Maryam Mandegari; Abdol Majid Mirzaalian Dastjerdi; Laleh Mosharaf; Maryam Tatari
Abstract
Introduction: Pomegranate (Punica granatum L.) is an important horticultural fruit that is generally very well adapted to the Mediterranean climate. Arils are the edible part of this fruit, being rich in anthocyanins and bioactive compounds such as phenolic compounds and flavonoids which act as antioxidants ...
Read More
Introduction: Pomegranate (Punica granatum L.) is an important horticultural fruit that is generally very well adapted to the Mediterranean climate. Arils are the edible part of this fruit, being rich in anthocyanins and bioactive compounds such as phenolic compounds and flavonoids which act as antioxidants and free radical scavengers. Susceptibility to chilling injury in pomegranate fruits is a major limiting factor in storing fruits at low temperatures. Below 5 °C, pomegranate fruits show symptoms such as surface pitting, browning, discoloration, and decay. The control of temperature is an effective tool for extending the shelf life of fresh horticultural products. Oxidative stress, as caused by an excess of reactive oxygen species (ROS), is usually associated with chilling injury in fruits. Nitric oxide (NO) is an important gas molecule, the involvement of which in many physiological processes can protect plant cells against oxidative stress by reducing the accumulation of ROS. Postharvest studies have shown that the application of NO gas can extend the storage life of a range of horticultural produce by delaying ripening or senescence. Due to the high number of pomegranate cultivars in Iran, limited amounts of information exist on how the qualitative characteristics of arils in the Malas pomegranate can be affected by nitric oxide and different temperatures during storage. The Malas cultivar comprises a large share of pomegranate exports from Iran. In this research, the positive effects of nitric oxide were examined on reducing the chilling injury and maintaining the fruit quality of pomegranate. The application of this treatment at different concentrations and different storage temperatures led to variable effects on the qualitative characteristics of arils in the Malas pomegranate. Materials and methods: Malas pomegranate fruits were harvested commercially from Isfahan Province and were transferred to the Food Industry Laboratory of Isfahan Natural Resources Research. The fresh arils were separated from fruit tissues and were immersed in solutions of nitric oxide (0, 5 and 10 μM/L) for 5 min. After draining, the arils were placed in packaging films of polyethylene and were immediately stored at 2, 4 and 8 °C for 21 days. Several parameters were measured every 7 days during the storage time. These were the weight loss, total soluble solids, titratable acidity, TSS/TA, acid ascorbic, total phenol, total anthocyanin content, antioxidant activity, MA, ion leakage, POD, PPO activity and sensory evaluation. The current study was carried out as a factorial assay and was based on a completely randomized design with three replications. Data were processed by ANOVA using the SAS software version 9.4. Significant differences were identified using Duncan’s test at 1% probability level. Results and discussion: Results showed that the total anthocyanin content, total phenol, antioxidant activity, and titratable acidity decreased during storage time. The control group and the treatment with low temperatures significantly reduced the qualitative characteristics of arils during storage. The water content of arils treated with 5 and 10 μM nitric oxide was maintained considerably for 21 days during storage. According to these results, unlike titratable acidity and ascorbic acid which decreased in both treated and untreated fruits, there was an increase in the total soluble solids and POD activity of arils during storage. However, nitric oxide reduced the rate of these changes, whether it be the decrease or increase in the measured parameters. During the experiment, the control samples showed lower values of quality regarding all parameters. The use of nitric oxide in fruits reduced lipid peroxidation and ion leakage significantly, whereas the antioxidant activity increased. The decrease in ion leakage was observed most notably in fruits that were treated with 10 μM nitric oxide. Furthermore, low temperatures managed to disrupt the metabolic balance of reactive oxygen species, leading to the accumulation and destruction of antioxidant enzymes. In the present study, exogenous treatments with nitric oxide at 5 and 10 μM significantly reduced the lipid peroxidation content and electrolyte leakage of arils being stored at cold temperatures, compared to untreated arils. Nitric oxide suppressed the activity of polyphenol oxidase (PPO) and preserved the physical appearance and the internal quality of pomegranate arils. The decrease in phenolic compounds (29.32%) and antioxidant activity (39.91%), besides the increase in lipid peroxidation (38.37%) and ion leakage (36.98%), caused deteriorations in the appearance and organoleptic properties of the control samples. To alleviate these problems, nitric oxide has beneficial effects on maintaining the anthocyanin content of pomegranate arils by partially inhibiting PPO enzyme activity during storage. It prolongs the postharvest life, helps to preserve the quality of pomegranate arils, suppresses the formation of ethylene, reduces the respiratory rate and controls weight loss, in addition to maintaining the firmness of fruits. Delaying the changes in peel color and TSS are also considered as useful effects of nitric oxide on pomegranate arils. Nitric oxide impeded the process of senescence by slowing down PPO-related activities, thereby maintaining the total phenolic content of pomegranate arils.In conclusion, the application of nitric oxide was observed to reduce ion leakage and PPO activity in pomegranate arils, while also maintaining the quality of arils. Ultimately, the use of 10 µM nitric oxide at 8 °C can be suggested as the most optimum treatment herein.
Maryam Hashemi; Abdol Majid Mirzaalian Dastjerdi; Ahmad Shaker ardakani; Seyed Hosein Mirdehghan
Abstract
Introduction: Pistachio is one of the dried and native products of Iran, which has a special economic and export significance due to its excellent quality. Pistachio kernel is rich in unsaturated fatty acids; therefore, its unsaturated fatty acids can tolerate oxidation and, as a result, change the flavor ...
Read More
Introduction: Pistachio is one of the dried and native products of Iran, which has a special economic and export significance due to its excellent quality. Pistachio kernel is rich in unsaturated fatty acids; therefore, its unsaturated fatty acids can tolerate oxidation and, as a result, change the flavor of the product. Various factors, such as temperature, relative humidity, light, etc., affect the storage of many nuts. During pistachio storage, the lowest rate of oxidation and hydrolysis occurs in low humidity and under the carbon dioxide atmospheric. Therefore, packaging with low-permeability plastic films, in a dry product with a moisture content of less than seven percent, can be a good way to maintain product quality. Pistachio packaging depends on several reasons include physical protection of the product, preventing product spoilage, attracting customers, preventing aflatoxin contamination, and ensuring a high-quality, healthy consumer product. Considering the high nutritional value of pistachios and its importance for exports, research is needed to improve the storage and the availability of a healthy, quality product. Therefore, in this research, the role of plastic coatings with different materials and layers on the shelf life and maintaining the nutritional value of dry pistachios was investigated.
Materials and methods: In this experiment, dry commercial Ahmad Aghaei pistachio cultivar was used. 200 grams of intact fruit was placed in plastic bags of different materials and then sealed with thermal sewing. Finally, the packages were placed at 20 ± 3 ° C. Polymeric coatings used include uncoated (control), single layer polyethylene plastics (PE), dual layer plastics with metallized polyamide composition, and extruded polyethylene (PA- ONM / PE ex), three layer plastics by combining polyester, polyurethane and polyethylene (PEs / Pu / PE), three layers of plastics with cast polypropylene, polyurethane and polyester composition (CPP / Pu / PEs), five layers plastics with polyamide, Ethylene vinyl Alcohol, two layers of extrusion and polyethylene plastics (PA / EVOH / Tie / Tie / PE), seven layers of plastics with polyethylene, two layers ethylene vinyl alcohol, two layers of extrusion bonded polymer, polyamide and extruded polyethylene (PE / EVOH / EVOH / Tie / Tie / PA / PE ex). The desired traits (weight loss, kernel hardness, peroxide value, free fatty acid, soluble sugars and sensory evaluation) was measured before the treatments and after 2, 4, 6, 8, 10 and 12 months of the storage period. The experiment was carried out in a factorial arrangement in a completely randomized design with three replications. Statistical analysis of the data was performed using SAS software version 9.1.3 and comparisons of the meanings by Duncan's multiple range test at a probability level of 1 percent. Drawing of the diagrams was done using Excel software.
Results and discussion: Pistachios packed with seven-layer and double-layered coatings showed the least weight loss and kernel hardness in the packaging due to the polymeric coating. Plastic coatings play an important role in preventing weight loss by creating a saturated micro-atmosphere around the fruit, and probably due to less moisture loss (less weight loss) in these packaging coatings, the hardness of the kernel was also lower than other materials. Also, during the storage period, the amount of peroxide value and free fatty acid in the control and the various types of packaging coatings increased, but this increase in the package with two and seven layers of slope was slower than the control and other materials. Double-layered and seven-layered treatments in comparison with control and other coatings had significantly lower peroxide value and free fatty acid content. In the tenth and twelfth months, the treat of (1.6) and seven layers (1.93) compared with control (10.4) and other coatings had significantly lower peroxide value. Also, at the end of the storage period (12 months), polyethylene (1.54), uncoated treatment (1.22) and tree layer packaging (CPP / PU / PEs (1.08) showed more free fatty acid content compared to other types of packaging. The most important degradation reaction that results in reduced product quality during the storage period is the radical oxidation mechanism and the formation of hydroperoxides. The main reason of kernel rancidity in nut packagings is inappropriate sewing of packages and the penetration of oxygen into the package. In the present study, two-layer and seven-layer packaging films showed less free fatty acid due to their low permeability to oxygen and moisture compared to other coatings. According to the results of other reports, it is likely that the higher peroxide value in unpackaged or packaged fruits in this study will be related to the presence of oxygen in the pack, which leads to an exacerbation of fat oxidation and the release of hydroperoxides. The influence of gases and light in the package, causing adverse changes in appearance and accelerating chemical reactions, as well as the presence of oxygen inside the package, also accelerates the oxidation reaction. Therefore, so the packaging type and the atmosphere inside it are two factors determining the shelf life of pistachios and the decrease score in texture, tastes, flavors of nuts during storage can be due to the absorption of moisture by nuts and the oxidation of fatty acids which affect the texture, taste and flavor. The coating used in this study showed better sensory parameters than the control.
