Improved preservation of the color and bioactive compounds in strawberry pulp dried under UV-Blue blocked solar radiation

Strawberry (Fragaria ananassa spp.) is a highly preferred fruit because of its health benefits, flavor, fragrance, and color appeal. The drying process for strawberries extends their shelf life but also changes their color and alters their nutritional contents. The anthocyanins are responsible for the color, which are susceptible to degradation during thermal processing, reducing the customer appeal of these food products. The benefit of solar drying of strawberry pulp using UV-Blue blocking optical filters compared with d irect solar drying is presented in this work. Total anthocyanins, antioxidant activity, and the color of the strawberry pulp were monitored as the drying progressed. The UV-Blue blocking optical filter consisted of a copper sulfide/copper selenide thin film of 160 nm in thickness applied on the outer surface of cellular polycarbonate sheets of 8 mm cell-size, 0.1 mm wall thickness (1 kg/m²) cut from sheets measuring 122 cm x 122 cm in area, and protected by a food-safe adhesive polyethylene foil. Total anthocyanins and antioxidant activity were measured using the differential pH and the DPPH (2,2-diphenyl-1-picrilhydrazil) methods. The filter preserves a higher total anthocyanin content and antioxidant activity in the dried product than in the pulp dried under sunlight conditions. A reduced total color change was observed in the product dried under the UV-Blue blocking solar filter. This study highlights a general need to evaluate the bioactive merits of solar dried farm produce to assess the advantage they hold for their commercialization.