MODIFIED ATMOSPHERE PACKAGING OF TOFU: HEADSPACE GAS PROFILES AND MICROFLORA DURING STORAGE

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Modified atmosphere packaging was investigated as a preservation technique for tofu. Tofu was packaged in air (control) and in 30% carbon dioxide (CO2)/70% nitrogen (N2), accomplished through flushing or vacuum compensation, and stored in refrigerated conditions. During storage, oxygen and carbon dioxide concentrations were monitored in the packaging headspace, and microbial numbers in the tofu were assessed. Substantial amounts of oxygen (O2) were deliberated from the tofu during storage, and CO2 was absorbed into the product. Pronounced changes in gas profiles clearly coincided with rapid microbial growth. At 10 days of storage, microbial counts were 1 to 4 log cycles higher in air-packaged tofu compared with tofu packaged in modified atmosphere. At 3 weeks of storage, the counts in modified atmosphere-packaged tofu reached the same level as those in air-packaged tofu. Modified atmosphere packaging as applied in this study was demonstrated to retard microbial growth up to 14 days. PRACTICAL APPLICATIONS Tofu is produced globally in large quantities, but it is highly perishable. This is the first report on the application of modified atmosphere packaging (MAP) for tofu. Our research demonstrates (1) that microbial growth can be retarded by packaging tofu in 30% CO2/70% N2; and (2) that the application of MAP to a food product can be evaluated by repetitive monitoring of O2 and CO2 concentrations in the headspace during storage. For tofu, the O2 and CO2 profiles reveal substantial gas exchanges between product (and its microflora) and headspace. For fresh fruits and vegetables, evolutions in the headspace gas composition during storage due to respiratory activity are known and taken into account in the design of a MAP application. Our findings point out that also for non-respiring products, gas composition changes should be anticipated when developing a MAP application.