Coexistence of Phases in Royal Jelly Detected by Photopyroelectric Calorimetry

Abstract

Four samples of commercial royal jelly (RJ), delivered by different distributors, were characterized by photopyroelectric (PPE) calorimetry. The thermal diffusivity was obtained in the back PPE configuration by performing a sample thickness scan of the phase of the PPE signal. In order to determine the thermal effusivity, a frequency scan of the phase of the PPE signal was performed in the front PPE detection configuration. Similar values for all of the static and dynamic thermal parameters were obtained for all of the investigated samples. Additional phase transitions measurements were performed in the front PPE configuration, in the −15 °C to 5 °C temperature range. The results were divided: two samples presented only one first order solid to liquid phase transition, but other two underwent two phase transitions indicating a coexistence of two different phases that were probably free and bonded water. In conclusion, the PPE method, used in a temperature scan arrangement, offers structural information about these samples.

Keywords:

• Royal jelly
• photopyroelectric calorimetry
• thermal parameters
• phase transitions

Additional information

Funding

This work was financially supported by Romanian Ministry of Research and Innovation, through the Core Program (Program Nucleu), Project No. PN 19 35 02 01.