Sunday, October 30, 2011

The taste of milk tea

Boing Boing had a post which piqued my interest.

I think it's a matter of individual taste, some like their tea with a lot of milk, others only have a dash of it, with a stronger brew. Someone I know takes 5 spoons of sugar in his tea!  One of my research projects studies the interaction of milk with tea. The variation in taste may be due to the interaction between tea catechins and milk proteins.

Tea polyphenols, which include catechins found in the tea leaf, and their more complex derivatives formed during tea manufacture are responsible for the astringency (strong mouthfeel) of tea. These compounds bind to proteins on the tongue and lining the mouth —  that's how we experience the sensation of astringency. In a similar way, the catechins bind to the milk proteins and thereby reduce the astringency of the tea. People who don't like a 'strong' mouthfeel  will obviously prefer more milk in their tea. Interested readers should consult Tom Coultate's fine textbook  'Food: the Chemistry of its components'.

The full effect of milk proteins on tea is highly complex.  We understand the overall picture but the details are still the subject of active research by tea chemists, including myself. I hope to discuss this further in a future post.

Saturday, October 22, 2011

Tea — the Wonder Beverage. Part 1: The History of Tea

This is the first in a series of posts about my favourite beverage - Tea! A version of these posts appeared as a single article in "Chemistry in Sri Lanka",  May 2008 Vol.25 (2). 

Part 2 can be found here.

Part 1: The History of Tea

Tea is produced from the plant Camellia sinensis (L) O.Kuntze which belongs to the family Theacea. It is a native of South East Asian countries such as Tibet, Western China and Northern India. The three main varieties of tea are the China variety, Assam and the Cambodian variety. The tea plant is a small evergreen shrub; a vast number of hybrids have been developed to obtain optimum quality parameters such as flavour, strength, colour and also adaptability to specific agro-climatic factors.

Though Sri Lanka is world famous for tea, the beverage did not originate in Sri Lanka. It was the Chinese Emperor Shen Nung, many centuries ago, who first introduced tea as a beverage to his subjects as having a ‘fine flavour and a soothing sensation’. Ever since, the praises of tea have been sung by millions of others down the ages. The Chinese Historian Lu Yu wrote in his classic work on tea, that "It is better to drink such a beverage than wine, which loosens the tongue".

Tea plants of the Assam and Chinese varieties were introduced to Sri Lanka in the early 19th century when the country was a British crown colony known as Ceylon. Tea plants were grown in the estates near Kandy and in Nuwara Eliya but tea cultivation remained a minor activity at the time because coffee was the country’s main export crop. In the l870’s, however, a dreaded fungal disease known as the ‘coffee blight’ struck the coffee plantations. It destroyed the coffee plants and with them the entire coffee industry. The local economy then shifted to the ‘new crop’ — tea — within a few years.

The rapid substitution of tea for coffee was due to the initiative and untiring efforts of a Scotsman, James Taylor. In 1851 Taylor had signed on as an assistant supervisor on a coffee plantation in Ceylon. His employers, highly impressed with his work there, put him in charge of the Loolecondera estate to experiment with tea plants. The Peradeniya nursery supplied him with his first seeds around 1860. By l867, he had planted tea in several hectares of forest land which had been originally cleared for coffee plantation and demonstrated the feasibility of tea as a plantation crop. A few years later he set up the first tea ‘factory’ in Ceylon. In 1872, Taylor invented a machine for rolling the tea leaves, an important step in the process in which green leaves are converted to black tea. Ceylon Tea became famous in the tea trade and its success led to the opening of an auction market in Colombo in 1883, and formation of the tea dealer’s association some years later.

Today, there are many hybrids which have been developed for optimum quality and for adaptability to specific agro climatic conditions.  Tea is the most popular non-alcoholic beverage in many parts of the world. It is a valuable foreign exchange earning agricultural crop and is one of Sri Lanka’s major export commodities. The chemical composition, especially the polyphenolic compounds, of the fresh tea leaves are responsible for the unique qualities of tea giving it its distinct aroma, superior flavor and therapeutic properties, making it a wonder beverage indeed.

Tuesday, October 4, 2011

Food facts

Food facts - We often assume that bacteria and substances added to food cause problems in our food, but natural and environmental toxins are also responsible for adverse health effects.