[Objective] We aimed to investigate the differences of polyphenols content in Anxi Tieguanyin tea among different seasons and relationship between polyphenols and tea quality.[Method] The content of total polyphenols ...[Objective] We aimed to investigate the differences of polyphenols content in Anxi Tieguanyin tea among different seasons and relationship between polyphenols and tea quality.[Method] The content of total polyphenols and main phenolic compounds was analyzed by spectrophotometry and HPLC and the sensory quality assessment was carried out.[Result] There were significant differences in the content of polyphenols in Anxi Tieguanyin tea among different seasons.The summer tea had a higher content of polyphenols and ester type catechins and a heavier undesirable taste with more bitterness and astringency than spring tea and autumn tea with lower quality in general.The flavonol content of spring and autumn tea was significantly higher and the color of tea soup was better.[Conclusion] This study provided a basis for the quality improvement of summer tea by regulating the content of total polyphenols and provided a basic data for chemical analysis of Oolong tea.展开更多
Although tea is grown in agro-ecological regions widely varying in environmental factors affecting yield and quality, planters usually import genetic materials across the different growing regions assuming genotypes w...Although tea is grown in agro-ecological regions widely varying in environmental factors affecting yield and quality, planters usually import genetic materials across the different growing regions assuming genotypes with good quality attributes in one location maintain their status in all regions. However, tea quality has not been replicated in new production regions. Black tea quality is influenced by the green leaf quality precursors including caffeine, total polyphenols and individual flavan-3-ols which are precursors of theaflavins and thearubigins, key plain black tea quality parameters. Factors influencing levels of the precursors compounds have not been quantified for popular Kenyan tea cultivars. The influence of geographical production location and seasons on levels and ratios of the quality precursors for 10 black tea popular clones grown in three locations in Kenya under uniform agronomic inputs were monitored. Caffeine varied significantly （P _〈 0.05） with clones and location but not with season. The flavan-3-ols and their ratios all varied （P 〈 0.05） with clones and site but not with season, with significant interactions （P 〈 0.05） between locations and clones, and locations and seasons. These results explain the observed variations in plain black tea quality due to clones and location of production. Thus, farmers in different locations are unlikely to produce black tea of same quality. It is therefore necessary to evaluate new tea genotypes in intended growing areas to establish cultivars suitable for producing high quality plain black teas in the locations. Seasonal variations in plain black tea in Kenya are unlikely to vary significantly due to flavan-3-ols.展开更多
Grapes are important sources of antioxidants compounds and one of the most used varieties to elaborate juices is ＂Isabel＂, or ＂Isabella＂, as it is called in North-America. This study aimed to evaluate the antioxid...Grapes are important sources of antioxidants compounds and one of the most used varieties to elaborate juices is ＂Isabel＂, or ＂Isabella＂, as it is called in North-America. This study aimed to evaluate the antioxidant activity of Isabella grape juices from the tropical semi-arid climate produced in Brazil on March and September, 2010. Total phenolics and anthocyanins were determined, as well as the antioxidant capacity by DPPH, FRAP and hydrophilic ORAC methods. Test T was used to compare statistical difference at 5% of significance level. As expected, the results showed that the season can play a significant role on phenolics content and antioxidant power. Polyphenols content in juices varied from 82.9 ± 0.92 to 102.2± 1.59 mg GAE 100 mL1- and anthocyanins content ranged from 44.3 ± 2.01 to 129.5 ± 2.82 mg cyanidin-3-glucoside 100 mL-1. Regression analyses showed a high correlation of antioxidant capacity and anthocyanins content. Grapes from Sao Francisco River Valley demonstrated to be a good source of antioxidant for human diet.展开更多
基金Supported by Program of Fujian Provincial Bureau of Quality and Technical Supervision--Applied Research about Exogenous Enzymes for Quality Improvement of Anxi Tieguanyin Tea(FJQI2009006)Program of Administration of Quality Supervision,Inspection and Quarantine--Application of Chemical Analysis and Quality Control in Traceable Identification of Anxi Tieguanyin Tea(201210075-3)~~
文摘[Objective] We aimed to investigate the differences of polyphenols content in Anxi Tieguanyin tea among different seasons and relationship between polyphenols and tea quality.[Method] The content of total polyphenols and main phenolic compounds was analyzed by spectrophotometry and HPLC and the sensory quality assessment was carried out.[Result] There were significant differences in the content of polyphenols in Anxi Tieguanyin tea among different seasons.The summer tea had a higher content of polyphenols and ester type catechins and a heavier undesirable taste with more bitterness and astringency than spring tea and autumn tea with lower quality in general.The flavonol content of spring and autumn tea was significantly higher and the color of tea soup was better.[Conclusion] This study provided a basis for the quality improvement of summer tea by regulating the content of total polyphenols and provided a basic data for chemical analysis of Oolong tea.
文摘Although tea is grown in agro-ecological regions widely varying in environmental factors affecting yield and quality, planters usually import genetic materials across the different growing regions assuming genotypes with good quality attributes in one location maintain their status in all regions. However, tea quality has not been replicated in new production regions. Black tea quality is influenced by the green leaf quality precursors including caffeine, total polyphenols and individual flavan-3-ols which are precursors of theaflavins and thearubigins, key plain black tea quality parameters. Factors influencing levels of the precursors compounds have not been quantified for popular Kenyan tea cultivars. The influence of geographical production location and seasons on levels and ratios of the quality precursors for 10 black tea popular clones grown in three locations in Kenya under uniform agronomic inputs were monitored. Caffeine varied significantly （P _〈 0.05） with clones and location but not with season. The flavan-3-ols and their ratios all varied （P 〈 0.05） with clones and site but not with season, with significant interactions （P 〈 0.05） between locations and clones, and locations and seasons. These results explain the observed variations in plain black tea quality due to clones and location of production. Thus, farmers in different locations are unlikely to produce black tea of same quality. It is therefore necessary to evaluate new tea genotypes in intended growing areas to establish cultivars suitable for producing high quality plain black teas in the locations. Seasonal variations in plain black tea in Kenya are unlikely to vary significantly due to flavan-3-ols.
文摘Grapes are important sources of antioxidants compounds and one of the most used varieties to elaborate juices is ＂Isabel＂, or ＂Isabella＂, as it is called in North-America. This study aimed to evaluate the antioxidant activity of Isabella grape juices from the tropical semi-arid climate produced in Brazil on March and September, 2010. Total phenolics and anthocyanins were determined, as well as the antioxidant capacity by DPPH, FRAP and hydrophilic ORAC methods. Test T was used to compare statistical difference at 5% of significance level. As expected, the results showed that the season can play a significant role on phenolics content and antioxidant power. Polyphenols content in juices varied from 82.9 ± 0.92 to 102.2± 1.59 mg GAE 100 mL1- and anthocyanins content ranged from 44.3 ± 2.01 to 129.5 ± 2.82 mg cyanidin-3-glucoside 100 mL-1. Regression analyses showed a high correlation of antioxidant capacity and anthocyanins content. Grapes from Sao Francisco River Valley demonstrated to be a good source of antioxidant for human diet.
