Effect of microalgae-based ZnO nanoparticles coating on postharvest quality of organically grown blueberry (Vaccinium corymbosum) fruit

Blueberries are rich in polyphenolic compounds, mainly anthocyanins, responsible for strong antioxidant activities beneficial to human health. However, they are easily perishable after harvest due to microbial proliferation and certain insect pests such as Drosophila suzukii. In this study, a coating of organic blueberries with zinc oxide nanoparticles (ZnONPs), made from the culture supernatant of the marine microalga Phaeodactylum tricornutum, was used to increase their shelf life. Blueberries coated with solutions of 0.5–1.5 g L−1 ZnONPs and uncoated blueberries (controls) were stored at 15 °C for 15 d, and their physicochemical and microbiological properties, as well as the number of eggs, live larvae, pupae and adults of Drosophila suzukii, were determined. Compared to uncoated blueberries, coated blueberries showed lower weight loss and decay, as well as higher levels of ascorbic acid, anthocyanins, phenolic compounds and also higher antioxidant capacity. After a storage period of 15 d, blueberries coated with 1.5 g L−1 ZnONPs were characterized by the absence of aerobic mesophilic flora, molds and yeasts. The in vitro fungicidal effect of ZnONPs at a concentration of 1.5 g L−1 against Penicillium italicum and Cladosporium sp. isolated from decayed blueberries showed high percentages of mycelial growth inhibition of up to 89.9%. In terms of insecticidal activity, ZnONPs concentrations above 0.1 g L−1 significantly inhibited the hatching of eggs and the development of D. suzikii larvae contaminating organic blueberries. At a temperature of 15 °C, the shelf-life of untreated blueberries is only 2 d, but coating them with ZnONPs at a concentration of 1.5 g L−1 extends shelf life to 15 d. Coating organic blueberries with ZnO nanoparticles produced from the marine microalga Phaeodactylum tricornutum offers interesting potential as natural preservatives to improve the quality and shelf life of organic blueberries, paving the way for their application in the fight against post-harvest fruit deterioration in favor of sustainable agriculture. [Display omitted] •Biosynthesis of ZnONPs using supernatants from Phaeodactylum tricornutum.•The ZnONPs coating retained the fruit's nutritional and quality attributes.•ZnONPs coatings reduced microbial load of blueberry fruit.•ZnONPs have demonstrated antifungal activity.•ZnONPs acted as insecticides against Drosophila suzikii.