| γ-aminobutyric acid (GABA) has a variety of biological functions. There are numerous reports about appropriate treatment process could increase the content of GABA in tea processing. Content of GABA in tea above1.5mg/g is called GABARON tea. Considering the functional components and features of mulberry leaf, the mechanism and characteristics of GABA enrichment, this reasearch intends to use mulberry leaves as raw material, studys the effects of processing technology, gas processing and exogenously add on the formation of GABA and quality of mulberry tea. Main conclusions are as follows:(1) The effects of processing technology on the formation of GABA and quality of mulberry tea. Preparing mulberry tea by processing technology of Green tea, studying the effects of spreading, water removing and drying process on the formation of GABA and quality of mulberry tea. The results showed that the mulberry fresh leaves were cutted into4cm×2cm size, Spreading at25～30℃ambient conditions naturally around7h were appropriate, the content of water, aqueous extract, soluble sugar, amino acids, polyphenols and flavonoids were60.5%,43.6%,5.87%,3.11%,3.21%and2.86%, respectively, the content of GABA was0.611mg/g fresh leaves, sensory evaluation results howed that mulberry leaf by spreading has verdant appearance, surface slightly darker leaves, grass gas diminished, the flavor reflected, woody gradually revealed, some leaf quality hard, partly stems off constantly, holding a noise, the surface of the leaves were wilting. Withering leaves were obtained through spreading Process optimization, the content of GABA was0.627mg/g water removing leaf,0.536mg/g water removing leaf and0.567mg/g water removing leaf treated by microwave water removing, Pan fry water removing and steam water removing, respectively. Microwave water removing treatment was better, at this time, the leaves was soft and flexible, gas grass disappeared, aroma appeared, the appearance was verdant, the content of aqueous extracts, soluble sugars and free amino acids of taste quality ingredients were45.78%,5.68%and2.83%, respectively, the content of polyphenols and flavonoids were3.09%,2.84%, respectively.(2) The effects of gas processing on the formation of GABA and quality of mulberry tea. Mulberry fresh leaves were cutted into2cm*4cm size, treated by oxygen, nitrogen and carbon dioxide (fixed concentration of10%) in different proportions(10%oxygen concentration, concentration of carbon dioxide and nitrogen concentration were10%,80%, respectively), and then spreading7h at25～30℃with3-5cm spreading thickness, microwave water removing treatment (water removing time is2min, microwave power is250±50MHz) followed by the first pan-firing and dried (pan-firing temperature and time of100℃and5min; drying temperature and time of90℃and5min) were used to dry the mulberry leaves. The results showed that the content of amino acids, polyphenols and flavonoids were decreased slightly; the content of aqueous extract, soluble sugar and GABA were increased, GABA content reached2.275mg/g dry matter, which was1.86times the levels of GABA in the control group.(3) The effects of exogenously added glutamate, sodium glutamate and aspartate on the formation of GABA and quality of mulberry tea. Mulberry fresh leaves were cutted into2cm*4cm size after adding exogenous treatment, after treating8h by the best atmosphere solution B (10%oxygen concentration, concentration of carbon dioxide and nitrogen concentration were10%,80%, respectively) mulberry leaves were spreaded7h at25～30℃with3～5cm spreading thickness, microwave water removing treatment (water removing time is2min, microwave power is250±50MHz) followed by the first pan-firing and dried (pan-firing temperature and time of100℃and5min; drying temperature and time of90℃and5min) were used to dry the sample. The main factors that affectted the GABA content in mulberry tea was the species of additives exogenous, glutamate> sodium glutamate> aspartate, after treated by A1B2C2(spraying12.5ml glutamate with concentration of0.5%for3h) the content of GABA in mulberry tea dry matter reached3.322mg/g, which was the highest. According to the optimum preparation high GABA tea color yellow, green, open soup company’s assessment of rinsing, elegant taste, but there are certain bean smell, analysis the testing its main function ingredient polyphenols and flavonoids have these mulberry tea flavor quality ingredients. |
