MINIMIZING THE RESIDUAL OXYGEN IN MODIFIED ATMOSPHERE PACKAGING OF BAKERY PRODUCTS

The total elimination of air represents a serious hurdle in modified a tmosphere packaging of bakery products, due both to the high spin-rate s of the packaging lines and, particularly, to the typical texture of bakery products which retain large quantities of air inside their poro us structure. Simulating the gas-flushing modified atmosphere packagin g with laboratory equipment and measuring the oxygen concentration dir ectly inside bread rolls, by means of a gas analyser connected with th e internal portion, it was possible to follow the rate of atmosphere s ubstitution, evaluating the effects of different baking treatments (7, 12 and 23 min at 230 degrees C) and the role played by different gase s (nitrogen, argon, helium, nitrous oxide and carbon dioxide). The oxy gen content inside the products, plotted versus time, led to typical l ogistic 'dose-response' curves which made it possible to forecast the time needed to reach established values of residual oxygen concentrati on and to emphasize the effects of the different conditions used. The gas properties particularly affected the rate of oxygen substitution a nd the less water-soluble was the gas, the faster was the oxygen reduc tion, the larger was the gas molecule, the slower was the process. Als o baking time was shown to have, to a different extent, some measurabl e effects on the rate of oxygen substitution and hence, its optimizati on as well as the choice of gas mixture can contribute to improve modi fied atmosphere packaging of bakery products.