Bioactivities and sensory evaluation of Pu-erh teas made from three tea leaves in an improved pile fermentation process

Abstract

Two commercial Pu-erh teas, 15-year-old Ta-Huang-In and 25-year-old Ta-Hon-In, were used for screening some species of fungi, yeasts, and bacteria, and six of them were isolated and identified as Actinoplanes aurantiacus, Actinoplanes pallidoaurantiacus, Actinoplanes purpeobrunneus, Streptomyces bacillaris, Streptomyces cavourensis subsp. cavourensis, and Streptomyces cinereus. They were selected for inoculated into the tea leaves (Yun Nan from China, TTES-12 and C. S. Oolong from Taiwan) and fermented for 180 days. The total polyphenols and GABA content, and DPPH radical scavenging effects were determined to examine the tea infusion quality. The samples inoculated with S. cinereus had the highest total polyphenols content and maximum capacity to scavenge DPPH radicals; the highest GABA content was obtained while the sample inoculated with S. bacillaris. Further comparison of these samples with two commercial Pu-erh teas of different ages (Ta-Huang-In, 15-year storage and Ta-Hon-In, 25-year storage) showed that DPPH radical scavenging activity and GABA content of S. bacillaris and S. cinereus fermented tea leaf were higher than these two commercial teas. Sensory evaluation also demonstrated that the taste, flavor, and overall acceptance did not had significant differences between the experimental tea leaves and commercial samples. The present studies revealed that the fresh tea leaves inoculated with the suitable microbes in short period of time will possess a high-quality tea infusion as long-term storage Pu-erh tea.