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Penicillium expansum Inhibition on Bread by Lemongrass Essential Oil in Vapor Phase

Mani Lopez, Emma, Valle Vargas, Georgina P., Palou, Enrique, Lopez Malo, Aurelio
Journal of food protection 2018 v.81 no.3 pp. 467-471
Cymbopogon citratus, Penicillium expansum, air, antimicrobial properties, breads, chemical composition, citral, essential oils, gas chromatography, leaves, microwave treatment, physical properties, refractive index, sensory evaluation, specific gravity, spectrometers, spores, steam distillation, vapors, water activity
The antimicrobial activity of lemongrass (Cymbopogon citratus) essential oil (EO) in the vapor phase on the growth of Penicillium expansum inoculated on bread was evaluated, followed by a sensory evaluation of the bread's attributes after EO exposure. The lemongrass EO was extracted from dry leaves of lemongrass by microwave-assisted steam distillation. The chemical composition of the lemongrass EO was determined using a gas chromatograph coupled to a mass spectrometer. The refractive index and specific gravity of the EO were also determined. Bread was prepared and baked to reach two water activity levels, 0.86 or 0.94, and then 10 μL of P. expansum spore (10(6) spores per mL) suspension was inoculated on the bread surface. Concentrations of lemongrass EO were tested from 125 to 4,000 μL/Lair, whereas mold radial growth was measured for 21 days. For sensory evaluation, breads were treated with lemongrass EO vapor at 0, 500, or 1,000 μL/L(air) for 48 h and tested by 25 untrained panelists. The EO yield was 1.8%, with similar physical properties to those reported previously. Thirteen compounds were the main components in the EO, with citral being the major compound. P. expansum was inhibited for 21 days at 20°C with 750 μL of EO/L(air), and its inhibition increased with increasing concentrations of EO. Sensory acceptance of bread exposed to vapor concentrations of 500 or 1,000 μL of EO/L(air) or without EO was favorable; similar and no significant differences (P > 0.05) were observed among them.