Effect of the Drying Method and Optimization of Extraction on Antioxidant Activity and Phenolic of Rose Petals.

The effect of freeze and hot air drying methods on the retention of total phenolics, antioxidant activity (AA), and color of different cultivars of rose petals was analyzed. Both methods similarly preserved the phenolic content and AA, while freeze drying showed better red color retention. Furthermore, the conditions of total phenolics and AA extraction from two rose cultivars, Lovely Red and Malu, were optimized by response surface methodology through a Box-Behnken design. The solvent exhibited a major effect on the total phenolic content (TPC) and AA. The selected parameters were ethanol 38%, 75 °C, and 30 min. Under these conditions, the predicted values for Lovely Red were 189.3 mg GA/g dw (TPC) and 535.6 mg Trolox/g dw (AA), and those for Malu were 108.5 mg GA/g dw (TPC) and 320.7 mg Trolox/g dw (AA). The experimental values were close to the predicted values, demonstrating the suitability of the model. Ultrasound-assisted extraction increased the AA of the extracts but not the TPC. Fifteen compounds were identified in the Lovely Red cultivar, with no differences between the two drying methods. The results obtained suggest that the analyzed cultivars, particularly the red ones, can be considered a natural source of powerful antioxidant compounds.

Growing location and root maturity impact on the phenolic compounds, antioxidant activity and nutritional profile of different sweet potato genotypes.

This study aimed to analyze the phenolic compounds, antioxidant activity, and the main nutritional components of different colored-fleshed sweet potato genotypes grown in Argentina. Three cultivars of standard size were compared to undersized ones, currently discarded. Furthermore, four genotypes grown in different agroecological locations in Tucuman, Argentina, were evaluated. Chlorogenic and 3,5-dicaffeoylquinic acids were identified as the prevailing phenolic compounds in all samples. Undersized roots had significantly higher phenolics, antioxidant activity and carotenoids than standard. Therefore, they can confer healthy attributes to processed foods and, additionally, reduce waste. Genotypes from Tucuman grown under water stress conditions presented the lowest phenolics, anthocyanins and antioxidant activity, but the highest carotenoid contents. Orange-fleshed cultivars showed the highest protein percentages (6.0-11.7 %) and carotenoid contents ranging between 310 and 1012 µg ß-carotene/g dw, with more than 90 % ß-carotene. These findings could help to promote the cultivation of local genotypes with high added value.