procedure without looking at a reference that could be not available.

Paragraph 3.1

Please, note that part of the caption of table 2 is aside the table itself instead of being above or below.

Paragraph 3.3

A quantity V0 is mentioned here that is not defined in paragraph 2.4. Is it the probe output at the initial time? Please, explain its meaning.

The captions of tables 5 and 6 are exchanged.

In tables 5 and 6 several set of coagulation parameters are given, but there is not a discussion about their goodness. Have the authors tried to extract G’ (or the cutting time) from these data and evaluate the correctness of such estimate?

Author Response

The manuscript describes a method for determining the optimal cutting time in cheese production from light scattering measurements made by a fiber-optic probe.

Although the method is surely interesting the presentation of the subject is unclear. The meaning of several quantities used in the text and the scope of some of the measurements performed are not clearly explained. I think that the paper could benefit from an extensive revision of the text.

Paragraph 2.2

The scope of the two preliminary experimental design is not well explained. What is the response variable of the experiment? In paragraph 3.1 it is called “voltage signal”, while in tables 2 and 3 it is called “scattering ratio”, but a ratio should be dimensionless (if the ratioed quantities are homogeneous) of have a composite unit of measure (es., m/s, W/m^2). If it is a ratio, what quantities are compared? The scope of the experiment should also be clearly stated. Are the authors aiming at maximizing or minimizing the response variable? Or do they want to minimize/maximize the difference between different light conditions? And when there is no halogen lamp, what is the complementary light condition? Please, explain.

Response: The experimental design paragraph was improved as suggested.

The meaning of the second experiment is also unclear. Why to test the cuvette with water and air if the measurement must be performed in milk? Please explain.

Response: the test in water and air was done to see if you we used air as pumping agent or not for the fiber probe channel.

Another unclear thing is the following. After selecting 880 nm as optimal wavelength in the first two experiment. It is again tested, in the third experiment, against two other wavelength (870 and 890 nm) different for the previous one (780 and 980 nm). Why?

Response: according to other studies performed by Castillo and Arango, (2018). These wavelengths were test in regular milk and it was tested in our study in spray dried milk to detect possible differences or similarities.

Castillo, M., Arango, O. (2018). A method and a system for determining gel firmness values from inline optical measurements. Barcelona, España. Patente N° EP3036527 B1.

Paragraph 2.4

The curve shown in figure 2 is also called “light scattering ratio”. What is the relationship between it and the response variable of tables 2 and 3?

Response: Before proceeding to the light scattering determinations, an experimental design in light transmission configuration was used and established to determine the impact of the cu-vette wall NIR reflectance and NIR transmittance which are the results of tables 2 and 3.

In the paragraph the bracketed word (min) is repeated several times [Es. “first maximum of the firs derivative (min)”], but its role is unclear. Is it a typographic error?

Three times are defined in this paragraph: Tmax, t2max, and t2min, but it is not explained how they are used for predicting the elastic modulus G’ or the cutting time. It is true that a reference (number [12]) is given, but it is not sufficient. A reference can give a deeper insight of the method, but the manuscript must be self-explaining. That is, the reader must be able to understand the procedure without looking at a reference that could be not available.

Response: The terms are technical and are also used in other studies such as Castillo, M., Arango, O. (2018). A method and a system for determining gel firmness values from inline optical measurements. Barcelona, España. Patente N° EP3036527 B1.

Paragraph 3.1

Please, note that part of the caption of table 2 is aside the table itself instead of being above or below.

Response: Caption is fixed.

Paragraph 3.3

A quantity V0 is mentioned here that is not defined in paragraph 2.4. Is it the probe output at the initial time? Please, explain its meaning.

Response: thank you for the observation, V0 was define.

The captions of tables 5 and 6 are exchanged.

Response: Caption is fixed.

In tables 5 and 6 several set of coagulation parameters are given, but there is not a discussion about their goodness. Have the authors tried to extract G’ (or the cutting time) from these data and evaluate the correctness of such estimate?

Response: Discussion was improved

Reviewer 4 Report

This paper described the prediction of the elastic modulus of curd during milk coagulation in cheese production by using multifiber NIR light scattering probe. The work is sound and hold promise for applying to estimate protein levels in milk. I think this paper can be considered for acceptance after a minor revision.

Comments and suggestions:

1) Please check label of Table 2. Adjustion of the coulum is needed.

2) There are some typos that should be checked, such as 3.2 part, "100, 150, 200, 500 y 1000 ms".

3) How about the application effect towards milk from cow, instead of milk powder? Samples should be extended.

Author Response

This paper described the prediction of the elastic modulus of curd during milk coagulation in cheese production by using multifiber NIR light scattering probe. The work is sound and hold promise for applying to estimate protein levels in milk. I think this paper can be considered for acceptance after a minor revision.

Comments and suggestions:

• Please check label of Table 2. Adjustion of the coulum is needed.

Response: Table was improved

• There are some typos that should be checked, such as 3.2 part, "100, 150, 200, 500 y 1000 ms".

Response: Correction was made as suggested.

• How about the application effect towards milk from cow, instead of milk powder? Samples should be extended.

Response: The objective of the study was to test spray dried milk only since cow milk has been test by  Castillo, M., Arango, O. (2018). A method and a system for determining gel firmness values from inline optical measurements. Barcelona, España. Patente N° EP3036527 B1.