1. The title of the work - “Heat induced changes on the aroma and physico-chemical properties of dulce de leche” may need to be reviewed as the report appears to be focused more on ´The capacity of a direct injection mass spectrometer based on proton transfer reaction (PTR-MS) to monitor the transient changes of the volatile organic compounds (VOCs) during dulce de leche”.
   The work does not reflect multiple heat inducement activities which effect are investigated. Authors may need to review the title to reflect the actual work carried out .

2. Appropriate references should be provided to support the following methodologies employed:
   i Dulce de leche preparation
   ii. Headspace volatile analysis by PTR-MS
   iii. Physicochemical analysis
   iv. Rheological characteristic
   v. Texture analysis

3. Information provided as referenced below under Results and Discussion should have been featured as part of the Methodology
   Page 8, Lines 21 – 31
   Pg. 9, Lines 28-30

4. Referencing system to be amended:
   (Moro and Hough 1985) to be (Moro and Hough, 1985)
   (Fox 1981) to be (Fox, 1981)

5. On Page 20, Table 1, the References provided for each of the Volatile compounds are not well aligned against their respective volatile compound

6. On Page 24, Figure 4, and page 25, Figure 5, the Title of the Figures should be very distinct. All the long explanations provided against the Figure should have been provided under Results

All the earlier observations on the manuscripts had been corrected. (however,the word 'it " needs to be inserted in line 33 of page 3 . i.e. because (it) characterizes....