EFFICACY OF SODIUM HYPOCHLORITE AND QUATERNARY AMMONIUM COMPOUNDS ON YEASTS ISOLATED FROM APPLE JUICE (pages 104–119)

摘要

In this work, we evaluated the effectiveness of sodium hypochlorite and ancommercial quaternary ammonium compound against four wild yeast strainsnin their different growth forms: planktonic, sessile and forming microcolonies.nThese yeasts had been isolated from apple juice processing plant, and appropriatenenvironmental conditions were employed throughout the work. Fornplanktonic cells, 4 log reduction was obtained using the lowest concentrationnof sodium hypochlorite (200 ppm) on all tested strains. However, quaternarynammonium chloride was effective only on Zygosaccharomyces sp. in all in-usenconcentrations tested, and only the stronger in-use concentration (1:30) wasneffective on Rhodotorula mucilaginosa. Because of the above results, thendisinfection on sessile yeast cells was performed only with sodium hypochloritensolutions. In cells attached in batch conditions, the highest concentrationnof sodium hypochlorite (500 ppm) was necessary to get 4 log reduction. Innorder to obtain a 3 log reduction on Zygosaccharomyces sp. microcoloniesnformed in laminar flow conditions, the combined action of 0.5% w/v NaOHnand 500 ppm sodium hypochlorite was required. We concluded, thus, that cellsnforming microcolonies under laminar flow conditions were less susceptible tondisinfectants than those suspended or attached in batch conditions. Thesenresults also indicated that attachment and colonization of autochthonousnyeasts must be properly identified to evaluate the effectiveness of disinfectantsnused in apple juice processing plants.