The sanitization of processed vegetable should be carried out in order to obtain a microbiologically safe food. Among sanitizers, chlorine, in its various forms, is the most widely used in food. The use of chlorine as chlorine dioxide is interesting since it does not react with the organic material, avoiding formation of trihalomethanes, which have been identified as carcinogens. Also chlorine dioxide is effective against pathogenic organisms and can minimize browning reactions.The objective of this study was to evaluate the efficacy of sanitization with chlorine dioxide to reduce the enzymatic browning and the microorganisms in minimally processed snap bean. Minimally processed snap bean samples were inoculated by immersion in contaminant solution of E. coli and Salmonella. Afterwards, the product was sanitized with chlorine dioxide (0; 50; 100 and 200 mg/L) for 10 minutes. The pathogens were monitored immediately after sanitization during four days of storage at 10ºC. In other experiment, minimally processed snap bean samples were sanitized with chlorine dioxide (0; 50; 100 and 200 mg/L) for 10 minutes and stored at 10ºC and evaluated periodically during seven days of storage. The surface color, pH, activity of the enzymes phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO), chlorophyll and carotenoids content, and microbiological aspects were evaluated. The sanitization with chlorine dioxide reduced the counting of E. coli and Salmonella. This reduction was proportional to the increase of chlorine dioxide concentration. Reduction in psychrotrophic bacteria was also noticed in snap bean sanitized with 100 and 200 mg/L. Counting of total coliforms decreased with increasing of the sanitizing solution. The thermotolerant coliform counting was low in all treatments, reaching a maximum of 2.4x10-1 NMP/g and Salmonella was not detected in the samples. The browning of the section surface of snap bean was not controlled by chlorine dioxide, being similar in all treatments, as well as activity of the enzymes related to browning (PAL, POD and PPO) and content of pigments (chlorophyll and carotenoids). Chlorine dioxide was not effective in minimizing browning in minimally processed snap bean, but is effective for reducing microorganisms. Sanitizing with chlorine dioxide at a concentration of 200 mg/L during 10 minutes is indicated to ensure a safe product.
Phaseolus vulgaris; sanitization; microbiology.
