**4. Conclusions**

The outcomes from the present study demonstrate that CO2 laser microperforation has high potential to be applied as a skin pretreatment for the freeze-drying of blueberries, which o ffers significant improvement on the process e fficiency and final product quality.

The CO2 laser treatment allowed the arrangemen<sup>t</sup> of microholes that minimally a ffect the quality and appearance of the fruit, serving as pathways for the flow of water vapor from the sublimating interface through the weakened mass transfer resistance of the berry skin, alleviating the pressure development under it, eventually avoiding the fruit bust, and enhancing the final product quality with a reduced processing time. This makes this novel technological approach an attractive alternative over traditional techniques.

Further research will be required to study other perforation arrangements and perforation depths in blueberries as well as other berry fruits during freeze-drying. The impact on energy consumption and cost-e ffectiveness should also be evaluated.

**Author Contributions:** S.A., P.M., J.U. and M.P. conceived, designed the study and wrote the manuscript; R.S., C.R., P.V., Contributed significantly to the design of the paper, edited and wrote some portion of the paper; All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by CONICYT through FONDECYT project number 1161675 (Sergio Almonacid), project number 1181270 (Ricardo Simpson).

**Acknowledgments:** We are grateful for the financial support provided by CONICYT through FONDECYT project number 1161675 (Sergio Almonacid), project number 1181270 (Ricardo Simpson), and project number.

**Conflicts of Interest:** The authors declare no conflict of interest.
