Antilisterial activity of pediocin AcH in model food systems in the presence of an emulsifier or encapsulated within liposomes

Abstract

The listericidal activity of pediocin AcH was evaluated in slurries (5, 10, or 25% in dH 2O) of nonfat dry milk, butterfat, beef muscle tissue, or beef tallow. Slurries were inocubated with Listeria monocytogenes (2-strain mixture; 2.5 × 10 6 cfu/ml) and then with pediocin AcH (30,000 arbitrary units (AU) per ml of slurry). Although pediocin activity was reduced in slurries, sufficient pediocin remained to decrease the listeriae population. For all slurries tested, the greatest decrease in counts of Listeria (1.2–1.8 log 10 cfu decrease) and decrease in pediocin activity (12–54% recovery of original activity) occurred within 1.5 min of addition of pediocin to slurries. Thereafter, counts of Listeria did not change appreciably, but pediocin activity continued to decrease in most treatments for up to 60 min. In general, greater activity was recovered from: (i) slurries of lower (5%) compared to higher (25%) concentrations of food; and (ii) dairy- compared to meat-based slurries. Next, pediocin AcH was encapsulated with phosphatidylcholine-based liposomes before addition to slurries (10%), or was used unencapsulated in slurries (10%) containing the emulsifier Tween 80. Greater pediocin activity (29–62% increase; average over all concentrations) was recovered from slurries containing encapsulated compared to free pediocin AcH. Likewise, greater pediocin activity was recovered from slurries containing an emulsifier (4–90% increase; average over all concentrations) compared to otherwise similar slurries without Tween 80. The additional recovery of pediocin activity afforded by liposomes or Tween 80 underscores the potential for direct application of biopreservatives to provide another hurdle for L. monocytogenes in foods.