فعالیت آنتی اکسیدانی سیب ̓ رد دلیشز، تحت محلولپاشی قبل از برداشت اسید فرولیک و نانوکیتوسان

Apple (Malus domestica) are a crucial part of human nutrition because of their rich content of phenolic compounds and high antioxidant capacity. During the development stage, it accumulates various beneficial compounds like sugars, organic acids, vitamins, fibers, and antioxidants, all of which are highly valued by consumers. The concentration of these compounds can be influenced by several factors, including climate, genetic (variety), orchard management, harvesting methods, and storage and processing conditions. Given that high quality is a significant factor for consumers, extensive research has been dedicated to developing new techniques for preserving and maintaining the optimal organoleptic characteristics of fruits. Currently, consumers demand more natural and environmentally friendly food products, with high quality and longer shelf life, without any chemical preservatives. Achieving these goals together challenges scientists to develop new food preservation strategies. One promising strategy involves the application of edible layers made from polysaccharides and lipids, which can serve as edible coatings. Chitosan has emerged as a particularly popular biopolymer and a leading stimulatory molecule for plants over the past decade, owing to its diverse properties. Ferulic acid is one of the most abundant phenolic acids in plants that acts as a binding agent in the cell wall. Therefore, the aim of this study was to investigate the effect of pre-harvest application of ferulic acid (a phenolic compound with immune system induction properties) and nano-chitosan (a modified oligosaccharide with resistance induction and absorption enhancement effects) on the antioxidant properties of apple fruit.Materials and Methods: This study was conducted on an apple orchard (Malus domestica) in Zarabad area of Khoy city located in the northwest of Iran, which has a moderate climate and mountainous in 2018-2019. The characteristics of the trees studied were as follows: trees with seed rootstock, modifild lidear, and approximately12 years old. Also, the growth and management conditions were the same for all trees. The experiment was conducted as a factorial experiment in a randomized complete block design with 4 replications. The experimental factors included foliar spraying of fruit trees with nanochitosan at 3 concentrations (0, 5 and10 ml L-1) and ferulic acid at 3 concentrations (0, 0.5 and1 mM). Foliar spraying was carried out at three times, the first stage at the time of fruit diameter becoming hazelnut-shaped, the second stage 20 days after the first stage and the third stage 20 days after the second stage foliar spraying, and in total, foliar spraying of treatments was carried out without Tween 80. The control treatment in this experiment was distilled water with Tween80 (0.1/v/v). Finally, the fruits were harvested in October and with the color change index and fruit texture firmness. The harvested fruits were packaged and labeled and transferred to the Central Laboratory of Horticultural Sciences, Urmia University. After24 hours of storage at laboratory temperature, the measurement of the studied traits on the fruits began. To prepare nanochitosan solutions, nanochitosan was prepared in ready form with a particle size of100 nm. Nanoparticles Chitosan (1g) was dissolved in1% acetic acid. The 100 ml of distilled water was added to the above solution and stirred until complete dissolution. In the next step, the pH of the mixture was adjusted with 1 M NaOH solution. Then, different concentrations of chitosan nanoparticle suspensions were prepared for field testing.

Results and Discussion: In this study, the highest total phenolic and flavonoid contents were obtained at high concentrations of chitosan and ferulic acid. Therefore, the use of high concentrations of these compounds can increase the phenolic compounds of apple, which are strong antioxidants. In addition, these compounds act as anti-stress and anti-aging agents in the fruit by scavenging free radicals, which leads to an increase in post-harvest life and maintenance of fruit quality. The antioxidant capacity of fruits treated by nanochitosan and ferulic acid after fruit harvest showed a significant increase compared to the control treatment. It seems that field and pre harvest applications of ferulic acid have not been studied for their antioxidant activity, however, it is expected that ferulic acid, due to its antioxidant properties, will increase the antioxidant activity of fruits. Although there is a clear relationship between antioxidant activity and total phenolic content in this study. The highest polyphenol oxidase activity was observed in the control treatment. Ferulic acid inhibits the polyphenol oxidase activity of the samples and this enzyme does not use the available O2. In the present study, both nanochitosan and ferulic acid significantly inhibited the activity of polyphenol oxidase. Thus, the use of high concentrations of nanochitosan and ferulic acid effectively prevented the browning caused by polyphenol oxidase and reduced the activity of this enzyme, which oxidizes phenolic substrates. In this study, catalase enzyme activity decreased with increasing concentrations of nanochitosan and ferulic acid. Phenolic compounds, including ferulic acid, play an important role in inhibiting reactive oxygen species, inhibiting lipid peroxidation, stabilizing cell membranes, and reducing abiotic stresses. by increasing ferulic acid concentration, the amount of gallic acid decreased and chlorogenic acid increased, while nanochitosan caused an increase in gallic acid and various changes in caffeic acid. Also, the highest amount of apigenin was observed in the combination of 10 mL/L nanochitosan and 1 mM ferulic acid.Conclusion: Therefore, the use of combined treatments of nanochitosan and ferulic acid is recommended, especially in organic orchards, to improve the nutritional quality of apples. Because it reduces crop losses, it can be an economical way to export apple fruits during the season and at good market prices.