## 4 Conclusions  
This study demonstrates the potential of oil-in-water (O/W) nanoemulsions as effective delivery systems for bioactive compounds, particularly lycopene and phenolic compounds, for functional beverage development. By employing various oils and incorporating ascorbic acid, nanoemulsions were shown to present improved stability and bioaccessibility of the bioactive compounds. The addition of ascorbic acid enhanced droplet distribution and contributed to better colloidal stability, while olive pomace and fish oil produced stable nanoemulsions with favorable droplet sizes (259.3 to 286.6 nm). The stability of lycopene in the nanoemulsions was influenced by storage temperature, with refrigerated samples (4 \({}^{\circ}\)C) maintaining better stability than those stored at higher temperatures, as demonstrated by a lower degradation rate (\(-\)0.0185 d\({}^{-1}\) at 4 \({}^{\circ}\)C vs. \(-\)0.0334 d\({}^{-1}\) at 25 \({}^{\circ}\)C). Although pH had a minimal effect on lycopene degradation, a slightly lower deterioration rate was observed at pH 7. Bioaccessibility determination showed that the olive pomace oil nanoemulsion had the highest lycopene bioaccessibility (53.8 \(\pm\) 2.6%), while the nanoemulsion with fish oil had the lowest (40.1 \(\pm\) 2.1%). Lipid phase did not affect the bioaccessibility of phenolic compounds, with all tested oils achieving bioaccessibility values over 100%. The developed functional beverage, containing the olive pomace oil nanoemulsion, showed decreased lycopene bioaccessibility (6.2 \(\pm\) 1.8%) compared to the pure nanoemulsion (53.8 \(\pm\) 2.6%), possibly due to the presence of fibers in apple juice which may have a hindering effect. Moreover, the study confirmed that beverage storage at 4 \({}^{\circ}\)C preserved lycopene stability and led to a shelf life of approximately 165 days, based on a 50% reduction in lycopene concentration, while no growth of microorganisms responsible for spoilage of the beverage was noted. The findings indicate that nanoemulsion technology is an effective strategy to enhance the shelf-life, physical stability, and bioaccessibility of bioactives in functional beverages. Additionally, the study supports circular economy practices by valorizing food industry by-products, such as olive and tomato pomace, transforming waste into valuable nutritional resources and promoting more sustainable product development. This approach not only adds nutritional and functional value but also aligns with industry goals for sustainability and innovation, making it a practical and environmentally beneficial solution. These results should be further validated through sensory evaluations to ensure commercial appeal and consumer acceptance. Conceptualization, M.K., I.V.T. and A.N. ; methodology, M.K., I.V.T. and A.N. ; validation, M.K., I.V.T. and A.N. ; formal analysis, M.K., I.V.T., E.R. and A.N. ; investigation, M.K., I.V.T. and A.N. ; resources, P.T. and M.C.G. ; data curation, M.K., I.V.T., E.R. and A.N. ; writing--original draft preparation, M.K., I.V.T. and A.N. ; writing--review and editing, M.K., I.V.T. A.N. and M.C.G. ; visualization, M.K., I.V.T. and A.N. ; supervision, P.T. and M.C.G. ; project administration, P.T. ; funding acquisition, P.T. All authors have read and agreed to the published version of the manuscript. **Funding:** \"The authors declare that this study received funding from the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the \"2 nd Call for H.F.R.I. Research Projects to support Faculty Members & Researchers\" (Project BAC2 FOOD--Number: 03591). The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication\". **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.