The Effect of Coating with Pomegranate Peel and Tomato Seedlings Extracts on the Phytochemical Traits and Maintaining the Quality of Strawberry Fruits cv. Paros During Cold Storage

Horticultural waste is one of the top challenges these days. As the population increases, food loss and waste, which has a serious impact on the environment and human health. Horticultural waste is rich in nutrients, polysaccharides and antimicrobial compounds that can be used in the production of edible coatings. Edible coatings protect fruit from nutrient and mineral loss and extend shelf life. Strawberry fruit is one of the commercial horticultural crops because it contains important and diverse sources of natural antioxidants, flavonoids, phenolic acids and minerals. However, the fruit is highly perishable due to its high respiratory rate and metabolic activity, soft texture and lack of protective skin, which can lead to moisture loss, mechanical damage and fungal damage during harvesting, handling and packing. It is estimated that approximately 30% of strawberry fruit is wasted during the post-harvest stage before reaching the consumer. Therefore, reducing the destruction rate of its quantitative and qualitative properties is considered one of the most important challenges. Plant Extract Edible Coating (PEEC) is an environmentally friendly edible coating. Like other edible coatings, PEEC is a thin layer of material applied to the surface of a product. Pomegranate peel extract has biological activities such as antibacterial, antiviral, antioxidant, anti-inflammatory, and antifungal. This extract was used alone or in combination with other post-harvest treatments to preserve product quality. Tomatoes contain secondary metabolites called steroidal glycoalkaloids. These compounds primarily act as crop protection agents against insects, bacteria, parasites, viruses and fungi. This study evaluated the efficacy of pomegranate peel extract and tomato seedlings in maintaining strawberry fruit quality during cold storage and reducing post-harvest waste. 

Healthy fruits with uniform size, shape, and color were carefully selected from strawberries harvested from an orchard in Kamyaran, Kurdistan. We conducted a study to investigate the effects of coating these strawberries with pomegranate peel extract (1%) and tomato seedling extract (1%) on their physiological and qualitative responses. The fruits were coated with the respective plant extracts and subsequently stored at 4 ± 1°C and 90–95% relative humidity for a duration of 15 days. Strawberry quality was analyzed on the first day of storage and on days 5, 10 and 15. Various qualitative factors such as weight loss, firmness pH, total soluble solids content, titratable acidity, total phenolic content, total anthocyanin content, total antioxidant activity, total flavonoid content, ascorbic acid, color and decay severity were evaluated. Statistical analysis of the data was performed using SAS (version 9.4) and mean comparisons were performed using the Duncan multiple range test. 

The study on the property retention and long-term cold storage time of pomegranate peel and tomato seedling extracts coating showed that a concentration of 1% of the extracts used have a significant effect on strawberry fruit quality and phytochemical parameters. It was shown to have a significant impact on strawberry fruit quality and phytochemical parameters, improving compared to the control treatment during cultivation. Weight loss increased with all treatments during storage. After 5 days of storage, no differences between treatments were discernible, but at the end of storage all treatments showed a clear decrease in fruit weight. Pomegranate peel and tomato seedling extracts reduced weight loss by 12% and 15%, respectively, while the control  significantly reduced weight loss by 26%. Despite the decrease in fruit tissue firmness during storage, the firmness of the plant extract-coated fruit was maintained and significantly different from the control. PH remained at low levels for all treatments compared to controls. The total acid and total soluble solids content of the fruit are affected by the treatments considered, the storage, and the combination of times and treatments. The total content of phenolic compounds reached 223 mg gallic acid and 236 mg gallic acid per 100 g fresh weight on the 10th and 15th storage days after treatment with pomegranate peel extract. For tomato seedling extract, this corresponds to 207 mg and 182 mg gallic acid per 100 g fresh weight. The total anthocyanin content in all fruits decreases with increasing storage time, but this trend increases after 10 days when tomato seedlings are treated. In all fruits, various treatments increase anthocyanin levels throughout the storage time. ANOVA of antioxidant activity showed no significant effects on treatment-independent and chronotherapy-interaction effects, while the time-independent effect showed a significant effect at 5%. The greatest antioxidant activity is associated with pomegranate peel extract. The frequency of this feature in treatment decreased with increasing storage time. During the treatment period, there was a progressive increase in antioxidant activity from the 10th to the 15th day, demonstrating a significant difference compared to the beginning of the treatment. Average comparison results revealed a slight but significant difference in the treatments concerning flavonoid content. Analysis of variance and comparison of mean results indicated a significant difference in ascorbic acid content during storage among the different treatments. Color indices remained consistent across all treatments. The 15-day shelf life of strawberries was assessed, and the treatments employed effectively reduced decay rates during storage. Upon analysis, it was determined that the 1% concentration of pomegranate peel extract exhibited the highest efficacy in suppressing the severity of spoilage.

Residues from various agricultural sectors have a variety of uses, including their properties as preservatives that extend the shelf life of perishable fruits and enhance the nutritional value of fruits and vegetables. Replacing plant extracts with synthetic compounds can play an important role in preserving the characteristics and quality of strawberry fruits during storage. Based on the results of this study, an edible coating containing plant extracts from pomegranate peel and tomato seedling as natural preservatives was used to extend the shelf life and enhance the nutritional quality of strawberry fruits during cold storage. Finally, using natural compounds such as plant extracts from agricultural waste is a safe and healthy way to manage and preserve the properties of post-harvest agricultural products.