**4. Conclusions**

PBPs purified from two Andean cyanobacteria from northern Chile showed chemical stability at a pH range from 5 to 8, and temperatures between 0 and 50 ◦C. The pigmented proteins from the LLC-10 strain had no toxic e ffects against *C. elegans*. The highest score at the sensory test was obtained by skim milk that was fortified with PE.

Colors are always attractive to children and induce consumption. The skim milk was selected to incorporate blue PC and red PE because of its low-fat content and its contribution to human health with vitamins, minerals and proteins, particularly to the overweight population.

We conclude that PBPs are natural proteins that can be used as colorants in the formulation of functional food products based on skim milk in the replacement of added artificial colorants. In addition, the native cyanobacterial PBPs have an appropriate level of antioxidant activity, and we propose their potential use as an innovative source of pigments in the pharmaceutical, cosmetic and food industries.

Finally, the UHT pasteurization (138 ◦C, 4 s) of Atacama cyanobacterial PBPs induced a minor denaturation of PE and PC; therefore, they can be added before the skim milk pasteurization process. However, milk usually is heated over 50 ◦C, and, in order to avoid the loss of added PBP coloration

while maintaining bacteriological safety, we propose two alternatives for the use of cyanobacterial PBPs at high temperatures in dairy products before pasteurization. One is the application of molecular biology and genetic tools on PBP genes from mesophilic and thermophilic cyanobacteria in order to increase their stability for biotechnological processes and the safety of new functional foods. The second alternative is the use purified freeze-dried PBPs that are enclosed in sachets that can be added as powder to already pasteurized dairy food before their consumption, avoiding protein denaturation and the loss of antioxidant activity.

**Author Contributions:** Conceptualization, A.G.; methodology, A.G., I.N. and S.S.; investigation, A.G., F.S., V.G., R.G., C.V., J.N., C.T., I.N., J.C., S.S.; writing—original draft preparation A.G.; writing, reviewing and editing, A.G., I.N. and B.G.-S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Semillero de Investigación, Universidad de Antofagasta (grant number: SI-5305); CONICYT-Chile (grant number: CeBiB FB-0001); Financiamiento Asistente de Investigación, VRIIP, Universidad de Antofagasta MINEDUC-UA (grant numbers: ANT1855 y ANT1856); Convenio Marco para Universidades Estatales, Ministerio de Educación Chile (grant number: NEXER ANT 1756).

**Acknowledgments:** Special thanks to Milton Urrutia, Universidad de Antofagasta, for his assistance with the statistics used in this work. We thank Catherine Lizama, Microbiology Laboratory, Universidad de Antofagasta her support in the microbiological analyses.

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