Impact of blanching on polyphenol stability and antioxidant capacity of innovative coriander (Coriandrum sativum L.) pastes

Fresh coriander leaves were steam- and water-blanched at 100 °C and at 90 and 100 °C, respectively, for 1–10 min, and subsequently comminuted to form a paste. Pasty products obtained from coriander fruits were processed after water-blanching applying the same time-temperature regimes. Among the 11 phenolics characterised in leaves by high-performance liquid chromatography coupled to mass spectrometric detection, several caffeic acid derivatives, 5-feruloylquinic and 5-p-coumaroylquinic acids were tentatively identified for the first time. In fruits, 10 phenolics were detected, whereas rutin, a dicaffeic acid derivative and two feruloylquinic and caffeoylquinic acid isomers were newly detected. Upon steam-blanching for 1 min, phenolic contents and antioxidant capacities remained virtually unchanged. In contrast, water-blanching and extended steam-blanching even yielded increased levels compared to the unheated control, whereas short-time water-blanching resulted in higher values than prolonged heat treatment. Thus, short-time water-blanching is recommended as the initial unit in the processing of coriander leaves and fruits into novel pasty products.