title: Dynamics of indigenous microbial populations of butter head lettuce grown in mulch and on bare soil.
abstract: The native microflora of lettuce cultivated in mulch and on bare soil and its evolution during storage at optimal condition were evaluated. Inner, mid, and outer leaves of the lettuce heads were analyzed separately and the evolution of the microbial populations were fitted to Gompertz and logistic models. The cultivation method (bare soil and mulch) introduced differences in the initial counts, evolution, and tolerance to refrigeration temperatures for some of the microbial populations under study. Most microbial populations from mulch lettuce presented a decline or little growth under refrigerated storage. However, populations from bare soil lettuce presented some growth phase during storage. Lactic acid bacteria from bare soil lettuce presented significant growth after 8 d of storage while LAB from mulch grown lettuce did not. Concurrently with the LAB growth, there was a decline in the coliform counts in bare soil grown lettuce. At the end of storage, the inner and mid leaves of mulch lettuce presented lower counts of psychrotrophic bacteria, LAB, and yeast and molds.
authors.affiliation: Grupo de Investigación en Ingeniería en Alimentos, Facultad de Ingeniería, Univ. Nacional de Mar del Plata, Argentina.
authors.forename: A G
authors.initials: AG
authors.lastname: Ponce
authors.forename: M V
authors.initials: MV
authors.lastname: Agüero
authors.forename: S I
authors.initials: SI
authors.lastname: Roura
authors.forename: C E
authors.initials: CE
authors.lastname: Del Valle
authors.forename: M R
authors.initials: MR
authors.lastname: Moreira
mesh_terms: D000383:Agriculture / Q000379:methods*; D001419:Bacteria / Q000254:growth & development* / Q000302:isolation & purification; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D006801:Humans; D018545:Lactuca / Q000254:growth & development / Q000382:microbiology* / Q000592:standards; D016015:Logistic Models; D011157:Population Dynamics; D012988:Soil Microbiology; D013997:Time Factors