Bioactive properties of a propolis-based dietary supplement and its use in combination with mild heat for apple juice preservation

•Valuable synergistic effects were obtained when combining heat and propolis.•Combined processes inactivated 5 log10 cycles of E. coli O157:H7.•Addition of propolis would allow reducing treatment time and temperature.•Propolis can improve preservation of apple juice by heat.•Addition of propolis would enrich apple juice in bioactive compounds.

This study characterizes the antioxidant and antibacterial properties of a propolis-based dietary supplement (PDS) and investigates its incorporation into apple juice to decrease the intensity of the heat treatment required to inactivate 5 log10 cycles of Escherichia coli O157:H7. As the source of propolis, we used a PDS containing 0.2 mg/μL of propylene glycol-extracted propolis (propolis). The total phenolic content and antioxidant activity (IC50) of the PDS were 82.15 ± 3.53 mg/g and 0.055 ± 0.003 mg/mL, respectively. Regarding antimicrobial activity, propolis (0.2 mg/mL) was very effective under acidic pH against Listeria monocytogenes EGD-e, inactivating more than 5 log10 cell cycles in 1 h, but hardly inactivated or sub-lethally injured E. coli O157:H7 Sakai. However, incorporating propolis (0.2 mg/mL) into acidic buffer decreased the time needed to inactivate 5 log10 cycles of E. coli O157:H7 Sakai at 51 °C by more than 40 times. Moreover, when combined with heat in apple juice, propolis (0.1 mg/mL) reduced the thermal treatment time and temperature needed to inactivate 5 log10 cycles of E. coli by 75% and 3 °C, respectively. The corresponding PDS concentration did not decrease the organoleptic properties of the apple juice, which implies the possibility of obtaining a sensorially appealing, low-pasteurized apple juice with the functional properties provided by propolis.