Direct Solar Oven with and without UV Filter vs. Traditional Oven: Effect on Polyphenolic Antioxidants, Vitamins and Carotenoids of Food

The use of efficient solar ovens can be a way for progressing ecofriendly technologies in the field of food preparation. In most performing direct solar ovens, the sun rays reach the foods directly, therefore, it becomes essential to check whether, in these conditions, foods can retain theirnutraceutical properties (antioxidants, vitamins and carotenoids). In the present research work, to investigate this issue, several foods (vegetables, meats, and a fish sample) were analyzed before and after cooking (traditional oven, solar oven, and solar oven with a UV filter). The content of lipophilic vitamins and carotenoids (analyzed via HPLC-MS) and the variation of total phenolic content (TPC), and antioxidant capacity (via Folin-Ciocalteu and DPPH assays) have evidenced that cooking with the direct solar oven allows to preserve some nutrients (i.e., tocopherols) and, sometimes, to enhance nutraceutical properties of vegetables (for example, solar oven-cooked eggplants showed 38% higher TPC compared to electric oven cooked sample) and meats. The specific isomerization of all-trans-β-carotene to 9-cis was also detected. The use of a UV filter is advisable to avoid UV drawbacks (for instance, a significant carotenoid degradation) without losing the beneficial effects of the other radiations.