Sample Preparation
Propolis (Kim and Chung 2011) was provided by Withealth
Propolis Co. (Kyungnam, Korea) as an ethanol extract from
100% Korean propolis. The product is aqueous and could
be used directly for analysis. Propolis was refrigerated until
use (5C). Ground pork (20% fat) was obtained from the
local supermarket and frozen (−18C) until needed. Prior to
the experiments, the ground pork was thawed at 5C and
then sterilized at 121C for 15 min.