Evaluation of the Minimum Inhibitory Concentration of Polyphenols Combined with Saccharomyces cerevisiae as Antimicrobials for Growth of Listeria monocytogenes

This study used a completely randomized design with a bifactorial arrangement in triplicate to evaluate dif-ferent concentrations of flavonoid extracts from orange (Citrus sinensis), onion (Allium cepa), tamarillo (So-lanum betaceum) and cocoa (Theobroma cacao) peels in combination with the yeast Saccharomyces cerevisiae to inhibit the growth of Listeria monocytogenes in fruit juices. The shells were dehydrated at 50-57 °C for 8 hours and pulverized. The dehydration yields were: orange (32 %), onion (13 %), tamarillo (14 %) and cocoa (34 %). Flavonoids were extracted with Soxhlet using 70% ethanol for 5 hours, concentrating with a rotary evaporator. They were quantified by UV spectrophotometry and the Folin-Ciocalteu method, being the highest in orange (300,75-372,60 mg Q/L) and onion (205,70-534,96 mg Q/L), while tamarillo presented the lowest, with possible errors in the measurement. Soluble solids losses ranged from 2,30 g (cocoa) to 5,27 g (orange). Cocoa and orange extracts showed greater potential as natural preservatives, inhibiting the growth of Listeria monocytogenes in fruit juices, with a minimum inhibitory concentration of 300 µg/mL and 400 µg/mL, re-spectively.