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

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 log(10) cycles of Escherichia coli O157:H7. As the source of propolis, we used a PDS containing 0.2 mg/mu L 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 log(10) cell cycles in 1 h, but hardly inactivated or sub-lethally injured E. coli 0157:H7 Sakai. However, incorporating propolis (0.2 mg/mL) into acidic buffer decreased the time needed to inactivate 5 log(10) cycles of E. coli 0157:H7 Sakai at 51 degrees 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 log(10) cycles of E. coli by 75% and 3 degrees 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. (C) 2015 Elsevier B.V. All rights reserved.