Standards of Tea
Tea is generally assessed for its quality by professional tea tasters. The tasters base their judgment on their previous experience of tea from the producing area and their knowledge of regional conditions and preferences. However, need for chemical analysis also arises when there is a suspicion that the product has been adulterated or it shows certain characteristics that are not normal to tea. Therefore, chemical quality parameters which reflect the intrinsic properties of the product are necessary for the industry.
Indian Standard for Tea to provide the needed guidelines, the Bureau of Indian Standards published IS 3633 ‘Specification for tea’ in 1966, based on extensive analytical data on teas grown and produced in different zones of the country. The requirements specified in original version of this standard did not apply to teas grown in Kangra Valley, Dehra Dun and Nilgiris as adequate data were not available on these teas at that time. Consequently, a number of tea samples were obtained from these regions and analyzed. On the basis of this data, in the second revision published in 1972 it was concluded that Dehra Dun and Nilgiri teas did not require a separate specification. However, at the same time it was recommended to the Government of India that it should explore the possibility of permitting some relaxation in these standards for Himachal Pradesh (including Kangra Valley teas). On the basis of scrutiny of extensive data, this standard was made applicable to both black and green teas. This aspect was highlighted in the second revision published in 1972.
In the preparation of this standard, due consideration has been given to the Prevention of Food Adulteration Act, 1954 and the Rules framed there under and Standards of Weights and Measures (Packaged Commodities) Rules, 1977. The standards, however is, subject to the restrictions imposed under these, wherever applicable. This Indian Standard states that tea shall be clean, free from extraneous matter and added colours and flavours and the tea shall produce a liquor of characteristic flavor.
To provide a yardstick for the assessment of quality of tea through chemical parameters minimum requirements for water extract, water-soluble ash, alkalinity of water soluble ash have been prescribed. To prevent adulteration, maximum limits for total ash and crude fiber have been stipulated. These requirements are aligned with ISO 3720 ‘Black tea – specification’ for all characteristics except water soluble ash and its alkalinity, which are presently under consideration for harmonization in Indian Standard, as third revision, as well as under PFA.
Besides, additional requirements for ECO Marking of the product have also been prescribed in the standard based on the Gazette Notification No.678 dated 30 August 1994 published by the Ministry of Environment and Forests. These include environmental consent clearances from the State Pollution Control Boards. Besides, stringent limits for contaminants namely, lead and iron fillings, have also been specified. In addition, ECO marked products are required to be packed in recyclable, reusable or biodegradable materials.
To ensure that the results of analysis are repeatable and reproducible, test methods should be standardized. International methods, if followed, provide the assurance that the methods have been validated after sufficient trials and are, therefore, reliable. The ISO standards on test methods for tea as well as instant tea have been adopted as Indian Standards under dual numbering system. In the third revision to the Indian Standard for tea, which is presently in the draft stage, all cross references for test method for determination of chemical characteristics have been made to Indian Standards harmonized with corresponding ISO standards, thus harmonizing the test procedures.
It is an important aspect of quality control, which provides confidence that a representative sample of the total production has been inspected against the safety and quality parameters. Tea is traded in different quantities and containers. To ensure that a sample is representative of the consignment, the number of containers to be sampled and procedure of random sampling has to be given. Procedure for taking primary samples and preparing bulk and laboratory sample conforming with international practices is prescribed in IS 3611:2000, Which is harmonized with corresponding ISO standard, under dual numbering. Instant tea in solid form is generally packed and transported in bulk in sealed bags of moisture-resistant material (that is, an immediate container), protected by an outer container. Owing to the hygroscopic nature and friability of the product, special precautions need to be taken in order to ensure that the drawing of samples does not adversely affect the sample itself or the remainder of the lot. Sampling procedures for instant tea in solid form harmonized with ISO 7516 have also been adopted as IS 13861.