Welcome to the first Around the world in 80 particles blog of the new decade! I’m John, a recent addition to the team of Product Technical Specialists here at Malvern Panalytical.
The first months of the year always bring some chilly temperatures in the weather around here. In order to cope with that, it can sometimes help to take some time to sit down somewhere comfy and slowly enjoy a cup of a world favorite hot beverage: Tea!
Yes, tea is the name of the blog this time around, and you’re probably wondering how particle size contributes to the creation of your everyday brew.
The manufacture of tea follows several steps, including withering of the collected tea leaves, preconditioning, rolling, fermentation and finally drying. It is in the rolling stage where particle size comes into play. Withered tea leaves are passed through rollers and broken down into particles of different sizes. One method of rolling is the crush, tear, curl (CTC) process, which reduces the particle size even further, in the range of 1.7 mm to 250 micrometers1. The tea found in your average teabag is of course of this more broken, dust-like variety.
The dust particles are normally separated (graded) into their different size fractions using sieving. This is a very traditional technique that we regularly come across in the particle sizing field. Today, with the prominence of laser diffraction technology in particle size analysis, several organizations have chosen to use this in addition to or as an upgrade on sieving to assist in the quality control of their products.
The larger the size of the particles, or the closer to the original leaf the tea source is, the higher grade the tea generally is. However, tea dust doesn’t necessarily come with a reduction in quality, taste or price, especially if they have come from the leaves of more sophisticated teas! The smallest of these dust pieces of the leaf (size range of 250 – 500 µm) brew at a much faster rate compared to the whole leaves due to the increased total surface area, giving them an optimal use in tea bags. They also give brews a deeper color and increased strength (more caffeine), while retaining most of the flavor from the original leaves2.
So, the next time you’re browsing the tea aisle in your local supermarket, maybe trying to find the strongest, most flavorsome and fastest brewing tea on offer, you will be able to consider the (very) little things that go towards your perfect cup!
- C. Astill, M. R. Birch, C. Dacombe, P. G. Humphrey and P. T. Martin; J. Agric. Food Chem. 2001, 49, 11, 5340-5347