**4. Conclusions**

The addition of black tea infusion as a nutritional ingredient to the acidified milk gel significantly reduced EOS on day 1 at all addition levels. However, such advantage started disappearing for ADG45% after 7 days of storage; after 28 days, only ADG15% showed similar EOS as the negative control gel and other gels samples all had higher EOS. At 30% or higher incorporation rates of BTI, the texture of the stirred gel became relatively softer and more brittle after 28 days of cold storage. Both phase stability results and changing trend of texture can be explained by the micrographs, SEM and CLSM images provided complementary information regarding the structural characteristics of BTI enriched milk gel systems. These micrographs may be used as good references for future research about tea-enriched ADG system (e.g., yogurt), since the microstructure features of such type of gel system have not ye<sup>t</sup> been extensively reported. The inclusion of BTI led to remarkable increases of the antioxidant activity for the ADG samples. Such increased antioxidant activity is attributed to the increased TPC derived from BTI. The antioxidant capacity obtained from BTI was relatively stable during a 4-week cold storage. Overall, we recommend that 15% incorporation rate of BTI in ADG is the optimum. At this rate, after 28 days storage, EOS and gel firmness was not compromised and WHC was even higher in comparison with the negative control gel. Moreover, at the end of shelf life the TPC was increased nearly 50% in ADG15% compared to ADG0%. Both similar and contradictory results were found in literature resources regarding the impact of supplement of tea infusion on the texture of acidified milk gel. Also, detailed mechanisms of interactions between tea infusion components and dairy proteins remain unclear. Therefore, further research is still needed for revealing these mechanisms.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2304-8158/9/6/831/s1, Figure S1: Supplement Biplot of the PCA.

**Author Contributions:** Conceptualization, C.S.B., M.A.B. and H.C.; methodology, H.Z., H.C., X.G. and C.S.B.; software, H.C. and H.Z.; validation, H.C., H.Z. and M.A.B.; formal analysis, H.C., H.Z. and M.A.B.; investigation, H.C. and X.G.; resources, H.Z., M.A.B., W.C. and X.G.; data curation, H.C; writing—original draft preparation, H.C., H.Z. C.S.B. and M.A.B.; writing—review and editing, H.C., H.Z. C.S.B. and M.A.B.; visualization, H.C., H.Z. C.S.B. and M.A.B.; supervision, C.S.B., M.A.B., H.Z. and G.X; project administration, C.S.B.; funding acquisition, C.S.B. All authors have read and agreed to the published version of the manuscript."

**Funding:** This research received no external funding.

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