Investigation and dynamic changes of phenolic compounds during a new-type fermentation for ripened Pu-erh tea processing

Abstract

At present, several novel pile-fermentation styles have been developed for ripened Pu-erh tea (RPT) processing. In this study, tea pigments, phenolic compounds, purine alkaloids and amino acids in six RPTs produced through three various fermentation styles were determined by using HPLC and amino acid analyzer to reveal chemical differences caused by fermentation style, respectively. Additionally, dynamic changes of phenolic compounds and purine alkaloids were explored during a whole new-type fermentation. Despite three various fermentation styles, these RPTs demonstrated consistent sensory and major quality components including three tea pigments, two flavonoids and three purine alkaloids. However, RPTs of the new-type fermentation had relatively higher contents of seven catechins, gallic acid, two flavonols (i.e. quercetin and kaempferol), two other flavonoids (i.e. rutin and luteolin) and 10 amino acids such as l-theanine and l-arginine. The new-type fermentation decelerated the degradation of four galloylated catechins, rutin, amino acids and soluble sugars, but contributed to the accumulations of three non-galloylated catechins, two flavonols, luteolin and gallic acid. Therefore, the new-type fermentation could be a potential style for RPT processing with a shorter fermentation cycle.