Effect of modified atmosphere packaging on the microbial and sensory properties of Rogen bread

Rogen bread is one of the loaf bread, with a relatively short shelf life. In this study, the effects of different modified atmosphere packaging (MAP) on moisture content, microbial changes and sensory properties of rogen bread during five days storage were investigated. Bread was prepared using the formulation presented by Sahar Bread Factory and immediately transferred to the packaging lab. Breads were packed after being transferred to the laboratory by a packaging machine designed to form headspace and injected into polyamide polyethylene bags, then the qualitative characteristics of the bread included, microbial and sensory storage were maintained for five days (In the first, third and fifth days of storage, the room conditions (25 ° C and relative humidity (38 ± 2%) were tested. In this study, sensory analysis of bread was evaluated through parameters such as crust rupture, shell color and texture color, flavor, internal wall porosity, tissue porosity, chewing ability, form and shape of the bread, and ultimately overall sensory score.Head space gases in the present study included: air (control), 100% N2, 100 CO2%, 70% N2:30% CO2, 30% N2:70% CO2, 50% N2:50% CO2 were tested at ambient conditions (25 °C and 38±2% RH). The results of the study showed that, by increasing the storage period, increase in moisture content was observed in all the samples, control had the highest change, and gas combination treatment had the lowest change. In the present study, in all treatments, the moisture content of bread crust increased until the third day (Table 2), and there was no change in the majority of treatments until the fifth day (except for control treatment and 100% nitrogen treatments). This phenomenon is related to the difference in moisture content between the crumb and the crust, which, as a driving force, results in the migration of moisture from the crumb to the crust and ultimately into the surrounding environment. Over time, the reduction in this difference leads to a decrease in the rate of loss of moisture (Piazza and Massey 1995). The results of changes in the total count of microorganisms in Table 3 showed that the total count of microorganisms in the control treatments and treatments of 100% carbon dioxide and 100% nitrogen in the first day was log CFU /g. Nitrogen and carbon dioxide combinations were not observed in microorganisms during the whole period of storage. The gases used in the modified atmosphere, such as carbon dioxide, have antimicrobial properties, and its mechanism is that it dissolves into the water and produces carbonic acid, which carbonic acid is introduced from the cellular membrane of the microorganism and into the cell It is ionized and by interrupting the electrical balance inside the cell causes the death of microorganisms. The other reason for the reduction of microbial growth in modified atmospheric samples is the absence of oxygen in these packages, in addition to the antibacterial and antifungal effects of carbon dioxide, in addition to the antibacterial and anti-fungal properties of carbon dioxide (Sortsev et al. 2002; Orekole 2003). The results of this study were consistent with the results of studies by Conver et al. (1985), Fernandez et al. (2006) and Dergmynchuklu et al. (2011). Results of changes in mold and yeast in Table 4 showed no control except for the remaining treatments during the whole period of mold and yeast storage, and on the first day, the mold and yeast content were zero in control treatment but significantly increased with increasing time Found (P <0.05). Some other researchers investigated the use of modified atmosphere packaging (MAP) to extend the shelf life Iranian flat bread including Barbari and Sangak breads. Four treatments of atmospheres including 100% CO2, 70% CO2 – 30% N2, 30% CO2 – 70% N2 and normal air were used. Results showed that it is possible to prolong the shelf life of breads to about 17 days by using modified atmosphere packaging with high carbon dioxide concentration and high-barrier laminated. However, significant differences (P<0.05) were obtained in the firmness of control bread compared to another treatment. It seems that, modified atmosphere packaging including 50% N2:50% CO2) and 30% N2:70% CO2, respectively cause better quality of rogen bread than other conditions during storage.