Carvacrol and eugenol were encapsulated in micellar nonionic surfactant solutions to increase active component concentrations in the aqueous phase and used to treat two strains of Listeria monocytogenes (Scott A and 101) and two strains of Escherichia coli O157:H7 (4388 and 43895) grown as biofilms in a Centers for Disease Control and Prevention reactor. L. monocytogenes biofilms were grown in two different growth media, 1:20 TSB and Modified Welshimer's broth (MWB), while E. coli O157:H7 was grown in M9. In general, L. monocytogenes strains were more resistant to both micelle-encapsulated antimicrobials than E. coli O157:H7 strains. The two antimicrobials were equally effective against both strains of E. coli O157:H7, decreasing viable counts by 3.5 to 4.8 log CFU/cm(2) within 20 min. For both bacteria, most of the bactericidal activity took place in the first 10 min of antimicrobial exposure. Biofilm morphology and viability were assessed by the BacLight RedoxSensor CTC Vitality kit and confocal scanning laser microscopy, revealing an increasing number of dead cells when biofilms were treated with sufficiently high concentrations of carvacrol- or eugenol-loaded micelles. This study demonstrates the effectiveness of the application of surfactant-encapsulated essential oil components on two pathogen biofilm formers such as E. coli O157:H7 and L. monocytogenes grown on stainless steel coupons.
The effect of infant formulas supplemented with functional ingredients on calcium (Ca), magnesium (Mg) and phosphorus (P) bioavailability was investigated in rats. Seven follow-up infant formulas containing probiotics (Bifidobacterium bifidum and Bifidobacterium longum), prebiotics (galactooligosaccharides at 12, 50 and 100 g kg −1 ) or synbiotics (bifidobacteria and galactooligosacccharides) were administered to weanling rats for 30 days. A 3 day mineral balance was performed over three periods (8-10, 18-20 and 28-30 days) to monitor mineral apparent absorption and retention ratios and physiological and nutritional parameters. Feeding rats on infant formula-based diets showed high feed efficiency (≥0.46). It was found that infant formulas supplemented with probiotics and/or prebiotics for 30 days increased Ca, Mg and P bioavailability in rats. Mineral apparent absorption and retention ratios were higher than 90% for Ca and P and 80% for Mg during the first balance period regardless of the infant formula used, but they decreased during the next two balance periods. Although it was not possible to select one infant formula as the best to improve mineral absorption, the 100 g kg −1 prebiotic and 50 and 100 g kg −1 synbiotic infant formulas were the most efficient at increasing Ca, Mg and P bioavailability compared with the control group.
The antimicrobial efficacy of carvacrol and eugenol, two essential oil compounds, encapsulated in a micellar nonionic surfactant solution on four strains of Listeria monocytogenes (Scott A, 101, 108, and 310) and four strains of Escherichia coli O157:H7 (H1730, E0019, F4546, and 932) growing as colony biofilms was investigated. Carvacrol and eugenol were encapsulated in Surfynol 485W at concentrations ranging from 0.3 to 0.9% (wt/wt) at a surfactant concentration of 5% (wt/wt). Colony biofilms were grown on polycarbonate membranes resting on agar plates containing antimicrobial formulations. Cells were enumerated after 0, 3, 6, 9, 24, 48, and 72 h of incubation. Colony biofilms of all E. coli O157:H7 strains were more sensitive to both antimicrobial systems than L. monocytogenes strains. Surface-grown E. coli O157:H7 viable cell numbers decreased below detectable levels after exposure to encapsulated essential oil compounds for > 3 h at all tested concentrations, except for E. coli O157:H7 F4546, which grew slowly in the presence of < 0.5% (wt/wt) eugenol. L. monocytogenes Scott A and 101 were more resistant to eugenol than carvacrol at sublethal concentrations (< 0.5% [wt/wt]). Carvacrol was effective at any concentration against L. monocytogenes 108, whereas concentrations of > 0.5% (wt/wt) eugenol were required for inactivation. L. monocytogenes 310 was equally sensitive to both essential oil compounds. Results suggest that surfactant-encapsulated generally recognized as safe essential oil compounds may offer a new means to control the growth of food pathogens such as E. coli O157:H7 and L. monocytogenes on food contact surfaces.
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