Heat treatments control extension growth and enhance microbial disinfection of minimally processed green onions

Extension growth of minimally processed (removal of roots and compressed stem) green onions (Allium cepa L. x A. fistulosum L.) was greatly reduced by storage in air at 0 degreesC, while growth of 10-20 min occurred at 5 degreesC over 10 days. Heat treatments of 52.5 and 55 degreesC water for 4 and 2 min, respectively, were especially effective in reducing growth to less than 5 min during 12-14 days at 5 degreesC. 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 degreesC, but did not affect the overall visual quality or shelf life. Treatments with 52.5 degreesC 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 degreesC for initial microbial disinfection.