مهشید غفوری

The present research was conducted to investigate the efficacy of preharvest NaHS application as foliar spraying on the quality and antioxidant capacity of kiwifruits cv. Hayward during cold storage. In the present investigation, the effects of a preharvest treatment with H2S donor NaHS in four levels (0, 0.5, 1 and 1.5 mM) at 110, 125, and 140 days after full bloom on nutritional quality and antioxidant capacity of kiwifruit (Actinidia deliciosa 'Hayward') were evaluated during 90 days of storage at 1 °C and 90% relative humidity. Sampling was done to measure the desired traits during four periods of 0, 30, 60 and 90 days after storage. The results showed that NaHS treatment had a significant effect on the evaluated traits. At the end of 90 days of storage, NaHS treatment prevented fruit weight loss and maintained fruit firmness in comparison to the control. The percentage of electrolyte leakage and the amount of accumulated malondialdehyde (MAD) in all concentrations of NaHS was lower in comparison to the control. Preserving ascorbic acid content and increasing the activity of phenylalanine ammonialyase (PAL) lead to higher production of total phenol and flavonoids and improve the antioxidant capacity of fruits. NaHS treatment decreased the activity of polyphenol oxidase in comparison to the control. NaHS at 1.5 mM showed the best effect among the applied treatments. According to the obtained results, this concentration can be recommended as a suitable treatment to maintain the quality of kiwifruit cv. Hayward.

 Nowadays, the application of chemical compounds is limited due to their harmful effects on human and the environment health. The benefits of seaweeds as sources of organic matter and fertilizer nutrients have been known to agriculture for centuries, especially in coastal areas extracts of these seaweeds have been used for decades as foliar- and soil-applied treatments in crop production systems due to the presence of a number of plant growth-stimulating compounds. Unlike chemical fertilizers, extracts derived from seaweeds are biodegradable, non-toxic and non-hazardous to humans, animals and birds. Therefore, it is required to find a safe compound that is utilized in the postharvest technology of fruit and vegetables. Pre-harvest application of nutrient solutions such as seaweed increases the quality and quantity of crop and also enhance their storage life and marketability. Various researchers reported that aqueous extracts of seaweed increased the yield and quality of tangerine and orange, strawberry, grape, apple, and watermelon fruit. Thus, the aim of the current study was to investigate the effect of pre-harvest foliar application of Seaweed extract on quality and quantity values, antioxidant properties, and storage life of kiwifruits.

 This experiment was carried out on 10-year-old kiwifruit vines, in a commercial orchard located in Gilan Province. Vines were selected with uniform size in terms of growth, yield and fruit load, then sprayed with seaweed extract at four levels of 0, 1, 2 and 3 g.l-1 as a foliar spray and control vines only received water. Foliar spraying was performed in three stages, (110, 125 and 140 days after full bloom stage) and Tween 20 was used as a surfactant. This experiment was designed as factorial based on randomized complete block design with three replications. The fruits were harvested in November with soluble solids content (TSS) of 6.5-6.2% and then transferred to the post-harvest physiology laboratory of the University of Zanjan. The treated fruits were stored for 90 days at 1 ° C with 90% RH. Sampling was done at harvest time and after 30, 60 and 90 days of storage and some quantity and quality traits such as weight loss, tissue firmness, TSS, ascorbic acid, total phenol and flavonoids, antioxidant capacity and the activity of superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL) enzymes were evaluated.

 The ANOVA results showed that seaweed extract, storage time, and interaction of seaweed extract × storage time had a significant effect (p≤0.01) on evaluated traits. All treatments maintained the antioxidant capacity, total phenol and flavonoids content and PAL activity at a higher level compared with control. The amount of fruit tissue firmness, TA and ascorbic acid decreased by increasing the storage time, and at the third month of storage, the lowest amount was observed in the control fruit. Also, comparing the interaction of the mean of treatments and storage time showed that pH, weight loss, TA, TSS, antioxidant capacity, total phenol, flavonoids and PAL enzyme activity increased by increasing the storage time. At the end of the storage time, the highest level of TSS, weight loss and pH were observed in the control fruit. The lowest antioxidant capacity (48.14 %) was observed in the control treatment at harvest time and the highest antioxidant capacity was observed in 3 levels of brown algae extract treatment at the end of storage period. Comparison of means showed that at the first 30 days of storage, the highest PAL enzyme activity was observed in the treatment of 3 g / l of brown algae. PAL enzyme activity significantly increased after the experiment. At the end of storage period, the lowest PAL enzyme activity was observed in control fruit. Treatment of 3 g / l brown algae had higher PAL activity. PAL, as a key enzyme in phenylpropanoid metabolism, catalyzes the conversion of phenylalanine to trans-cinnamic acid, which is the first step in the biosynthesis of phenylpropanoids and leads to the production of secondary metabolites such as lignin, phytolaxoids, and flavonoids. The direct and positive relationship of this enzyme with the synthesis of phenols and flavonoids has been discovered in the fruits of blood orange, strawberry and blueberry. The results of the comparison of the mean showed that the total phenol and flavonoids increased by increasing the storage time. The lowest phenol (23 mg GAE.100 g-1 FW) was observed in control fruit at harvest and the highest (8.88 mg GAE.100 g-1 FW) content of total phenol was observed in 3 levels of brown algae extract at the third month of storage. Plants release phenolic compounds in response to some messenger compounds that play an important defense role. Studies show that there is a positive relationship between total phenol content and their antioxidant activity. Flavonoids are also polyphenolic compounds and are the most important secondary compounds of plants. Under oxidative stress, in plants, the activity of propanoid pathway increases, especially the pathway of flavonoids biosynthesis. Flavonoid compounds are abundant in plants and show antioxidant activity. Seaweed extract enhances the antioxidant capacity of the fruit and thereby inhibits oxygen-free radicals Treatment of 3 g/l seaweed extract had the best effect among the treatments applied in maintaining firmness, fruit weight loss, TA, antioxidant capacity, total phenol and flavonoids and PAL enzyme activity. All three levels of seaweed extract increased the amount of total phenol, flavonoids and antioxidant capacity all over the storage time, but no significant difference was observed among the treatments levels. Based on the results, the application of 3 g/l seaweed extract effectively increased the antioxidant capacity and PAL enzyme activity during 90 days of storage time. As a result, seaweed extract treatment had positive effects on maintaining the quality and increasing the shelf life of kiwifruit during 90 days of storage.

Seaweed extract is one of the natural compounds and compatible with human health and nature has medicinal and nutritional value that can increase the shelf life and maintain fruit quality in the postharvest period. In summary, foliar application of seaweed extract has a significant effect on fruit firmness, total soluble solids, total acid, vitamin C, phenol and total flavonoids, total antioxidant activity and the enzyme phenylalanine ammonialyase. The appropriate treatment for kiwifruit cultivar ‘Hayward’ is introduced. Among the applied treatments, 3 g/l of seaweed extract had the best effect on firmness (40.40%), fruit weight loss percentage (41.87%), titratable acid (25.37%), vitamin C (33.26%), antioxidant capacity (26.70%), total phenol (81.17%), total flavonoids (103.67%) and PAL enzyme activity (153.75%) compared to the control in 90 days of storage.

Using the essential oils to increase the storage life and quality of horticultural products as a new idea is developed in agriculture. In this context, an experiment was conducted in order to effect of application Essential oils of clove and Cinnamon on maintain quality post-harvest of pomegranate (‘Punica granatum’ cv. Tarom red skin). A split design in time in a completely randomized design with two factors essential oils of cloves and cinnamon each in four levels (0, 500, 1000, 1500 mg per liter) and time in three levels (one month, two months, three months of storage) at 6°C and relative humidity of 85 percent, with four replications. The results showed that with increasing storage period total soluble solid (TSS), anthocyanin, electrolyte leakage, chilling injury, weight loss percent and severity of decay increased. Essential oils by reducing oxidation processes, such as respiration of consumption organic acids in products reduce. The amount of anthocyanin in the fruit treated with essential oil of clove increased more than pomegranates treated with Essential oil of cinnamon. Essential Oils of clove and Cinnamon have a similar effect of chilling injury and decay. Decay of (42.25 percent) in control to (30.75 percent) in the essential oil of cloves 1500 mg per liter decreased in the second month of storage. General, pomegranates treated with essential oils of clove and essential oil of cinnamon have better quality and storage life.

Due to high quality, Iran pomegranate is quite competitive compared to other countries is unrivaled among agricultural products and has great economic importance. Using essential oil is a new idea to reduce postharvest losses and increase the horticultural crop storage life and control of fungal infection. In this context, a factorial experiment based on completely randomized design was conducted to study the postharvest spraying of thyme essential oil on storage life and qualitative characteristics of pomegranate fruit (cv. Tarom red skin)
Pomegranate fruit (cv. Tarom red skin) was prepared and transferred to University of Zanjan, Horticulture postharvest physiology lab. Treatments were included essential oil of thyme at four levels (0, 500, 1000, 1500 mg/l) and the cold time storage (6 °C and 85% of relative humidity) at three levels (one, two and three months (by four replications. In the first experiment, 180 normal pomegranate fruits were treated with thyme essential oil. In the second experiment, fruits were infected with spores of the fungus Aspergillus niger and then treated with essential oil. During experiment, total soluble solids (TSS), titratable acidity (TA), TSS/TA ratio, pH, anthocyanin, electrolyte leakage, chilling injury, weight loss and fungal decay were evaluated. Fruit juice TSS was determined with a hand-refractometer at room temperature. TA was determined by titration an aliquot (20 mL) of the juice with 0.1 N NaOH and the results were expressed as a percentage of citric acid. The maturity index (TSS/TA ratio) was evaluated as the TSS/TA ratio. Fruit juice pH was measured using a pH meter. Anthocyanin was performed to method Fuleki & Francis. Electrolyte leakage was measured according to McCollum & McDonald method. Weight loss was measured according to Ershadi method. Chilling injury was measured by Wang method. Decay was visually evaluated and expressed as percentage. An analysis of variance was used to analyze difference between treatments and the Duncan test was applied for mean separation at p