Utilization of Silver Nanoparticles Synthesized via Green Methods from Grape Pomace and Leaves in the Active Packaging of Certain Fruits and Vegetables

Grape pomace and leaves are significant byproducts in Turkey, one of the world's leading grape producers. Currently, these wastes are generally used as soil conditioners, organic fertilizers, sources for natural dyes, and preservatives in foods. However, such applications may lead to the waste of value-added products. Grape residues are rich sources of nutrients and bioactive compounds, including polyphenols, dietary fibers, and vitamins, and play a crucial role in the development of value-added functional food properties. In this context, the present study aims to use antimicrobial and antioxidant silver nanoparticles (AgNP) synthesized from grape pomace and leaves in the production of active fruit and vegetable packaging, thereby enhancing product shelf life and quality. In this study, silver nanoparticles were synthesized using the green synthesis method from dried grape pomace and grape leaves. The synthesized AgNPs were mixed with linear low-density polyethylene (LLDPE) at concentrations of 0.5% and 1%, resulting in the production of active packaging films. The first phase of the study investigated the effect of nanoparticle addition on the structural and physical properties of the films. Subsequently, strawberries, black mulberries, artichoke hearts, and ready-made salad products were packaged using the active packaging films and stored at +4°C for 15 days. Physical, chemical, and microbiological analyses were conducted on days 0, 3, 5, 7, 10, and 15 of storage. AgNPs were synthesized from both grape pomace and leaves using the green synthesis method. The synthesized AgNPs were characterized using UV-VIS spectroscopy, FTIR, XRD, TGA/DTA, and SEM techniques. The thermal profile of the AgNPs showed that even at 300-350°C, there was only a 10% weight loss, indicating the AgNPs possessed good thermal properties. SEM images revealed that the nanoparticles, synthesized from grape leaves and pomace, had spherical morphology with sizes ranging between 26.3-55 nm and 33.04-57.1 nm, respectively. The addition of AgNPs improved the mechanical durability of the active packaging films by increasing tensile strength and elongation percentage. It was also found that silver nanoparticle addition reduced the oxygen and water vapor permeability rates of the LLDPE films. The oxygen permeability rate of the 0.5 YP coded films decreased by approximately 17% compared to the control group without nanoparticles. The initial yeast and mold count in strawberry samples was determined to be 3.75 log CFU/g. At the end of the storage period, the highest yeast and mold count (5.37 log CFU/g) was found in the control group, while the lowest count (2.93 log CFU/g) was observed in samples packaged with 0.5% AgNP films derived from grape leaves. The AgNP-added packaging films exhibited antimicrobial effects in the strawberry samples by preventing logarithmic increases and effectively reducing the loss of total phenolic content compared to the control group, thus preserving strawberry quality and freshness. Similarly, AgNP addition was found to be effective in maintaining the acidity of black mulberry samples and extending their shelf life by limiting microbial growth. At the end of the storage period, the control group of black mulberry samples had the lowest total phenolic content (94.94 mg/100 g GAE), while the samples packaged with 1% AgNP films derived from grape pomace had the highest total phenolic content (160.83 mg/100 g GAE). The addition of AgNPs contributed to better preservation of phenolic compounds in black mulberries. In artichoke samples, the greatest changes in a* and b* color values were observed in the control group at the end of the storage period, while the least changes were found in samples packaged with 0.5% AgNP films derived from grape leaves. AgNP addition was effective in maintaining the color and freshness of artichoke samples. Although the total phenolic content of all artichoke samples significantly decreased during storage, the highest loss was observed in the control group (p<0.05). Significant increases in total aerobic mesophilic bacteria (TAMB) counts were observed in control artichoke samples on days 10 and 15 of storage (p<0.05), whereas significant reductions were detected in TAMB counts in samples packaged with AgNP-added films (p<0.05). In the ready-made salad samples, an increase in acidity and a decrease in pH values were observed in the control group on days 10 and 15 of storage. In contrast, the least changes in pH values were found in samples packaged with 0.5% AgNP films derived from grape leaves. It was also determined that the samples packaged with AgNP-added films exhibited less change compared to the control group from the beginning of storage and had the highest antioxidant activity values at the end of the storage period. In conclusion, films with AgNP additions were more effective in preserving the quality characteristics, ensuring microbiological safety, and extending the shelf life of strawberries, black mulberries, artichokes, and ready-made salads compared to the control group. These findings suggest that AgNP-containing films have significant potential for use in food preservation.