Aspergillus flavus dose-response curves to selected natural and synthetic antimicrobials

LOPEZ MALO, A; ALZAMORA, STELLA MARIS; PALOU, E

INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2002 vol. 73 p. 213 - 218

0168-1605

Theeffects of selected concentrations of antimicrobials from natural (vanillin,thymol, eugenol, carvacrol or citral) or synthetic (potassium sorbate or sodiumbenzoate) origin on Aspergillusflavus lag time inoculated in laboratory media formulated at water activity (aw) 0.99 and pH 4.5 or 3.5, were evaluated. Time todetect a colony with a diameter >0.5 mm was determined. Mold response wasmodeled using the Fermi function. Antimicrobial minimal inhibitoryconcentration (MIC) was defined as the minimal required inhibiting mold growthfor 2 months. Fermi function successfully captured A. flavus dose?response curves to the tested antimicrobials witha highly satisfactory fit. Fermi equation coefficients, Pc and k, were used to compare antimicrobials and assess theeffect of pH. Important differences inPc and k were observed among antimicrobials, being naturalantimicrobials less pH dependent than synthetic antimicrobials. A large Pc valuerepresents a small antimicrobial effect on A. flavus lag time; thus, high concentrations are needed todelay growth. A. flavus exhibitedhigher sensitivity to thymol, eugenol, carvacrol, potassium sorbate (at pH3.5), and sodium benzoate (at pH 3.5) than to vanillin or citral. MICs variedfrom 200 ppm of sodium benzoate at pH 3.5 to 1800 ppm of citral at bothevaluated pHs.