Development Of Healthy Instant Tea With Rich ?-Aminobutyric Acid (GABA) And Low Caffeine

With many functional components,tea shows some excellent physiological functions.Gamma-aminobutyric acid?GABA?is an important inhibitory neurotransmitter,which has functions of lowing blood pressure,anti-convulsion and anti-arrhythmia.However,because of low GABA content in tea,enrichment treatment is needed to reach the concentration for good health function.Caffeine,a stimulant of central nervous system,has some refreshing effect.For high concentration of caffeine in tea,excessive intake will stimulate central nervous and affect sleep.By now,traditional tea products keep a trend of convenience,quickness and economy.For the maximum maintenance of the original color,flavor and taste,instant tea is nutritious,hygienic and convenient,which is deeply loved by tea drinkers.Therefore,the development of instant tea products with high GABA and low caffeine shows a significant socio-economic value.This paper aims to optimize GABA enrichment process,caffeine removal technology with supercritical CO₂ extraction,and instant tea extraction process,as to develop tea products with high GABA and low caffeine,which provides more choices for the development of multifunctional tea beverage.The main results are as follows:?1?The optimization of GABA enrichment process was discussed.The results showed that the soaking of glutamic acid solution was in favor of GABA accumulation.The influences on GABA accumulation were different,more for glutamate concentration and less for temperature and pH,respectively.Different methods of alternate anaerobic treatments of tea leaves can significantly improve the level of GABA accumulation in fresh tea leaves.Orthogonal experimental results showed that with 1.5%of glutamic acid soaking?pH 6?by the way of 2 h soaking-1 h airing-2 h soaking-1 h airing-2 h soaking at 30?,GABA content was up to450.86 mg/kg with an enrichment ratio of⁹.?2?Supercritical CO₂ extraction technology was used to remove the caffeine in the tea.Single-factor experimental results showed that extraction temperature,extraction pressure,extraction time and water amount have a significant influence on the extraction efficiency of caffeine.The best conditions are as follows:40?,24 MPa,4 h and 40%water amount.The orthogonal experiments of four factors order were as follows:extraction pressure>extraction temperature>extraction time>water amount.In the optimal conditions?extraction temperature40?,extraction pressure 24 MPa,extraction time 4 h,water addition 40%?,the removal rate of caffeine reached 91.3%and GABA loss rate was 7.5%.?3?Solvent extraction process of tea was investigated.Single-factor experimental results showed that extraction temperature,extraction time,solid-liquid ratioand pH have a great influence on the extraction efficiency.The best conditions were as follows:70?,50 min,1:15g/mL and pH 5.Optimalextraction process of tea was explored by orthogonal experimental design.For GABA,pH and temperature showed the maximumand minimum influence on extraction efficiency,respectively.The influence of solid-liquid ratio and extraction time had similar influence.For Caffeine,the primary and secondary relationship was as follows:temperature>time>pH>solid-liquid ratio.The best operating conditions were chosen as:extraction temperature 70?,extraction time 65min,solid-liquid ratio of 1:10g/mL,pH 5.Under these conditions,the content of GABA and caffeine was 0.60%and 0.69%,respectively.With the combination of alternately glutamic acid soaking,supercritical CO₂ extraction and solvent extraction technology,GABA content in tea products increased significantly and caffeine content reduced obviously,which provided a technical foundation for the development of high value tea products.