Staling of Wheat Bread Stored in Modified Atmosphere

Modified atmosphere packing (MAP) of bread is known to extend the microbial shelf-life. However, the effect of MAP on staling of bread is more questionable, and conflicting results are reported in the literature. To investigate the effect of MAP, wheat bread was packed in modified atmosphere containing 100% CO2and in a mixture gas of 50% CO2and 50% N2, respectively. The control bread was packed in atmospheric air. No significant effects of MAP were found during storage of bread for 7 days at 20°C compared to control bread, when changes in bread firmness and starch retrogradation measured by differential scanning calorimetry (DSC) were used as parameters for the staling rates. In addition, no significant differences were obtained in firmness between bread stored in 100% CO2, and in the mixture gas of CO2and N2after 7 and 14 days, respectively. The present study thus demonstrated that storage of bread in MAP could be used to extend the microbial shelf-life without affecting the staling rate. The development of bread firmness during storage in 100% CO2for 49 days was found to be correlated to amylopectin retrogradation and to changes in the freezable water fraction of the breads in a non-linear manner, suggesting that bread firmness is influenced by both the crystallisation behaviour of starch and by changes in hydration.