**4. Conclusions**

This study demonstrated the proof-of-principle that tamarillo polyphenols could be effectively encapsulated by cubosome nanoparticles with relatively high loading efficiency and preservation of high antioxidant activity. Compared to the unencapsulated extract, cubosomal encapsulation provided a protective effect to the tamarillo polyphenols under simulated gastrointestinal conditions, exhibiting good free polyphenol concentrations at the end of the intestinal phase. A cubosomal system was employed for the delivery of tamarillo polyphenols via yoghurt, and the addition of encapsulated bioactive improved the physicochemical and nutritional properties of yoghurt. The addition of CUBTAM at increasing concentrations successfully increased the concentration of polyphenols, TPC and antioxidant activity of yoghurts, with controlled stability during digestion, suggesting that polyphenols with enhanced bioavailability could be delivered in a dose-controlled manner. This research informs application of cubosome encapsulation to fortification of food products, for example both water-soluble and lipid-soluble vitamins and carotenoids (β-carotene). However, although the components of cubosomes (monoolein and Pluronic F127) are listed as "generally recognised as safe" (GRAS) by the FDA and approved in principle, further investigations should be carried out before sensory testing or consumption by humans as a food.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/antiox11030520/s1, Table S1: Particle size and polydispersity index of CUB and CUBTAM, Table S2: Concentrations (μg/g FW) of individual polyphenols in yoghurts fortified with CUBTAM before in vitro digestion, Table S3: Concentrations (μg/g FW) of individual polyphenols in yoghurts fortified with CUBTAM after each step of in vitro digestion, Figure S1: Size distribution of CUB () and CUBTAM (-), Figure S2: Concentration of polyphenols added into cubosome ((-) and concentration of polyphenols present in the supernatant (-).

**Author Contributions:** Conceptualization, M.J.Y.Y., T.T.D.; Methodology, T.T.D., M.J.Y.Y.; Software, T.T.D.; Validation, T.T.D., M.J.Y.Y.; Formal Analysis, T.T.D.; Investigation, T.T.D.; Resources, M.J.Y.Y., E.R.; Data Curation, T.T.D., M.J.Y.Y.; Writing—Original Draft Preparation, T.T.D.; Writing—Review and Editing, M.J.Y.Y., E.R.; Visualization, T.T.D., M.J.Y.Y.; Supervision, M.J.Y.Y., E.R.; Project Administration, M.J.Y.Y., E.R.; Funding Acquisition, M.J.Y.Y., E.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received a Performance Based Research Fund and internal postgraduate research project funds from the Auckland University of Technology. A PhD scholarship for the first author and internal project fund from Riddet Institute was also received.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data are contained within the article and supplementary material.

**Acknowledgments:** The authors would like to acknowledge the Auckland University of Technology for the Performance Based Research Funding and postgraduate research project funds received for the project. The authors would like to thank the Riddet Institute for the Doctoral Scholarship provided to the first author, and the internal project fund to support the research. We also thank DuPont Nutrition and Bioscience (Danisco Ltd.) for supplying Dimodan®. We thank Azelis New Zealand for supplying Novozym to our research.

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