Black tea is the most highly fermented, and popular one, where the enzymatic oxidation of tea polyphenols leads to the formation of chemical compounds which are responsible for the characteristic, aroma, and colour. There are many forms of black tea found in the markets, namely stick-shaped, granular, and black tea bags which enclosed in small porous pocket and reinforced with epichlorohydrin (ECH) for wet resistance, usually used for a single serving. The UK Tea and Infusions Association (2017) reported that the use of teabags in the UK has increased from 5% in 1960 to 96% in 2007 and nowadays about 73% of the population use tea bags over loose tea making the number of tea bags used per day ~14.6 billion.

Harmful of Epichlorohydrin

Epichlorohydrin (ECH), or 1-chloro-2,3-epoxypropane is used as wet-strengthening agent in the production of cellulose products, such as tea bag paper to keep the tea bags from falling apart during the preparation of tea infusions. Therefore, tea infusions may contain ECH and/ or its metabolite 3-chloro-1,2-propanediol (3-MCPD). ECH is absorbed following oral administration and distributed within 2–4 h in different organs, while its metabolites are much more persistent and tend to accumulate during chronic exposures. Although ECH is an FDA-approved chemical, it is classified as a group 2A, a probable carcinogen and is proven to be harmful to human health.

Effect of Preparation Conditions on the Release of ECH

Effect of sucrose

The effect of adding sucrose on the release of ECH either from bagged or loose black teas was carried out by adding 3 or 6 g of sucrose to a beaker containing 100 mL of boiling deionized water and either one tea bag or 3 g of loose tea from each brand. The resulting infusion was stirred with a glass rod for about 1 min to ensure proper wetting and dissolving sucrose, steeped for 2 min, filtered through Whatman filter paper No. 42 and then extracted to determine the levels of ECH. Results showed non- significant differences between the using of 3 or 6 g of sucrose on the levels of epichlorohydrin in tea infusions either of tea bags or loose tea were recorded. 

Effect of pre-washing of tea bags

Tea bags were pre-washed by immersing in 100 mL of deionized water for 1 min and then stirred with a glass rod. The washed tea bags were put in a beaker containing 100 mL of boiling deionized water, stirred with a glass rod for about 1 min to ensure proper wetting, and then steeped for 2 min. The steeped infusion was filtered through Whatman filter paper No. 42 and then extracted to determine the levels of epichlorohydrin.

It was found that when tea bags were washed first with deionized water for 1 min and then the tea bags steeped for 2 min. Significant differences between washed and non-washed tea bags with water regarding the levels of epichlorohydrin. As it was expected from the high-water solubility of ECH which equals 65.90 g/L at 25 °C (NCBI 2022), ECH was significantly removed by water by 93, 93, and 94% for A, B, and C brands, respectively.

Reference

[1] Suheir M. F. Nour. (2022). Estimated daily intake of epichlorohydrin and certain heavy metals of bagged and loose black teas. Journal of Food Science and Technology, 60 2, 666–678