Evaluation of locally made modified atmosphere packaging for Egyptian green beans

Abstract

This research aimed at investigating whether the locally made plastic bags are suitable as modified atmosphere packaging for fresh Egyptian green beans (Bronco) for export. The beans were packed into two kinds of plastic bags; imported micro perforated Poly Oriented Polypropylene (POP) with thickness of 50 mu m (it is used for exporting the Egyptian green beans) and locally made low density polyethylene continuous films (LDPE) with thicknesses of 30, 40 and 50 mu m. Measurements were conducted every third day up to 15 days on packages stored at room temperature and at 7 degrees C and 90% RH. Measurements included weight loss, permeability to O(2) and CO(2) and color. Results indicated that polyethylene bags with thickness of 30 mu m were the best in preserving the weight at room temperature and bags with thickness of 50 mu m were the best at 7 degrees C. The highest percentage of weight loss occurred with the perforated polyethylene film. The permeability to O(2) and CO(2) differed substantially between continuous and perforated films and resulted in considerable differences in gas exchange trend as we observed few changes in O(2) concentration values with perforated polypropylene film up to 6 days while there were considerable differences in O(2) exchange trend with polyethylene 30, 40 and 50 mu m films at room temperature. The highest decrease in O(2) concentration was observed with polyethylene 50 mu m but the pinholes in polypropylene film led to constant O(2) level and a small change during the whole period of storage at 7 degrees C. The increase of CO(2) concentration was neglected with perforated polypropylene film while it was considerable with polyethylene 30, 40 and 50 mu m films at room temperature. The greatest increase of CO(2) concentration was observed with 50 mu m, but at 7 degrees C, the perforated polypropylene film gave tiny increase of CO(2) level and the polyethylene with the three thicknesses gave inconsistent increase in CO(2) levels. The green color of beans became lighter as "L" value increased with all films at room temperature during the whole period whilst at 7 degrees C the "L" value was almost preserved. The initial measurement showed that the color was deep greenish yellow and became strong yellowish green at the end of the period with all samples at room temperature but the color didn't change and kept deep greenish yellow with all samples at 7 degrees C. Thus, modified atmosphere packaging made from polyethylene maintained the overall quality of green beans when compared to perforated polypropylene film