Changes in bacterial flora during manufacturing of vegetable salad

Abstract

  This study examined changes in standard plate counts and bacterial flora during the manufacturing process, including preservation, of vegetable salad based on the following guidelines recommended by the “Manual of hygiene control for large scale cooking facilities” : materials, washing in running water and pretreatment, soaking in detergent and rinsing in running water, sodium hypochlorite bactericide and rinsing in running water, cutting bactericidal treated materials and mixtures and refrigerated storage at 10 °C for 24 and 48 hours. We also examined fluctuations in the nonfermenting gram-negative bacilli (NFGNB) that are widely distributed in vegetables. Standard plate counts and bacterial flora in the vegetables did not significantly change as a result of the above seven processes. Many species of NFGNB isolates were distributed in the vegetables. The proportion of Enterobacteriaceae tended to increase in salad refrigerated at 10°C for 48 hours. The most frequently detected isolates were spore-forming bacteria and Burkholderia cepacia. In addition, most of the bacterial species detected more than once during the seven processes were NFGNB. Although the pathogenicity of NFGNB is generally low for humans, such organisms have emerged as important opportunistic, and infectious pathogens that are often difficult to be managed because they are inherently resistant to various antimicrobial agents. Therefore, vegetables should be cooked and immediately consumed by compromised hosts and individuals receiving home health care.