Dynamics of Water-soluble Pectin in the Roasting Process during Green Tea Manufacturing

Abstract

We examined changes in water-soluble pectin (WSP) and dilute hydrochloric acid soluble pectin (HSP) contents of tea leaves, and pectin content of tea infusions in the roasting process during refined tea manufacturing by crop season. In all crop seasons, WSP content in tea leaves increased with roasting temperature. HSP content was almost constant or increased with roasting temperature by crop season. Changes in pectin content of tea infusions by roasting temperature were proportional to or lagged slightly behind WSP content changes of tea leaves in all crop seasons. In all crop seasons, the molecular weight (MW) distribution of both WSP in tea leaves and pectin in tea infusions was biased toward the lower-MW range with increasing roasting temperature. In parallel, major peaks in the MW distribution of pectin in tea infusions shifted to the lower-MW range in all crop seasons. It was postulated that β-elimination degradation was involved in WSP production from water-insoluble forms of pectin in HSP and the degradation of WSP itself during the roasting process.