| Rosemary officinalis is an evergreen shrub originated from Europe and the Mediterranean coast.It is a woody spice tree rich in essential oil and natural antioxidants.Rosemary leaves are loved by people because of their various aromatic values,and can be widely used in food additives,spices,cosmetics,medicine and other industries.At present,the main research and development and application products are rosemary extract,rosemary lotion,rosemary cosmetics and other products,and there is a lack of systematic research on the preparation process of rosemary tea products and the physicochemical properties of flavor substances.In this study,rosemary powder tea was prepared by high-temperature tea making technology.Simultaneous distillation extraction and gas chromatography-mass spectrometry(GC-MS)were used to analyze the aroma components of rosemary tea.Ultrasonic assisted extraction,tea brewing and liquid chromatography-quadrupole-high resolution tandem mass spectrometry were used to analyze the non-volatile components and taste components of rosemary tea Taking DPPH free radical,ABTS free radical,hydroxyl free radical scavenging ability and reducing ability of rosemary tea soup as indexes,the effects of stir frying process on antioxidant activity of rosemary tea soup in vitro were systematically analyzed.Combined with single factor and response surface methodology,the brewing conditions of rosemary tea were optimized,and the best stir frying process and brewing method were finally formed,so as to develop high-quality tea products for rosemary leaves And scientific brewing to provide theoretical basis and technical support.The main results are as follows:(1)Effects of frying technology on aroma components of rosemary powder tea.The aroma types of rosemary tea include alcohols,alkenes,ketones,esters,phenols,aromatic hydrocarbons,aldehydes,alkanes and others.With the increase of frying temperature,the contents of alcohols,ketones and esters all increased at first and then decreased,while the contents of olefins did not change obviously.The contents of aldehydes and alkanes decreased and gradually disappeared,while aromatic hydrocarbons were produced at higher temperature and showed an upward trend with the increase of temperature.The main aroma components of rosemary tea were 1-8 eucalyptol,verbenol,synthetic D-borneol,β-pinene,α-terpineol,geraniol,l-camphor,4-terpenol,myrcenol,geranyl acetate and camphene.With the increase of frying temperature,the content of 1-8 eucalyptol decreased first,then increased,and then decreased,while the content of camphene decreased and then increased,The content of other main aroma components showed the law of first rising and then falling.The results showed that the total content of main aroma components in rosemary tea increased first and then decreased.At 200℃ and 20 min,the total content reached the highest value of 85.26%.The above results showed that stir frying temperature could significantly affect the type and content of aroma components in rosemary tea.(2)Effects of frying technology on non-volatile components of rosemary powder tea.The main nonvolatile components of rosemary tea include terpenoids,flavonoids,organic acids,sugars,coumarins,amino acids and their derivatives.With the increase of frying temperature,the relative content of terpenoids did not change significantly,the content of flavonoids showed an upward trend,the content of organic acids and sugars showed a downward trend,the relative content of coumarins did not change significantly when the frying temperature was 150～250℃,but increased when the frying temperature reached 275℃,The content of amino acids and their derivatives did not change obviously.The main nonvolatile components of rosemary tea were salvianol,carnosic acid,luteolin,glucosylapigenin and oleanolic acid.The results showed that the relative content of salvianolic acid increased first and then decreased,the relative content of luteolin increased compared with the control sample before stir frying,the relative content of glucosylapigenin decreased,and the change of oleanolic acid was not obvious.When stir frying at 250℃ for 10 min,the relative content of luteolin increased,The total content of main nonvolatile components in rosemary tea was 21.75%.The results showed that stir frying temperature could significantly affect the types and contents of non-volatile components in rosemary tea.(3)Effects of stir frying technology on the taste of rosemary tea.The flavor substances of rosemary tea soup mainly include soluble sugar,flavonoids,alkaloids,amino acids,catechins,organic acids and other categories.The contents of rosemary tea water extract,catechins,soluble sugar,sweet amino acids and organic acids increased first and then decreased with the increase of frying temperature.The content of alkaloids had no obvious change,but the bitterness and freshness were not obvious.The content of amino acids decreased significantly,while the content of flavonoids increased on the whole.When the stir frying temperature was 250℃ and the stir frying time was 10 min,the content of rosemary tea water extract reached the highest of 19.68%.Stir frying temperature can significantly affect the type and content of rosemary tea flavor components.(4)Effects of stir frying technology on antioxidant activity of rosemary tea soup.The antioxidant experiment of rosemary tea showed that the scavenging capacity of DPPH,ABTS,hydroxyl radical and iron reducing capacity of rosemary tea were significantly improved after high temperature frying,and the scavenging capacity first increased and then decreased with the increase of frying temperature.When the frying temperature was 225℃ and the frying time was 10 min,the scavenging rate of DPPH free radical was the highest(76.60%);when the frying temperature was 250℃ and the frying time was 10 min,the scavenging rate of ABTS free radical was the highest(68.63%),the scavenging rate of hydroxyl free radical was the highest(75.71%),and the reducing ability of rosemary tea was the strongest,with the absorbance of 0.39.(5)The results of single factor experiment showed that increasing the brewing water temperature,prolonging the brewing time and reducing the brewing times would improve the ability of rosemary tea soup to scavenge DPPH,ABTS,hydroxyl free radicals and the reducing ability of tea soup.According to people’s daily life,pure water was the best choice for brewing water quality.The results of response surface optimization experiment showed that the best brewing conditions were brewing temperature of 90℃ and brewing time of 90℃ At this time,the antioxidant effect of rosemary tea was the best,and the DPPH free radical scavenging rate reached 93.15%.The results showed that the highest content of aroma components in rosemary powder tea was stir fried at 200℃ for 20 min,and the best flavor components and antioxidant effect of rosemary powder tea was stir fried at 250℃ for 10 min.The results showed that when the stir frying temperature was 250℃ and the stir frying time was 10 min,the flavor components and antioxidant properties of rosemary powder tea were better.The best brewing conditions of rosemary powder tea were brewing temperature 90℃,brewing time 30 min,once,and pure water. |
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