Impact of blanching and frying heating rate/time on the antioxidant capacity and (poly)phenols of cardoon stalks (Cynara cardunculus L. var. altilis DC)

Abstract

This study assessed the influence of blanching and frying heating rate/time on the antioxidant capacity and (poly)phenols of cardoon stalks (Cynara cardunculus L. var. altilis DC). Blanching (98 °C, 30 s) increased the total native chlorogenic acids content (1.2-fold vs raw cardoon), with no significant changes in DPPH antioxidant capacity, but with a decrease in ABTS antioxidant capacity (0.6-fold). Specifically, total di-caffeoylquinic acids (CQAs) increase (1.6-fold) counterbalanced the losses of 5-CQA (0.8-fold). All frying conditions (t85°C = 5, 12 or 10 min, ttotal = 15, 15 or 30 min, respectively) decreased the antioxidant capacity (0.5–0.7-fold in DPPH, 0.5–0.9-fold in ABTS) of cardoon, but increased total flavonoid amount (3.6–3.7-fold) that remained at low levels. The Short (15 min) and Intense-heat Frying (t85°C = 5 min) favoured the release of chlorogenic acids, particularly 5-CQA, from the food matrix. However, a longer frying process (30 min) induced an almost complete degradation of di-CQAs. Thus, it is desirable to limit the frying duration. When blanching and frying were combined, a higher thermal degradation of (poly)phenols was observed, but the Short and Intense-heat Frying remained the most suitable. This study highlights the importance of selecting optimal culinary conditions for vegetables that favour a high content on bioactive compounds and, therefore, their potential healthy properties.