Preharvest soil management affects the native microflora and quality of butter lettuce

PONCE ALEJANDRA G; AGÜERO MARÍA VICTORIA; ROURA SARA INES; MOREIRA MARÍA R

Foz de Iguazú

Congreso; CIGR International Conference of Agricultural Engineering; 2007

The native microflora of lettuce cultivated in mulch and on bare soil and its evolution during storage at optimal condition was evaluated. Internal, middle and external zones of the lettuceheads 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 days 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 internal and middle zones of mulch lettuce presented lower counts of psycrotrophic bacteria, LAB and yeast and molds.