Heat Treatments Control Extension Growth and Enhance Microbial Disinfection of Minimally Processed Green Onions

Abstract

Extension growth of minimally processed (removal of roots and compressed stem) green onions (Allium cepa L. × A. fistulosum L.) was greatly reduced by storage in air at 0 °C, while growth of 10-20 mm occurred at 5 °C over 10 days. Heat treatments of 52.5 and 55 -°C water for 4 and 2 min, respectively, were especially effective in reducing growth to less than 5 mm during 12-14 days at 5 °C. Growth was inhibited irrespective of whether the heat treatments were applied before or after cutting. Heat treatments resulted in higher average respiration rates during 12 days at 5 °C, but did not affect the overall visual quality or shelf life. Treatments with 52.5 °C water alone or in combination with different chlorine concentrations (50 to 400 mg·L^-1 NaOCl, pH 7.0) were more effective than use of water or chlorine solutions at 20 °C for initial microbial disinfection.