Studying the Effect of Modified Atmosphere (MAP) and Storage Time on Some Quantitative and Qualitative Characteristics of Citrus Fruits in Above-Zero Cold Storage

Background and objectives: Methods of preserving fruits and vegetables play an important role in the human food pyramid in order to maintain their quality and freshness. One of the common methods, is modifying the atmosphere inside the package. In this method, the normal air in the environment of the packaged product is removed and, by creating a vacuum, a gas composition proportional to the respiration rate is replaced. In the present study, the effect of modified atmosphere and storage time on some quantitative and qualitative characteristics of oranges and lemons in a cold storage above zero degrees was investigated.
Materials and methods: In this study oranges and local sour lemons were used for modified atmosphere packaging, three-layer polyvinyl chloride plastic bags and a DZQ-400/2E (made in China) packaging machine were used. The samples prepared for each of the two gas mixtures (%10 CO2 + %15 O2 + balance N2) and (%15 CO2 + %10 O2 + balance N2) consisted of 3 lemons and 3 oranges in 3 replicates. The samples were placed in plastic bags and after injecting the appropriate gas mixture and sealing them, they were transferred to the cold storage. All samples were stored in the cold store for 60 days at a temperature of 2 to 4 degrees Celsius and a relative humidity of %85. Quantitative and qualitative quantities such as sample weight, fruit firmness, soluble solids, acidity percentage, and vitamin C content were measured every 15 days. Statistical analysis was performed using SPSS software and graphs were drawn using Excel
Results: The results showed that there was a significant difference between the gas composition of 10% CO2, 15% CO2, the vacuumed sample and the control, but the interaction effect of storage time and modified atmosphere on pH changes was not significant. The weight loss after 60 days was 2.9% in the control sample and 0.29% in the sample with 15% CO2. According to the results, the gas compositions of 15% CO2 and 10% CO2 had a great effect on the preservation of soluble solids, so that the amount of soluble solids in the modified atmosphere with 15% CO2 increased by about 7% for oranges and about 3% for lemons compared to the control sample. The findings indicated that the modified atmosphere coating had a significant effect on reducing the amount of vitamin C during the storage period, but vacuum packaging had no effect on maintaining the amount of vitamin. The firmness of the tissue also increased by %10 for lemons and %7 for oranges in the modified atmosphere compared to the control sample. The results showed that among the modified atmosphere treatments, the best result was obtained with the gas mixture of %10 O2 and %15 CO2.
Conclusion: The results showed that the use of modified atmosphere has a significant effect on all measured indicators and on maintaining fruit quality. The second gas composition had a very small performance better than the other composition, which in general can be considered the same effectiveness of both compositions. The effectiveness of modified atmosphere in orange and lemon fruits was reported to be almost the same. In general, it can be said that the use of modified atmosphere with appropriate gas compositions can play an important role in increasing the storage period and maintaining the physical and chemical quality of the fruit and its marketability and the health of the consumer community.