*2.13. Differential Scanning Calorimetry (DSC)*

According to the method reported by Butreddy et al., the glass transition temperature (Tg) of lyophilized powder could be analyzed by differential scanning calorimetry [33]. DSC is used to measure stability, shelf life, denaturation, and other irreversible changes during transportation. About 2 mg of lyophilized powder was hermetically sealed in an alumina crucible with the temperature ranges of 30–250 ◦C at a heating rate of 10 ◦C min<sup>−</sup>1. Calibration was performed with indium before performing the analysis.

### *2.14. X-ray Diffraction (XRD)*

The crystal type and crystallinity of lyophilized powder were measured by X-ray diffractometer (Ultima IV, Rigaku, Tokyo, Japan) with Cu-Kα radiation operating (λ = 1.5406 Å) at 45 kV and 40 mA.

### *2.15. Fourier Transform Infrared Spectroscopy (FTIR)*

ATR-FTIR (IRAffinity-1, Shimadzu, Tokyo, Japan) was used to indicate the chemical structure of lyophilized royal jelly powder. The FTIR spectra of the lyophilized powder were recorded within the range of 400–4000 cm−<sup>1</sup> at ambient temperature (20 ◦C) with 32 times scanning.

### *2.16. Statistical Analysis*

A randomized complete block design was applied and all the experiment was replicated three times. The difference between factors and levels were submitted to the analysis of variance (ANOVA). The determine significant differences (*p* < 0.05) among the means used Tukey tests. The analysis was taken by SPSS software version 19. All the data were presented as mean ± standard deviation.

### **3. Results**
