Studies On The Nutritional And Functional Compounds Of Quinoa Tea And Its Antioxidant Activity

Quinoa(Chenopodium quinoa Willd.),a dicotyledon belonging to Amaranthaceae family,is originally from the Andean region in South America.Because of its excellent nutritional characteristics,the United Nations FAO recommend quinoa as the optimal?Whole Food?for human.Not only quinoa grain,the quinoa leaves also has high nutritional value.It is known that extracts of quinoa leaves have considerably positive effects on antioxidant,anti-cancer and other functions.However,at present,little information is available concerning quinoa leaves at domestic and foreign leading to their lower utilization.It is generally used in salad and bread as assistant ingredients.In this study,by using traditional processing techniques of tea,the fresh leaves and top shoots of quinoa sprouts at the growth period of 48 day were used to process to quinoa tea(black and green tea).The main nutritional and functional components were evaluated as well as the antioxidant activity.Meanwhile the saponin monomer compounds and volatile substances were identified and analyzed by mass spectrometry.The functional properties and flavor quality of quinoa tea were studied.These studies may provide useful information for the effective utilization of quinoa tea as functional food for promoting health.This study is mainly as follows:1.By traditional processing techniques of tea,fresh quinoa leaves and buds were processed into 4different types of quinoa tea:leaves green tea,bud green tea,leaves black tea and bud black tea,respectively.The analysis of major nutrient in quinoa tea showed that:the quinoa tea contained a high amount of total protein(37.54-41.32%),and bud tea was significantly higher than that of leaves tea(p<0.05);accordingly,the water-soluble protein content of bud tea was also significantly higher than that of leaves tea(p<0.05).The highest content of water-soluble protein was 84.91 mg/g in bud black tea.The content of free amino acids in black tea(40.31 mg/g of bud black tea and 38.24 mg/g of leaves black tea)was significantly higher than that of green tea(26.59 mg/g of bud green tea,23.64 mg/g of leaves green tea)(p<0.05).The soluble polysaccharide content of bud green tea was the highest,which was 24.24mg/g,while the lowest content of soluble polysaccharide was found in leaves black tea(12.82 mg/g).The fat content of quinoa tea varied from 2.63 to 3.86%.The moisture content of black tea is significantly higher than that of green tea(p<0.05),it could be because of a lot of water loss in the de-enzyming process during processing green tea.2.The analysis of functional compounds in the 4 different types of quinoa tea showed that:there were no significant differences among the content of total polyphenols(6.50-6.72 mg/g).The content of total flavonoids and total saponins is 3.93-4.45,7.09-10.22 mg/g,respectively.Moreover,the total saponins content of quinoa green tea was significantly higher than that of black tea;conversely,the gamma-aminobutyric acid content of quinoa black tea(leaves black tea 580.91?g/g;bud black tea555.38?g/g)was significantly higher than that of green tea(leaves green tea,472.13?g/g;bud green tea 326.72?g/g)(p<0.05).The antioxidant activity of water extract of quinoa tea was examined using three antioxidant assays in vitro(FRAP,DPPH,ABTS).The antioxidant activity increased linearly with the increasing of concentration of water extract of quinoa tea(R~2>0.98).3.The individual saponins of four quinoa teas were identified by liquid chromatography–mass spectrometry(LC-MS)techniques.Nine compounds were tentatively identified.Among them,5 and 6compounds were found in leaves green tea and bud green tea,respectively.While 3 compounds were found in leaves black tea and bud black tea.The types and contents of these compounds were different in the quinoa tea.So we hypothesized that the processing techniques may effect the conversion of saponin compounds.Further studies are needed to prove this hypothesis.The specific conversion mechanism needs further study.4.The volatile compounds of quinoa tea were identified by gas chromatography-mass spectrometry(GC-MS).A total of 36 volatile compounds were identified.A total of 24,26,21,20 compounds were identified in quinoa leaves green tea,bud green tea,leaves black tea and bud black tea,respectively.The volatile compounds of quinoa tea are mainly alkanes and olefins,and include aldehydes,ketones,alcohols,acids,and esters as well.