Modified Atmosphere Packaging of Fresh Beansprouts

Freshly harvested beansprouts displayed a respiration rate of about 1 mmol O2 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 Q10=4·4). This commodity is also characterised by a high initial microbial load (about 107 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 109 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 200000 ml O2 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 O2 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 m2 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 O2 m−2 day−1 atm−1 was used. These conditions allowed a shelf‐life of 4–5 days.