Modified Atmosphere Packaging of Fresh Beansprouts

Freshly harvested beansprouts displayed a respiration rate of about 1 mmol O 2 kg -1 h -1 at 10°C which was strongly dependent on temperature, a 10-fold increase being observed every 16.5°C (z =16.5°C, ie Q 10 = 4.4). This commodity is also characterised by a high initial microbial load (about 10 7 cells g -1 ). During storage at various temperatures from 1 to 20°C, oxygen uptake rates dramatically increased with time and this phenomenon was well correlated with the development of aerobic microorganisms which reached 10 9 cells g -1 after 2 days at 20°C or 9 days at 1°C. Beansprouts were packaged in films, with permeabilities ranging from 950 to 200 000 ml O 2 m -2 day -1 atm -1 , and stored at 8°C. Due to plant and microbial metabolism, oxygen concentrations decreased steadily within all packs until the onset of plant tissue decay. The latter occurred after 5-6 days with the least permeable films but did not occur within when the film permeability was over 100000 ml O 2 m -2 day -1 atm -1 . However, such films favoured brown discolouration, exudation texture and breakdown. The orientated polypropylene film (OPP) induced anoxic condition within 2 days and favoured anaerobic metabolism and necrosis of the sprouts. In all packages there was a rapid development of aerobic microorganisms and lactic acid bacteria that resulted in the accumulation of acetate and lactate and a decrease in pH. Thus, it clearly appeared that tissue decay was enhanced by microbial activity. At 8°C, 0.24 m 2 of film per kg of sprouts provided the optimal atmosphere composition (ie 5% oxygen and 15% carbon dioxide) when a film permeability of 50000 ml O 2 m -2 day -1 atm -1 was used. These conditions allowed a shelf-life of 4-5 days.