title: Inhibition of Listeria innocua in hummus by a combination of nisin and citric acid.
abstract: The effect of nisin or citric acid or combinations of these two inhibitors on the inactivation of a cocktail of three Listeria innocua strains was investigated in a model brain heart infusion (BHI) broth and hummus (chickpea dip). In BHI broth, citric acid had a limited ability to inhibit L. innocua growth. Nisin initially reduced L. innocua concentrations by about 3 log cycles; however, L. innocua reached concentrations similar to those of the control after 5 days at 22 degrees C. In combination, the effects of 500 IU/ml nisin and 0.2% citric acid were synergistic and resulted in complete elimination of L. innocua in the BHI broth. The inhibition of L. innocua by nisin (500 or 1,000 IU/g), citric acid (0.1, 0.2, or 0.3%), or their combinations also was evaluated in hummus. Citric acid alone did not affect L. innocua growth or the aerobic bacterial plate count. A combination of 1,000 IU/g nisin and 0.3% citric acid was somewhat effective (approximately 1.5-log reduction) in controlling the concentration of L. innocua and the aerobic plate count for up to 6 days. This combination also may be useful, in addition to proper hygienic practices, for minimizing the growth of the pathogen Listeria monocytogenes in hummus.
authors.affiliation: Department of Clinical Nutrition and Dietetics, Faculty of Allied Health Sciences, Hashemite University, Zarqa, Jordan. murad@hu.edu.jo
authors.forename: M
authors.initials: M
authors.lastname: Al-Holy
authors.forename: H
authors.initials: H
authors.lastname: Al-Qadiri
authors.forename: M
authors.initials: M
authors.lastname: Lin
authors.forename: B
authors.initials: B
authors.lastname: Rasco
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D029863:Cicer / Q000382:microbiology*; D019343:Citric Acid / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004357:Drug Synergism; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D008087:Listeria / Q000187:drug effects* / Q000254:growth & development; D009561:Nisin / Q000494:pharmacology*; D013696:Temperature; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D009561:Nisin; D019343:Citric Acid