Grapes are important sources of phenolic compounds, anthocyanins, and ascorbic acid, which are recognized for their significant biological benefits. This study aimed to explore the potential of using a nano zinc oxide coating to preserve the freshness and quality of grapes, as well as the properties of grape molasses. Nano zinc oxide was applied at three different concentrations (0.0%, 0.5%, and 1% w/v) through a three-stage spraying process during the flowering, unripe, and ripening stages, 20 days before harvest. Grape samples were then stored at 4 °C for 35 days. Throughout the storage period, various parameters were measured, including pH, titratable acidity, weight loss, Brix°, total phenolic content, anthocyanin and ascorbic acid levels, antioxidant activity, color indexes (L*, a*, b*), and microbial counts. Also, the properties of molasses were evaluated. Over time, there was an increase in pH (3.58–3.75 to 4.19–4.62), weight loss (0 to 7.12–10.2%), Brix° (22.44– 22.69 to 25.95–28.62), color index b* (20.44–22.18 to 23.01–25.77), total viable count of bacteria (3.24–3.34 to 3.52–3.83 Log CFU/g), and total mold and yeast count (3.06–3.35 to 3.48–3.74 Log CFU/g), while titratable acidity (0.78–0.82 to 0.58–0.67%), phenolic content (1.56–1.88 to 1.29–1.43 mg/g), anthocyanin (0.04–0.05 to 0.03–0.04 mg/g) and ascorbic acid levels (10.03–12.53 to 6.66 to 9.10 mg of vitamin C/100 mL), antioxidant activity (30.06–35.6 to 26.23–29.13%), and color indexes L* (42.91–43.74 to 37.50–39.18) and a* (− 2.10 to − 3.30 to − 3.80 to − 5.36) decreased, along with a decline in sensory scores. By increasing the concentration of zinc oxide nanoparticles from 0 to 1% w/v, total sugar (66.85 to 67.56%) and Brix° (76.93 to 77.5) increased while conductivity (1.80 to 1.53 mS/cm) and specific gravity (1.55 to 1.38 g/ cm3) decreased. The findings indicate that using a 0.5% w/v nano zinc oxide coating is effective in enhancing the freshness and maintaining the quality of grapes during storage.
