Applications of different oxygen scavenging systems as an active packaging to improve freshness and shelf life of sliced bread

The objective of this study was to extend the shelf life of sliced sourdough bread by active packaging using oxygen absorbers of different capacity in combination with a modified atmosphere. The sourdough bread slices were packaged using biaxially oriented polypropylene/polyvinylidene chloride (BOPP/PVDC) bags with two oxygen absorbers of different capacity (100 and 300 cc) under different atmospheres (air, 50% carbon dioxide [ CO2]:50% nitrogen [ N2], 100% N2) and stored at 22 °C for 18 days. The high capacity absorbers kept the O2% concentration < 1% in 100% N2 atmosphere during the entire storage. In the headspace containing the high capacity absorber, the initial oxygen (21%) decreased below 1% in six days, and in nine days in the packages with the low capacity absorber. Whiteness index decreased and browning index increased during storage, but the highest whiteness index, lowest browning index and hardness were obtained for 100% N2 combined with the high capacity absorber. The chemical properties were affected by the storage time but not by the packaging treatments. The microbial growth was kept at a lower level in bags with 100% N2 and high capacity absorbers. The study indicated that modified atmosphere packaging (50% CO2 and 50% N2) with no initial oxygen was not sufficient to preserve microbial quality, possibly due to transfer of trapped oxygen from the pores of the sliced bread to the headspace during the storage period. The product packaged with 100% N2 and the high capacity absorber received the highest sensory scores and had the longest shelf life (12 days) among all treatments.