Use of modified atmosphere packaging to prolong the shelf life of ‘Red-Shahrood’ apricot

Introduction:The cultivar and amount of apricot production in the East Azarbaijan province is about 28% of the total country of Iran and 30.2% of the total apricot is produced in Iran. Due to the perishable nature of apricot, it cannot be kept for more than 2-3 days at room temperature and for several days at low temperature conditions. In Iran, about one-third of horticultural and crop products are lost and destroyed annually. Important factors in increasing postharvest losses of agricultural products can be inappropriately picked up, unpurchased shipping, lack of proper keeping and packaging, and so on. This research was carried out with the aim of developing research on apricot, as well as the development of its export, by increasing the shelf life of apricot. In food packaging, the use of appropriate packaging materials, and minimizing waste and the provision of healthier and safer food products have always been considered. Various packaged packaging technologies have been developed to improve the quality and health of foods. Active packaging technologies provide new opportunities for the food industry. In recent years, the effect of modified atmosphere has been studied on the physiological, biochemical and qualitative properties of fruits and vegetables. One of the physiological effects of modified atmospheres on fruit metabolism is the reduction of respiratory rate during storage, which includes a decrease in carbohydrate metabolism, CO2 production, O2 consumption, and heat release. In climacteric fruits such as apricots, the CO2-rich atmosphere and low O2 levels reduce ethylene production. Therefore, the use of MA can increase the length of storage time of fruits. High concentrations of CO2 are effective in O2 consumption. They act as inhibitors of ethylene activity and prevent ethylene synthesis in some fruits such as apricots, avocados, pears, figs and bananas.
Materials and methods: the study focused on reduce the production of ethylene and increase the shelf life of apricot fruit by studying the modified atmosphere packaging technology. In this project, apricot fruits of “Red Shahroud” cultivar were obtained from “Sahand Gardening Research Station of East Azarbaijan Agricultural and Natural Resources Research Center”. Packaging film of polypropylene was prepared for packing apricot fruits with 0.2 and 0.4 mm thickness from a local store. For gas injection operations, capsules containing oxygen and carbon dioxide gases (food grade) were used. The packets space were first with vacant evacuated, and then gases injected. After the gas was injected, the packages were stored in the refrigerator at a temperature of 1°C (±0.5) and cold air temperatures were kept at about 1 m/s, and every four days, tests were completed that lasted a total of 16 days. The evaluated parameters in this study were TSS, pH, firmness and EC. The MC-20181 model refract meter was used to measure TSS. For pH test, the pH meter of the metrohm-691 model was used. The texture analyser of Hounsfield-H5KS was used to measure the firmness of the apricot fruit. The EC meter ELMETRON CC 505 with an accuracy of 0.1 was used to measure EC. The experimental design was a split plot based on a completely randomized design including two plots and three replications. The main plot consisted of time in four levels (fourth day, eighth day, twelfth day, and sixteenth day). Sub plots was include the type of gas mixture used with different coatings in six levels (3% O2 + 5% CO2 with polypropylene film thickness 0.2 mm, 3% O2 + 10% CO2 with polypropylene film thickness 0.2 mm, 3% O2 + 5% CO2 with polypropylene film thickness 0.4 mm, 3% O2 + 10% CO2 with polypropylene film thickness 0.4 mm, Packaging only with polypropylene cover with thickness of 0.2 mm, Packaging only with polypropylene cover with thickness of 0.4 mm).
Results and discussion: by increasing the storage time, the TSS was increasing. The highest amount of TSS on the 16th day was observed in polypropylene wrap with 0.2 and 0.4 mm thickness without gas composition. TSS represents the presence of small molecules such as glucose, fructose, maltose and some organic acids. By increasing the storage time of fruits, the TSS values will be increased due to the large conversion of molecules such as starch into small molecules such as glucose, maltose and dextrin, as well as reducing the moisture content of the product. On the other hand, due to reduced physiological activity of the fruit at low temperatures, the trend of the TSS will slow down. With increasing storage time, pH increased as a result of the decreasing trend of acidity. Organic acids can be considered as a source of energy stored in fruits, which decrease as a result of increased metabolism activity due to respiration or conversion to sugars. Treatment with only 0.2 mm thick PP coating showed the most effect on apricot fruit acidity, and the rest of the treatments showed an almost identical effect on acidity reduction. The treatment of 3% O2 + 10% CO2 under the cover of PP with a thickness of 0.4 mm showed the highest acidity. With increasing maintenance time, the firmness shows a downward trend. Treatment with 3% O2 + 10% CO2 covered by PP with thickness of 0.4 mm resulted in the highest firmness in apricot fruit compared to other treatments and the least firmness in non-gaseous treatment and only with a thickness of 0.2 mm was observed. With increasing storage time, the EC value also increased, but the effect of different gas constituents with different coatings and the time interaction effect with different gas mixtures with different coatings is not significant. EC shows variations in the resistance or electrical capacity that occurs as a result of changes in the concentration of soluble electrolytes when they are matured in flesh. The EC increases during fruit ripening. The incremental trend of EC extract of fruit during storage is indicative of cation leakage from the cytoplasmic membrane of fruit tissue cells, which shows the degradation of the cell membrane. This process is attributed to the ability of the pectin’s to dissolve and hydrolyse the median wall of the cell. The activity of the polygalacturonase enzyme leads to cell wall pectin hydrolysis, which seems to provide the ability to dissolve the pectin. While the pectin methyl ester enzyme regulates the attachment of cations to the cell wall and the rapid action of other cell wall hydrolysates. Therefore, cations play a key role in enzymatic activity and fruit maturity regulation.
Conclusion: the results showed that with increasing the of storage time, all the traits under test, namely, TSS, pH and EC, increased and fruit firmness decreased. From the point of view of the treatments used, the of type of gas mixture with different films, 3% O2 + 10% CO2 with polypropylene film thickness 0.4 mm treatments is desirable because of increased shelf life of apricot approximately 3 times. Film thickness did not significantly affect the shelf life of apricot fruit.