Almond by-products: Extraction and characterization of phenolic compounds and evaluation of their potential use in composite dough with wheat flour

Blanched skins and blanching water, by-products of almond processing, were evaluated as potential ingredients of bakery products. The research included three phases: i) optimization of skin drying; ii) optimization of quali-quantitative determination of phenolic compounds, by comparing three extracting protocols; iii) assessment of the impact of by-products on the rheology of composite meals with wheat flour. Besides being less time-consuming, drying at 60 °C for 30 min lowered effectively skin moisture (7.86 g/100 g) and kept better odor notes (leafy and rancid odor scored 6.1 and 0.2, respectively), as well as higher content of phenolics (813.89 µg/g, with the most effective extracting method) and antioxidant activity (81.56 µmol Trolox/g), than sun-drying (8.09 g/100 g moisture; rancid odor scored 6.3; 317.06 µg/g phenolics; 59.23 µmol Trolox/g). Blanching water showed moderate leafy odor (score 3.3), slight sour odor (0.5), negligible rancid odor (0.2), and 917.46 µg/mL phenolics. Dried almond skins altered the alveograph and farinograph indices of dough at doses higher than 3 and 5 g/100 g, respectively, whereas blanching water did not cause significant changes. Therefore, almond skins could be used in products tolerating weak gluten network, such as cookies, whereas blanching water could be added to any bakery good.