How manufacturing processes affect the level of pesticide residues in tea

Hill Area Tea Science Division, Institute of Himalayan Bioresource Technology, Palampur-176061, Himachal Pradesh, India
Journal of the Science of Food and Agriculture (Impact Factor: 1.71). 12/2004; 84(15):2123 - 2127. DOI: 10.1002/jsfa.1774


Tea (both green and black) is consumed throughout the world, both for pleasure and therapeutic purposes. Most people will be unaware of their involuntary exposure to residues of pesticides lingering in processed tea and so possibly transferring into infusions of tea. The purpose of this work was to study the effect of green tea and orthodox black tea manufacturing processes on the fate of pesticides sprayed onto tea bushes (Camellia sinensis). The fates of residues of dimethoate, quinalphos, dicofol and deltamethrin in these two different types of tea manufacturing processes were compared. For black tea, the manufacturing process involves leaf harvesting, withering, rolling, fermentation and drying; and for green tea, leaf harvesting, microwave heating, rolling and drying. The two processes resulted in the same concentration factor of plant material into the dried commodity, while the decreases in residue levels were different for different pesticides. Initial microwave heating and dehydration in the green tea manufacturing process resulted in greater loss of pesticide residues than did withering and dehydration in black tea; no significant reduction in residue level resulted from the rolling and fermentation steps in black tea. Residue levels in both green and black teas were reduced during final drying. Copyright © 2004 Society of Chemical Industry

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Available from: Adarsh Shanker, Nov 19, 2015
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    • "As tea is subjected to infusion prior to consumption, residues of pesticides in tea and its transfer in brew must be monitored prior to permitting the consumption by human beings. A few reports are available on the degradation of certain commonly used pesticides and their residues in tea (Rajukkannu et al., 1981; Singh & Agnihotri, 1984; Manikandan et al., 2001, 2005 & 2006; Kumar et al., 2004; Sood et al., 2004; Tewary et al., 2005; Seenivasan and Muraleedharan, 2009). However, there is n o published information on the residues of bifenthrin in black tea, under the climatic conditions of south India. "

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    • "Zongmao and Haibin (1988) reported a 30–60% reduction in pesticide residues during the drying stage of tea manufacturing. Sood et al. (2004) found that initial microwave heating and dehydration during green tea manufacturing results in greater losses of dimethoate, quinalphos, dicofol and deltamethrin residues than withering and dehydration of black tea. Residues are substantially reduced both in green and black teas during the final drying process. "
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    ABSTRACT: Consumers are very aware of contaminants that could pose potential health hazards. Most people drink tea as an infusion (adding hot water); however, in some countries, including India, China, and Egypt tea is drunk as a decoction (tea and water are boiled together). An infusion usually brings the soluble ingredients into solution; whereas a decoction brings all soluble and non-soluble constituents together. Therefore, a cup of tea may contain various kinds of contaminants. In this review, we focus on green and black tea, because they are most commonly consumed. Our target was to examine the transfer rate of contaminants (pesticides, environmental pollutants, mycotoxins, microorganisms, toxic heavy metals, radioactive isotopes (radionuclides), and plant growth regulators) from tea to infusion/brewing, factors contributing to the transfer potential and contaminants degradation, and residues in or on the spent leaves. We concluded that most contaminants leaching into tea infusion are not detected or are detected at a level lower than the regulatory limits.However, the traditional practice of over-boiling tea leaves should be discouraged, as there may be a chance for more transfer of contaminants from the tea to the brew.
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    • "Dimethoate degradation was widely studied in some vegetable and cotton (Belal and Gomaa, 1979), some fruits and vegetable dips (Noble, 1985) and on guava (Khan et al., 2009). A few reports were available on the degradation of certain commonly used pesticides and their residues in tea (Rajukkannu et al., 1981; Singh and Agnihotri, 1984; Kumar et al., 2004; Sood et al., 2004; Manikandan et al., 2006; Seenivasan and Muraleedharan, 2009). However, there were no data available for the dissipation of dimethoate residues in black tea under south Indian climatic conditions. "
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    ABSTRACT: In order to investigate the dissipation pattern of dimethoate residues in black tea and its transfer into the tea brew, a field trial was conducted during dry weather at two locations of tea growing areas in Tamilnadu (India). Residues were quantified at different harvest intervals of '0' (3hrs after spray), 1st, 3rd, 5th, 7th, 10th and 14th day after the foliar application of dimethoate. A simple sensitive in-house gas-liquid chromatographic method for the determination of dimethoate residue in both black tea and tea brew were developed. The method was validated with accepted recovery of 83-104% and 77-85% from black tea and tea brew respectively at the minimum quantification limit of 0.03µg/g and adopted. The proposed method is based on the liquid-liquid extraction followed by gas chromatographic determination, using nitrogen phosphorus detector (GC-NPD) for quantification of dimethoate. Half-life value and pre-harvest interval (PHI) of the insecticide in tea were also arrived. The study indicated that the residue of dimethoate reached below the European Union Maximum Residue Level (EU-MRL) of 0.05µg/g on the 15 th day after spraying. Study reveals that about 70% of residue transferred to tea brew.
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