Comparison of Different Flavour Components of Teas Found in the Major Stores Australia - Literature review Example

COMPARISON OF DIFFERENT FLAVOUR COMPONENTS OF TEAS FOUND IN THE MAJOR STORES AUSTRALIA. Introduction Tea is an evergreen perennial crop that grows naturally up to a height of 15 meters in the wild. When it is cultivated, it is maintained at low levels of 60-100 centimeters through cyclic pruning. Young shoots comprising of two leaves and a bud, a small proportion of the tea plant, is always harvested at regular intervals. The shoots are used for processing tea for export and local consumption. Processed tea can either be green or black tea. These two differ from the way they are processed. During processing of green tea, it does not go through oxidation process. Green tea has less caffeine. It is also rich in antioxidants compared to the black tea. On the other hand, black tea goes through most of the oxidation process which is characterized by polyphenol oxidase. During fermentation, which is the oxidative process, the leaves darken and change from green to red and finally to black. The flavor in tea is contributed by the presence of flavanol compounds that are oxidized during processing. Other flavors in tea can be added during the processing process or can be added through blending of the processed tea with different products. Most of the tea consumed in Australia is imported from India, China and Sri Lanka. However, Australia produces about 2000 tonnes of tea per year. This is less than 0.1 % of the total production of tea worldwide. In the recent past, Australia was ranked as a heavy consumer of tea, with every Australian consuming a total of 3.8kilograms of tea per year. Today with the coffee culture gaining popularity in Australia, the consumption of tea has declined to 0.8kilograms per year. High performance liquid chromatography (HPLC) coupled with Ultra violet (UV) detection system can be used effectively for the determination of the different flavor components in different tea products. Scientific importance of tea Tea is one of the most widely consumed soft beverages in the world. It plays a significant role to the economy of all the tea-producing countries, where tea is the leading foreign exchange earner and export commodity. Processed tea is rich in composition of phenolic substances. These phenolic substances are increasingly being used in production of other products apart from food and drinks. Phenolic substances in tea have been used in the production of environmentally friendly industrial products such as cleaning agents, and deodorizers. Antimicrobial agents have been formulated using tea. Lately, the demand for green tea has increased, due to human health concerns and preference. Studies have showed that regular consumption of tea can keep the body healthy and also it helps in boosting the immune system of the body. Young tea leaves contain polysaccharides, flavonoids, vitamins B, C and E, R-amino butyric acid, catechins compounds and fluoride which have prophylactic activities. The phenolic compounds in tea help fight chronic diseases such as cancer and cardiovascular diseases. Current tea breeding aims at coming up with tea clones with highly functional components such as catechins and flavanols. Biochemical composition of tea plant can be used as markers, to elucidate diversity of the tea clones. Catechins, which are part of the phenolic compounds found in tea, have been used as biochemical markers in diversity studies of tea. The number, diversity and the relative amounts of catechins in a tea plant have been used as biochemical markers to indicate the diversity in the tea clones. Tea contains sequences in its genome that can be used in the molecular studies and in the development of markers. These sequences in the genome of tea are highly polymorphic and are distinct. They can be used in development of markers such as Inter Sequence Random Repeats that can be used in the study of the diversity of other plants that are closely related to tea, since tea is highly outcrossing. Literature review. Botany of tea The tea plant belongs to the genus Camellia. This genus contains 12 sub genetic sections, one of which (Thea) contains species of cultivated tea. Owing to heterogeneity and many overlapping morphological, biological, biochemical and physiological attributes, the taxonomy of tea is perceived to be very complex. This has been complexed by the free hybridization amid species of the genus, leading to the formation of many inter-specific hybrids. Thus, genetic relationships, taxonomy and discovery of many new species have remained contentious. At the species level, a number of intergrades resulting from unlimited inter-crossing between dissimilar parents have been documented, but these have not been assigned the status of divide species. However, three discrete tea varieties namely the China variety (Camellia sinensis var sinensis(L), the assam variety; Camellia sinensis var Assamica and the southern form known as the Cambod race which have been recognized based on leaf features such as size, pose and growth habits have been identified. The three main taxa can also be differentiated by foliar, floral and growth feature and also by the level of their biochemical affinities. China variety is a dwarf and slow growing shrub, while the Cambod variety is an intermediate between the main taxa, which has now been confirmed by molecular marker studies. Owing to the out breeding character of tea and the resultant heterogeneity, most cultivars demonstrate a cline extending from extreme China- like plants to those of Assam origin. However, the numerous tea hybrids currently available are still referred to as Assam, Cambod or China varieties depending on their morphological proximity to the main taxa. Biochemical composition of tea A number of different chemical reactions initiated by an enzyme known as polyphenol oxidase during the fermentation process in tea are of realistic value in the production of manufactured tea for commercial purposes. Primary polyphenols in tea are readily oxidized during the fermentation process, transforming them to compounds with tanning properties. The oxidized polyphenols in black tea are responsible for the strength, briskness, colour, taste and the pungency of the black tea infusion. Polyphenols in tea remain intact in green tea as the steaming process immediately after plucking of the tea inactivates the enzyme polyphenol oxidase hence inactivation of the oxidation process. Natural polyphenols found in tea includes; epigallocatechin (EGC), epicatechin (EC), epigallocatechin gallate (EGCG), epicatechin gallate (ECG) and other compounds. The total green leaf catechin concentration as well as the ratio of dihydroxylated to trihydroxylated catechins can be used to elucidate genetic difference in tea clones. The pharmacological importance of these catechins decreases in the order of EGCG, EGC, ECG and EC. Other minor catechins present in tea includes, gallocatechin (GC), gallocatechin gallate (GCG), catechin gallate (CG) and catechin (C) which are also present in tea. Tea contains 30 to 42% polyphenols on the base of dry weight and a cup of green tea contains about 300 to 400 milligrams of polyphenols. The facilitation of public awareness of the health giving properties of tea has increased in the recent past. The majority of beneficial effects of tea have been accredited to primary polyphenolic constituents of green tea. Strong antioxidant potential of these polyphenols is thought to mediate most of the beneficial effects of tea. The health benefits in cancer, arthritis and cardiovascular diseases. Tea and health Tea is progressively being recognized as a healthy drink with most of the research on it focusing on its pharmacological properties and on the possible components that make it biologically active. Current tea breeding targets the selection of populations with high functional components such as catechins, flavanols, theanine, b-carotene, 2-amino-5(N-ethylcarboxyamido)-pentanoic acid, and polysaccharides. These biochemical’s have prophylactic activities that help in combating chronic diseases like cancer and other cardiovascular diseases. They are linked to lower heart disease and cancer risks through the action of flavonoids. Catechin compounds have been of focus for an anticancer. Biochemical’s in tea also relieve allergy symptoms and are shown to improve the body’s immunity. Studies have shown that catechins in tea inhibit diabetes including hyperglycaemia by reducing elevated sorbitol decreasing protein glycosylation and lipid peroxidation and also through inhibiting diabetic cataracts. Catechin compounds have been proven to have a variety of physiological functions, such as those enacting in the duodenum, colon, skin, lung, breast, oesophageal, pancreatic and prostate cancer function. In addition to prophylactic activity, catechins have been found to inhibit the growth of food borne pathogenic bacteria, and do not have adverse effects on the beneficial bacteria. Regular tea drinkers have been found to have healthier intestinal bacterial flora than those that drink less or no tea. In addition to the catechins, tea also contains caffeine which is found in young tea leaves. Caffeine in tea has prophylactic properties. Caffeine acts as a stimulant to the central nervous system (CNS) and cardiovascular systems. Different tea varieties and tea products harbor varying level of caffeine depending on the environmental and processing factors. Different tea products sold in Australian market There are many different tea products that are sold in the Australian market or stores. Most of these products are imported from the major tea growing countries. These products includes; iced tea, herbal tea, lemon tea, instant tea, ginger tea, flavoured tea, Assam tea, black tea, Darjeeling tea, purple tea, marsala tea and different tea bags. Herbal tea comprises of cool herbal tea and the pure herbal tea. Cool herbal tea is manufactures from freshly selected herbal leaves which are processed. These teas have prophylactic properties. Pure herbal teas which are also known as tea sans are pure blends of herbs without tea leaves these blends are made according to the choice and the requirement from the client. These pure herbal teas include; bone health tea, cooling tea, and blood cleansing tea. Instant teas are manufactured from high quality Assam tea. The instant teas have a minimum wastage and are known to be more convenient to use. Darjling tea is highly appraised by the domestic and the international market because of its unique flavour and also its well known refreshing fragrance. Cardamom tea has a fresh breath when consumed and its vital ingredients are made from a blend of cardamom powder whose vital ingredients are required to revitalise the body. The lemon tea is accredited for its good flavour and it’s also assumed to be rich in vitamins as it has been taken from the citrus plant. Lemon tea is form of cold tea which are prepared from top quality tea blended with lemon. Lime tea is prepared through blending of fresh tea with lime extracts. Lime tea is natural, fresh, rejuvenating and relishing. The healing properties of this tea are effective against common cold and can cure body aches as well as fatigue. Iced tea is the served chilled. All these types of tea have different flavors depending on the blend or the flavor desired by the consumer. Selection of analytical technique: The method selected for comparison of different flavor components in tea is through the use of robust High Performance Liquid Chromatography (HPLC). This method is effective for high- throughput screening and quantification of the different catechins and polyphenols in tea. Different peaks generated by the HPLC machine will account for the individual compounds in the tea. This method can be coupled with Ultra Violet (UV) detection of the percentage difference of polyphenols in different varieties of tea products. The data generated can be statistically analyzed through the analysis of variance (ANOVA) using MSTAT-C computer software. Relevance to the scientific or technical issue Tea is the second most popular beverage in the world after water. The health benefits associated with the consumption of tea are primarily attributed to the level of its catechin constituents. Tea is a complex matrix and all its components are can be analyzed by the use of a HPLC machine. This makes this method more convenient as all the components in tea can be quantified by the use of a single machine Strengths and weaknesses of the HPLC method of quantification and analysis. The major advantage of the use of a high performance liquid chromatography is that it can be able to quantify different flavor compounds in tea. The HPLC machine has an excellent resolution. It is highly reproducible and can be used to analyse many samples at ago. The peaks generated can be used to determine the difference in the flavour compounds in tea. presence of an acid in the mobile phase seems essential for complete and efficient resolution of catechins, specifically for elimination of peak tailing and its detection at shorter wavelengths. HPLC machine can be adapted for the analysis of other components in other different food stuffs. This method can also be adapted for studies on the effect of catechins intake on human health. The major drawback of conventional HPLC analysis of tea catechins is the compromise between speed and resolution resulting in typical analysis times of over 20 minutes or even longer. Complementarity of the HPLC machine in analysis of the various components. Ultra high performance of liquid chromatography enables faster separations and higher resolution which results in a higher resolution through the use of sub- 2 µm diameter particles. The presence of a thermo scientific HPLC system offers the flexibility of performance of the HPLC separations into a single platform. The presence of a quaternary pump delivers accurate and precise flows and the gradients over a wide range of flow rates within the column with a pressure of 1-1250 bar, to accelerate method development and to minimize the method flexibility. The thermo scientific perfluorophenyl columns enhance the retention and selectivity for the HPLC columns which enhances the separation of the different substituent aromatic compounds. The use of the micro millimeter particle column facilitates the rapid analysis of complex mixtures of samples. Compared to larger 5 and 3.5μm, sub-2 μm particles are less affected by flow rate, therefore faster flow rates within the pressure limits of the machine. This may be used to increase the throughput without detrimental effects on the peak efficiency of the column. Increasing the flow rates of the column decreases the analytical run time from 7 minutes to 3 minutes. When the flow rates are high the back pressures are also high, this makes it ideal for high throughput analysis. In this case some degradation in the resolution of the column is observed. This lowers the flow rate and the separation of the samples can be selected for the robust quantification. The mobile phase composition has a significant effect on the analyte retention and the quality of separations. The influence of the methanol and acetonitrile mobile phases in the HPLC greatly influences the performance of the analytical technique. Baseline resolution as well as excellent peaks can be achieved with a water/ methanol mobile phase. A water/ acetonitrile mobile phase can result in asymmetric peakshapes for some compounds. Water/ methanol base is clearly superior mobile phase for this type of separation (separation of different flavor compounds in tea). It has a higher viscosity compared to the water acetonitrile mixture which results in significantly higher back pressure which is an important consideration when this analysis is concerned. Increasing the column length increases the number of plates and it enhances resolution. Unfortunately, increasing the column length increases analysis times and the column back pressures. Long columns in length can be used with highly viscous water/ methanol mobile phases without exceeding the upper pressure limits of the pump. A 10 cm –long column can be chosen for this application as it provides both the necessary separation speed and resolution required for high throughput screening and quantitative analysis of the different components in a variety of tea. The data generated by the HPLC machine is highly reproducible. Through the analysis of the replication injection time of each analyte the effectiveness of the HPLC machine can be recommended. The retention time for each analyte was recommendable in the past related studies, while the peak area is the best. This indicates that it is an excellent method for the production of reproducible results particularly with the use of HPLC pump. The optimal wavelength for quantification of polyphenols is 275nm. This was determined based on the best signal to noise ratio for all analytes, and not on the most intense wavelength this ensures the lowest limits of detection and the limits of quantification. HPLC quantification method exhibit excellent reproducibility, with the peaks areas within the required range for analysis. Excellent linearity in detection response can be observed over three orders with a correlation coefficient greater than 0.99 for all the analyses. The use of HPLC machine to detect and analyze showed a high throughput. The machine leaves overlaid pressure traces of the samples demonstrating the exceptional stability of the HPLC pump. The machine has the ability to detect all the various components of the various teas. References Wang, H., and Helliwell, K., (2001). Determination of flavonols in green tea and black tea leaves and green tea infusions by high-performance liquid chromatography. Food Res. Int., 34, 223–227. Wang, H.F.; Provan, G. J.; Helliwell, K. (2003). HPLC determination of catechins in tea leaves and tea extracts using relative response factors. Food Chemistry. 81 : 307 – 312. Owuor, P.O. and Obanda, M. (2007). The use of green tea (Camellia Sinensis) leaf flavan-3-ol Composition in predicting plain black tea quality potential. Food Chemistry. 100: 873-884. ISO TC 34/SC 8/WG, (2003).Tea: methods for determination of substances characteristic of green and black tea. Determination of total polyphenols in tea: colorimetric method using Folin-Ciocalteu reagent. ISO 14502-2-2005E, (2005). Determination of substances characteristic of green and black tea. Contents of catechins in green tea: method using high-performance liquid chromatography. Goodarznia, G. and Abdollahi, A. (2009). Superheated Water Extraction of Catechins from Green Tea Leaves: Modelling and Simulation. Chemistry and Chemical Engineering.Vol. 16, No. 2, pp. 99-107. Hara,Y.(2001). Green tea. Health Benefits and applications. Marcel Dekker. Ny. Hara, Y (2006). Prophylactic functions of tea catechins. In Jain, W.K., Siddiqi, M.A. and Weisburger, J.H.(Eds), Protective effects of Tea on human Health. CAB International. Pages 16-24. Read More