title: Antifungal effect of kefir fermented milk and shelf life improvement of corn arepas.
abstract: Fungal contamination negatively affects the production of cereal foods such as arepa loaf, an ancient corn bread consumed daily in several countries of Latin-America. Chemical preservatives such as potassium sorbate are applied in order to improve the arepa's shelf life and to reduce the health risks. The use of natural preservatives such as natural fermented products in food commodities is a common demand among the consumers. Kefir is a milk fermented beverage obtained by fermentation of kefir grains. Its antibacterial and probiotic activity has been exhaustively demonstrated. Our objectives were to determine the antifungal effect of kefir fermented milk on Aspergillus flavus AFUNL5 in vitro and to study if the addition of kefir fermented milk to arepas could produce shelf life improvement. We determined the antifungal effect on solid medium of kefir cell-free supernatants (CFS) obtained under different fermentation conditions. Additionally, we compared the antifungal effect of kefir CFS with that obtained with unfermented milk artificially acidified with lactic plus acetic acids (lactic and acetic acids at the same concentration determined in kefir CFS) or with hydrochloric acid. Finally, kefir was added to the corn products either in the loaf recipe (kefir-baked arepas) or sprayed onto the baked-loaf surface (kefir-sprayed arepas). The loaves' resistance to natural and artificial fungal contamination and their organoleptic profiles were studied. The highest fungal inhibition on solid medium was achieved with kefir CFS produced by kefir grains CIDCA AGK1 at 100 g/L, incubated at 30 °C and fermented until pH 3.3. Other CFS obtained from different fermentation conditions achieved less antifungal activity than that mentioned above. However, CFS of milk fermented with kefir grains, until pH 4.5 caused an increase of growth rates. Additionally, CFS produced by kefir grains CIDCA AGK1 at 100 g/L, incubated at 30 °C and fermented until pH 3.3 achieved higher antifungal activity than CFS from artificially acidified milk with organic acids (CFS L + A) at the same concentration of kefir CFS. Besides, CFS from milk acidified with hydrochloric acid (CFS HCl) showed no fungal inhibition. On the other hand, kefir-baked arepas exhibited significant resistance to natural and artificial fungal contamination. Finally, both kefir-baked and kefir-sprayed arepas retained the organoleptic characteristics of the traditional corn product, but with certain tastes imparted by the kefir fermentation. This work constitutes the first study on fungal inhibition by kefir-fermented milk extending to the protection of corn products of mass-consumption and the possible application as a food preservative.
authors.affiliation: Cátedra de Microbiología, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 115, 1900 La Plata, Argentina; CIDCA-CONICET (Centro de Investigación y Desarrollo en Criotecnología de Alimentos), Universidad Nacional de La Plata, Calle 47 y 116, 1900 La Plata, Argentina.
authors.forename: Raúl Ricardo
authors.initials: RR
authors.lastname: Gamba
authors.affiliation: Departamento de Alimentos, Facultad de Química Farmacéutica, Universidad de Antioquia, Calle 67 No 53-108, DIVIPOLA, 05001000 Medellín, Colombia.
authors.forename: Carlos Andrés
authors.initials: CA
authors.lastname: Caro
authors.affiliation: Departamento de Alimentos, Facultad de Química Farmacéutica, Universidad de Antioquia, Calle 67 No 53-108, DIVIPOLA, 05001000 Medellín, Colombia; Grupo de Investigación en Análisis Sensorial, Facultad de Química Farmacéutica, Universidad de Antioquia, Calle 67 No 53-108, DIVIPOLA, 05001000 Medellín, Colombia.
authors.forename: Olga Lucía
authors.initials: OL
authors.lastname: Martínez
authors.affiliation: Cátedra de Microbiología, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 115, 1900 La Plata, Argentina; Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC-PBA), Calle 526 entre 10 y 11, 1900 La Plata, Argentina.
authors.forename: Ana Florencia
authors.initials: AF
authors.lastname: Moretti
authors.affiliation: CIDCA-CONICET (Centro de Investigación y Desarrollo en Criotecnología de Alimentos), Universidad Nacional de La Plata, Calle 47 y 116, 1900 La Plata, Argentina; Catedra de toxicología, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 115, 1900 La Plata, Argentina.
authors.forename: Leda
authors.initials: L
authors.lastname: Giannuzzi
authors.affiliation: Cátedra de Microbiología, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 115, 1900 La Plata, Argentina; CIDCA-CONICET (Centro de Investigación y Desarrollo en Criotecnología de Alimentos), Universidad Nacional de La Plata, Calle 47 y 116, 1900 La Plata, Argentina; Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC-PBA), Calle 526 entre 10 y 11, 1900 La Plata, Argentina.
authors.forename: Graciela Liliana
authors.initials: GL
authors.lastname: De Antoni
authors.affiliation: Cátedra de Microbiología, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 115, 1900 La Plata, Argentina. Electronic address: anleon@biol.unlp.edu.ar.
authors.forename: Angela
authors.initials: A
authors.lastname: León Peláez
mesh_terms: D000818:Animals; D001231:Aspergillus flavus / Q000187:drug effects* / Q000254:growth & development; D001939:Bread / Q000032:analysis / Q000382:microbiology*; D005285:Fermentation; D005519:Food Preservation / Q000379:methods*; D005520:Food Preservatives / Q000494:pharmacology*; D061353:Food Storage; D000070716:Kefir / Q000032:analysis* / Q000382:microbiology; D019344:Lactic Acid / Q000378:metabolism; D008892:Milk / Q000382:microbiology; D003313:Zea mays / Q000382:microbiology*
chemical_list: D005520:Food Preservatives; D019344:Lactic Acid
keywords: Antifungal; Arepa; Aspergillus flavus; Kefir; Organoleptic profile