Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 21, 1996
Publication Date: N/A
Interpretive Summary: Microorganisms can have a deleterious effect on the shelf life and quality of fresh-cut spinach; however, we lack information on the microorganisms present and ways to control their growth. A study was undertaken to determine if controlled atmosphere (CA) consisting of low oxygen or low oxygen with elevated carbon dioxide would control the growth of microorganisms on fresh-cut spinach. The mesophilic and psychrotrophic aerobic microorganisms, Pseudomonadacea, Enterobacteriaceae, and Micrococcaceae, increased in population during storage in air or CA, but the increase was less with samples held in CA than in air at 5C. At 10C, the population was 10 to 100 times higher than that of 5C, and because the increased growth was so rapid, CA had no effect on the increase. Coliforms and lactic acid bacteria were not detected, and yeasts remained at low levels in all atmospheres. These results can be used by scientists and industry in developing a low oxygen atmosphere system to control the increased growth of microorganisms if the storage temperature can be maintained at 5C.
Technical Abstract: The effect of low oxygen controlled atmosphere (CA) was studied on different microorganisms of fresh-cut spinach leaves. Samples were stored in air and in CA containing 0.8 percent oxygen or 0.8 percent oxygen - 10 percent carbon dioxide at 5 and 10C for 7-9 days. Periodically, microbial population densities of mesophilic and psychrotrophic aerobic microorganisms, Pseudomonadaceae, Enterobacteriaceae, Micrococcaceae, coliforms, lactic acid bacteria and yeasts were determined. At 5C, CA reduced the numbers of all microbial populations, except lactic acid bacteria and yeasts, by 1.0 to 2.0 logs compared to air. At 10C microbial populations increased similarly regardless of atmosphere and numbers were 10 to 100 times higher than those at 5C. Coliforms and lactic acid bacteria were not detected, and yeasts remained at low levels of 1-10 thousand CFU per gram under both atmospheres. Thus, low oxygen atmospheres scould be used to control the growth of microorganisms on fresh-cut spinach for a storage period limited to 7 days but the temperature must be strictly maintained between 0-5C.