Tea is one of the most popular drinks in the world, and is consumed by almost two-thirds of the world’s population. It is not only one of the oldest-known beverages in the world but also an antioxidative agent available in everyday life, which can help to prevent a wide variety of diseases such as cancers and heart diseases (Luczaj and Skrzydlewska, 2005; Yang, 2002). Tea processing has undergone many incarnations in the past 100 years, from loose tea to blended, packet teas, tea bags and finally to instant teas, ready-to-drink teas and flavoured teas. As science and technology probe the chemical and metabolic processes triggered by the consumption of tea, tea has the potential to be the beverage of the 21st century (Boriah, 1997).
Instant tea, a product dried from tea infusion, was first produced, from black tea in England in 1940. Although its production has been researched for a long time, the production and acceptance of instant tea is a major problem facing the tea industry today (Wherkoven, 1974). In a country consuming the traditionally hot beverage, the instant product has not, so far, enjoyed the same acceptance as has instant coffee. Only in the last few years has there been any serious attempt to market instant tea in the United Kingdom outside the catering and vending sector. The market is still in an early stage of development with several freeze-dried products of reasonable quality consisting of 100 percent tea solids retailing alongside mixes containing whiteners or sugar and other flavouring (Hart, 2008).
The manufacturing process of instant tea is similar to that of instant coffee, that is, the preparation of an aqueous extract, followed by concentration and drying of the extract to yield a completely soluble powder or granules. In the case of tea, however, controlling the processing condition in order to avoid product degradation is more critical. The extract may be prepared from conventional black tea or from the undried green leaf, which may be partly processed before extraction. In either case, the extraction conditions must be precisely controlled in order to provide both satisfactory quality and a commercially viable yield. After extraction, the liquors require very careful handling to minimise undesirable changes before the final drying step, which may be through spray- or freeze-drying.
Soluble or instant tea has recently become very significant largely because of the success of instant coffee and the sale of beverages from vending machines. Instant tea is now used for iced drinks, which have greatly increased its demand. The growing popularity of instant tea takes place at the expense of leaf tea. Convenient products have the advantage of having little or no waste in the household (Lee, 1968). Improvements in terms of the product as well as its suitability for providing an attractive drink from vending machines are constantly under study.
There are several methods for the preparation of instant tea. The details of the techniques involved are mostly secret or protected by patents. Lipid/water-soluble tea polyphenols, which are natural antioxidant extracts, are also available in the market. Most of the existing methods for the production of instant tea use hot water extraction. Some of the methods commonly used are described below. Figure 1 shows the commercial production flow chart for instant/soluble tea powder. Hindustan Unilever Limited has developed and patented a process for preparing instant green tea by heating the fresh leaf to a temperature sufficient to inactivate the enzymes. Then, the leaf is comminuted, extracted with hot water and dried by conventional means like spray-drying or freeze-drying. In another method developed by the Tea Research Institute of Ceylon (Wickremasinghe, 1977) for the production of cold water soluble tea concentrates and powders, tea leaves are first extracted with hot water. Then, the extract is subjected to gel filtration to effect the separation of non-phenolic compounds like chlorophylls, proteins, polypeptides and polysaccharides, while retaining the polyphenolic compounds. The resultant filtrate is then concentrated to obtain a cold-water-soluble powder.
A process for the production of a soluble tea product with champagne-like properties capable of being reconstituted in hot, warm, or cold water has been developed and patented in the USA. In this method, a dilute tea extract obtained from the combination of Manchurian mushrooms, green or black tea leaves and sugar, is concentrated and reconstituted in water. The processing steps according to this invention are generally applicable to the preparation of both hot and cold-water-soluble tea beverages from any tea leaf.
Another method of manufacturing a black leaf tea that is infusible in hot or cold water was also developed and patented. The process involves macerating freshly-plucked tea leaves, allowing them to ferment, firing the leaves to arrest fermentation and then drying them to yield black leaf tea. The tea leaves are then treated with a solubilising compound, selected ascorbic acid, dehydroascorbic acid, 1-scorbamic acid, 5-phenyl-3,4-diketogamma-butyrolactone (4-phenyl-2,3-diketogamma-butyrolactone) or their salts and mixtures in an amount that is sufficient for the black leaf tea to be soluble in water at 5° to 100° C.
Instant tea powder
There are certain difficulties involved in producing instant tea to create a beverage comparable with ordinary tea infusion. The problems are connected with the liquoring characteristics, flavour or aroma and with the tea quality itself.
In the general method of extraction using boiling water, the flavour of this product is generally poor. When the hot infusion cools down, it becomes turbid and particles settle down after prolonged cooling. This is called tea cream, and de-creaming is thus necessary since cream affects the clarity and appearance of cold, water-soluble instant tea. This can either be made soluble by chemical and enzymatic means or discarded as a waste product by physical means during the manufacture of instant tea. In addition to the problems related to the quality of instant tea, which include a weak aroma, poor taste and insufficient cold-water solubility, low productivity is also one of the important problems (Pintaro, 1977). Moreover, when instant tea is made from prepared black tea, the process is highly expensive and energy intensive (Schott, 1988).
In view of these drawbacks, IIT Kharagpur has developed a novel technique for the production of instant tea from fresh tea shoots. In this method, a part of the juice is expressed from the fresh tea shoots and converted to soluble tea by freeze-drying. Then, the residual part is converted into ordinary tea granules by hot air drying. Thus, both consumable products can be obtained from the same leaf. As the method does not use any heat treatment for the expression of juice, the quality of the soluble tea is also maintained (Sinija et al, 2007).
Like its counterpart soluble coffee, soluble tea is at the crossroads. As a market category, it faces many challenges, but there are also many opportunities. Not only does soluble tea offer means of storing and transporting tea in a more compact and stable form, it also offers the consumer both ease of use and a fairly good bargain. As persuasive as those arguments are, both from the perspective of value and convenience, lifestyle patterns seem to augur well for soluble tea to grow as a convenience. As Starbucks has proven, consumers value the social interaction that they participate in while buying their drinks almost as much as the drink itself. Furthermore, many time-crunched consumers view even the act of boiling water as a lengthy indulgence that they cannot afford. Many drink tea at home in the morning or evening; however, there are opportunities for consumption growth during the middle of the day when hardly anyone is at home.
Like coffee, tea’s biggest enemy is not its usual sparring partner (coffee) but the vast world of soda pop and bottled, fruit-flavoured confections which, although often sweeter than soft drinks, are often perceived as a ‘healthy’ alternative. The capacity of soluble tea, as an ingredient, to participate in or even cross over into this world may well determine whether it will flourish or fade.
The recent reports on the healthfulness of tea have helped it become a fad. Therefore, it seems apparent that soluble tea will succeed as a flavouring in ready-to-drink products, either as the chief flavour component or in concert with others, and it will also probably be consumed outside the home during the day. As per the opinion of tea experts, it is up to the members of the tea industry to market their products aggressively in the manner in which new age beverage marketers promote their products and in the format that today’s consumers want. In their opinion, the traditional tea market is shrinking, and growth will be apparent in the speciality tea segment, which includes soluble teas and ready-to-drink teas. This is the only segment in which the market is growing steadily.
Green tea is considered a speciality because of its positive health effects. As green tea is rather bland in flavour, people are trying to mix in various fruit and herbal extracts to give it some uniqueness. The health benefits and innovative flavour of white tea also make it a future trendsetter.
Soluble tea has immense potential, as, when executed properly in a formula, it offers superior delivery of taste, astringency and colour. Unfortunately, somewhere along the line soluble teas earned a reputation of being ‘the powdered tea’. However, in reality, soluble teas are simply an aqueous extraction of the leaf, which is dried at very high temperatures. This drying process locks in the flavour and characteristics of the leaf and accomplishes several important goals: it ensures microbiological purity (as a result of the heat); the tea becomes an efficient and waste-free raw material; and it is an amazingly consistent product, which will not vary greatly across stocks.
In addition, it is a product that gives a fresh clean taste, and this is particularly important to the consumer. Therefore, quality tea extracts that are highly soluble and are completely clear are gaining more importance. Again, the soluble tea category does, in general, pose some fairly tough challenges. It will be perhaps easier to overcome these obstacles if the members of the tea industry choose to view (and market) tea as a new beverage rather than an ancient one entitled to a consumer following.
References
• Boriah, G (1997). Constraints to raising output. In The Hindu Survey of Indian agriculture’ (pp.
103-105). Chennai: Kasturi and Sons Ltd.
• Hart, A (2008) Hot Water Soluble Tea, http://teabeverage. blogspot.com, accessed on December 1, 2008.
• Hill, Julie B Anon, 2003. Soluble tea suffers an image problem. Tea International. Tea and Coffee Trade Journal, http://goliath.ecnext.com.
• Process of making a soluble tea product with champagne-like properties, US patent 5543165,
http://www.freepatentsonline.com/5543165.html.
• Luczaj, W and E Skrzydlewska, Antioxidative properties of black tea review article, Preventive
Medicine 40 (2005) (6), 910-918.
• Pintauro, 1977 Pintaro, N (1977). Tea and soluble tea products manufacture. Food Technology
Review, 38.
• Sinija, VR, Mishra, HN and Bal, S (2007) Process Technology for Production of Soluble Tea Powder. Journal of Food Engineering, 82(3): 276-283.
• Wherkoven, J (1974). Tea processing. FAO Agricultural Bulletin No. 26. FAO and The United Nations, Rome.
• Wickremasinghe, RL (1977). Process of making cold water soluble tea concentrates and powders
(patented work). Tea Research Institute of Ceylon, Sri Lanka.
• Yang, 2002 CS Yang, Effects of tea consumption on nutrition and health, Journal of Nutrition 132 (2002) (Suppl. 12), 2409-2412.
The authors are from the Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur |
