Comparative evaluation between different concentrations of ozonizated water on sanitizing of fresh-cut lettuce

Abstract

Ozone (O3) is a potent oxidant and sanitizer, utilized in small concentrations and short contact time in order to inactivate bacteria, yeasts and molds, spores, protozoas and viruses. For this reason, its use has been recommended as an alternative treatment in traditional chlorinated compounds to reduce the microbial load. The aim of this article was to evaluate and compare the effectiveness of the ozonizated water in the sanitization of fresh-cut lettuce. The samples were harvested in the rural zone of Campinas, SP, Brazil, transported to the laboratory and the toilet operation was carried out, removing the external and dirty leaves and also the heart. In sequence, a portion to constitute treatment 1 (T1 - without washing) was removed and four other portions of leaves were separated and submitted to the following treatments: T2) washing in water; T3) immersion in ozonizated water at 1.4 mg L-1; T4) immersion in ozonizated water at 1.6 mg L-1; T5) immersion in ozonizated water at 2.0 mg L-1. The ozone concentration was measured by a commercially available kit (CHEMetrics, Vacu-vials, Ozone K-7402, Calverton, Va., U.S.A.). The efficiency of treatments was evaluated by microbial analysis of: mesophilic and psychrotrophic aerobic bacteria, total coliforms, Escherichia Coli, yeasts and molds, besides the presence of Salmonella spp. Physical-chemical analysis of pH and soluble solids was also performed. Sanitization was effective to diminish the total coliforms count, reducing initial contamination of >1.1x10³ MPN g-1 to 2.3x10¹ MPN g-1 (1.4 and 1.6 mg L-1), and without detecting the presence of E.coli and Salmonella spp. To mesophilic aerobic and psychrotrophic microorganisms, the average initial contamination of samples was 1.9x106 CFU g-1 and 2.1x106 CFU g-1, respectively. After the treatment (1.6 mg L-1), they were reduced to 6.3x103 CFU g-1 and to 2.8x103 CFU g-1, respectively. The largest reductions in microbial load were obtained when ozonizated water at 1.6 mg L-1 was used.