**5. Conclusions**

In summary, the results indicated that levels of phospholipids and FAs were decreased in royal jelly secreted by honeybees fed with single bee pollen. However, as honeybees adapted to the single-pollen diet, levels of phospholipids and FAs gradually increased again. The highest levels appeared on days 18 or 24, but were decreased on day 30. Thus, it suggested that the optimum time point for collecting royal jelly from artificial feeding bee pollen is 18~24 days. Moreover, the average contents of PC and 10-HDA were significantly higher in RJ-Am than in RJ-Pa, indicating that continuous feeding of BP-Am was beneficial to increase the contents of PC and 10-HDA in royal jelly than BP-Pa. Additionally, our findings showed that a forced change from the natural mixed bee pollen diet to a singlepollen diet may negatively influence the quality of royal jelly. This study would provide a new perspective on bee pollen diets and scientific guidance for royal jelly production.

**Supplementary Materials:** The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/foods12030625/s1, Table S1: Lipidomic profiles.

**Author Contributions:** Conceptualization, Q.L. and L.W.; Methodology, Q.L.; Software, E.Z.; Validation, X.L. and D.Z.; Formal analysis, E.Z., Q.W. and X.L.; Investigation, E.Z. and Q.W.; Resources, Q.W. and Q.N.; Data cu-ration, X.L. and D.Z.; Writing—original draft, E.Z. and Q.W.; Writing—review and editing, Q.L.; Visualization, E.Z.; Supervision, Q.N., Q.L. and L.W.; Project administration, Q.N. and L.W.; Funding acquisition, Q.N., Q.L. and L.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the National Natural Science Foundation of China (No. 31372386), the Fundamental Research Fund of Chinese Academy of Agricultural Sciences (No. 125161029000160013), and the Agricultural Science and Technology Innovation Program under Grant (CAAS-ASTIP-2021-IAR).

**Institutional Review Board Statement:** The animal study protocol was approved by the Animal Ethics Committee of Institute of Apicultural Research, Chinese Academy of Agricultural Sciences (Beijing, China) (protocol code: CAAS-IAR-ER0045, approval data: April 2021).

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data available on request due to privacy.

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