Effect of modified atmosphere packaging on microbiological, physiological and chemical qualities of stored carrot|
Tilahun Seyoum Workneh, G. Osthoff, M.S. Steyn
Optimum packaging film for carrots should lead to low condensation, but preventing moisture loss, and maintain optimum gas composition during the storage period. In this study, carrots were packaged in polypropylene (PP) and low density polyethylene (LDPE) films and stored at 0C and ambient temperature (15-25C). After 7 days of 0C storage headspace O2, CO2 and N2 concentrations were 11.85%, 13.38%, and 6.69% for PP films and 3.39%, 3.24% and 4.77% for LDPE films. On the other hand, after 7 days of ambient temperature storage O2, CO2 and N2 concentrations were 6.78%, 28.31%, and 16.15% for PP films and 6.41%, 5.19% and 5.28% for LDPE films. The higher the CO2 content of the headspace the more the sucrose content decreased while the glucose and fructose content changed slower. A general decrease of the sugars (sucrose, glucose and fructose) was observed for all samples packaged in PP. The free sugars in carrots were observed to decrease at a slower rate for packaging in LDPE. Based on these results, it was concluded that LDPE film allowed lower respiration rates and is preferred to the PP material. The number of total aerobic microorganisms was higher in packages stored under ambient conditions than in those stored at 0°C temperature. The lowest counts were observed in the least permeable packaging film (PP) up to day 14. The total number of populations of coliform was higher with PP and LDPE films stored under ambient conditions as compared to those stored at O°C. Packaging films with relatively higher permeability to O2 and CO2 are preferred for maintaining normal respiration of carrots without the occurrence of secondary decomposition during storage. Modified atmosphere packaging combined with low temperature storage of carrots (about 1C) reduces both biological and biochemical activities resulting in improved keeping quality.
Modified atmosphere packaging, polypropylene, low density polyethylene