Study On γ-Aminobutyric Acid Pu-Erh Tea

γ-Aminobutyric acid (GABA) acts as a major inhibitory neurotransmitter in thecentral nervous system and is a multifunctional molecule that has different situationalfunctions in the central nervous system, the peripheral nervous system, and in somenonneuronal tissues. GABA has various physiological functions in animals andhumans, such as neurotransmission and induction of hypotensive, diuretic andtranquilizing effects. GABA tea or Gabaron tea which contains more than150mg ofGABA per100g of tea has the potential health benefits of both tea and GABA. It isfor these reasons that GABA tea has become popular in Asia, and GABA green tea,GABA oolong tea and GABA black teas are now being mass-produced andcommercialized in Japan and China. However, there is no GABA Pu-erh tea. Theproduction of GABA Pu-erh teas was studied in this Master Thesis; andGABA-enriched Pu-erh raw teas were developed; the fermentation of Pu-erh tea byinoculation of GABA-producing yeast was preliminary investigated, as well as. Themajor results as follows:1. To conveniently detect GABA during tea producing. A thin layer chromatography(TLC) method was developed after optimizing the experimental conditions, such asdeveloping agents, color agents, the detection limit and the concentration of standardsamples. Glutamic acid and GABA could obviously separate with the developingagents ratio of n-buoh：glacial acetic acidwater at4：2：1,0.4%. The developing agentis ninhydrin, and the limit of detections is0.3μg. GABA levels of50processingsamples were detected using this TLC method. The results of TLC determination wereverified by HPLC. And this verification showed this TLC method can be used todetect the content of GABA during tea producing, it is suitable for quality control ofGABA tea processing.2. A processing technology for GABA-enriched Pu-erh raw teas were developedthrough a series optimized studies including time of anaerobic treatment, spreadingtime, and tea cultivar. The processing technology as: fresh leaves (Yunkang10)â†'spreading for1hâ†'anaerobic treatment by nitrogen for6h (0.006MPA)â†'fixing â†'rollingâ†'sun-dryingâ†'compressing to various shapesâ†'dryingâ†'GABA-enriched Pu-erh raw tea. In a total,525.45kg GABA-enriched Pu-erh raw teaswere produced. HPLC determination showed that the contents of GABA inGABA-enriched Pu-erh raw teas are greater than150mg/100g; the mean content is202mg/100g; and the highest content is265mg/100g.3. Chemical analysis demonstrated that the GABA Pu-erh raw teas are enriched teacharacteristic components, such as polyphenols, catechin, caffeine, and amino acids.Sensory evaluation showed that it has a mellow tasting, slightly sweet, and a mildbitter.4. GC/MS revealed that the main aroma compositions in GABA Pu-erh tea arehexadecanoic acid methyl ester, n-hexadecanoic acid ethyl ester, linoleic acid ethylester, flax acid ethyl ester fatty acid esters and palm acid.5. The GABA level in GABA Pu-erh raw tea is greater than150mg/100g, after6month storage. This suggested the GABA Pu-erh raw tea which could keep tis contentin lone time storage.6. To produce GABA fermented pu-erh tea, a lab and pilot plant pu-erh teafermentation inoculated of GABA-producing yeast was developed using the GABAsun-dried green tea or normal sun-dried green tea as raw material, respectively. TheGABA levels were significantly decreasing during both lab and pilot plant pu-erh teafermentation. After fermentation, the GABA content is lower than the GABA tea (150mg/100g) standard with a level of3.28-7.25mg/100g. and the production of GABAfermented pu-erh tea need further study.