Distribution of almond polyphenols in blanch water and skins as a function of blanching time and temperature

Abstract

The distribution of polyphenols in blanched almond skins and blanch water, as a function of time and temperature, was quantified using negative ion electrospray time-of-flight mass spectrometry (ESI TOF MS). Almonds were blanched in 25° (RT) and 100°C (HW) water for up to 10min. At 10min, ∼30% (25°) and 90% (100°C) of the polyphenols quantified had leached from the skins into the blanch water. Many of the compounds precipitated from the blanch water due to limited water solubility, as evidenced by a logarithmic fit to kinetic data (1st order kinetics). The rate of procyanidin degradation into smaller polymeric units (e.g., catechin and epicatechin) also increased as a function of time and temperature. Finally, hydration in RT water increased the extraction efficiency of phenolics by 25%. This work shows that the blanch water, in particular the 100°C blanch water, was rich in polyphenols and supports exploration of alternative uses for blanch water.