**4. Conclusions**

In conclusion, our overall results showed that the established fermentation for industrial whey has the potential to be a low-cost, scalable process to reduce the environmental impact of whey by reducing its organic content, and holds strong potential as an effective disinfecting agent when applied to lettuce, with better or similar results when compared to a 110 ppm chlorine solution. Also importantly, it did not alter the quality parameters of the shredded loose-leaf lettuce, which is highly prone to decay. Color was not substantially affected, and panelists were not able to discriminate from chlorine treatments. Furthermore, lettuce shreds treated with fermented whey showed a slight reinforcement within the cold storage time. Overall, these results not only suggest that fermented whey is indeed as effective as chlorine, but also corroborates that our technology of whey fermentation is effective in maintaining the quality of lettuce throughout storage.

**Author Contributions:** I.S., M.A.S.S.F., and M.I.S.S. conceived and planned the experiments. I.S., P.F., S.M., M.I.S.S., and A.I.G.L. participated in samples preparation and analysis, data analysis, and interpretation of the results. I.S., P.F., M.I.S.S., and A.I.G.L. wrote the manuscript with input from all authors. I.S., R.M.S.B.F., L.P., and M.A.S.S.F. supervised the research work, contributed to the discussion of the data, and revised the manuscript. All authors contributed suggestions and comments for the final version of the manuscript.

**Funding:** This research was funded by Fundação para a Ciência e a Tecnologia (Portugal, UID/AGR/04129/2013 (LEAF)).

**Acknowledgments:** The authors would like to acknowledge Sara Bernardes Silva, Technical Director of Indústria de Laticínios SA, Portugal, for kindly providing the cheese whey used in this work; Rosália Furtado, Maria João Barreira, Anabela Coelho, from the Food Microbiology Laboratory of Instituto Nacional de Saúde Dr. Ricardo Jorge (INSA) for providing some strains used in this work and for technical assistance; Isabel Barroso and Lidia Joaquim from Universidade Lusófona de Humanidades e Tecnologias (ULHT), for technical assistance.

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