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3 X‐Ray Fluorescence Studies of Tea and Coffee
Anatoly G. Revenko and Darya S. Sharykina
Institute of the Earth's Crust, SB RAS, Irkutsk, Russian Federation
3.1 Introduction
The histories of medicine and food are inextricably linked. For a long of time, nutrition was the only medicine for humans. At the present time, the results of food analysis are the main sources of information about their respective quality. The authors of the review Smichowski and Longonio [1] believe that all product components should be declared in the label; even those concentrations that do not pose a risk to human health or that do not pose a risk of exceeding permissible levels of toxic metals. Several countries have established databases of many product components. This information is used in the interests of the scientific community to support industry and government in the areas related to food and health.
Reviews of the current state of the problem of the application of X‐ray fluorescence analysis (XRF) in biology [2–4] and, in particular, in the study of the chemical composition of food products [3–7], showed that XRF can be successfully used to study such problems. The assortment of food products analyzed using XRF is very diverse: milk and dairy products, grain and bakery products, vegetables and fruits, spices, meat, fish and seafood, sugar, honey, alcoholic (alcohol, vodka, cognac, rum, wine, beer) and soft drinks (drinking and mineral water, juice, lemonade and cola, tea, and coffee). When examining food quality, they usually evaluate calorie content of carbohydrates, fats, fatty acids, sugar, cholesterol, proteins, carotene, vitamins, folic acid, as well as the content of individual elements Ca, Na, Fe, Mg, K, Zn, Cu, P, Se, etc. Consumed products are ranked by importance, depending on a few factors [8–10]. Several reviews discussed the use of XRF for studying the chemical composition of food products. Peculiarities of total reflection X‐ray fluorescence (TXRF) applications for wine and coffee research are considered in [11], food in [12, 13], natural waters in [14], tea and coffee in [15], drinks with sucrose matrix in [16]. Pashkova et al. [17, 18] presented reviews of the features of XRF application in determining elements in milk and dairy products. The climatic conditions for growing coffee beans, tea, fruits, and cereal products (wheat, rice, corn, etc.) are related to the expected quality and brand of the product. Measurement of trace elements is an effective way to verify the authenticity of product labeling [11–13,19–26]. It is a common practice to apply more than one classification method for solving this problem [25–28].
There are a few reasons to study the chemical composition of food products:
Study of biological processes occurring in plants during different periods of vegetation,
Evaluation of the influence of natural factors on the accumulation of individual chemical elements by plants,
Evaluation of food quality,
Product brand verification,
Checking of toxic elements content,
Evaluation of changes in quality products during long‐term storage.
It is obvious that XRF can make a significant contribution to the study of problems related to food and the health of the population. Unfortunately, information about XRF applications for these tasks is scattered in a large number of periodicals. Thus, publications from more than 35 journals were examined during the preparation of this chapter alone. Less than half of all articles on the application of XRF to investigate the chemical composition of tea and coffee were published in four journals. This is “X‐ray Spectrometry” (14), “Analytics and Control” (9), “Food Chemistry” (7), and “Journal of Analytical Atomic Spectrometry” (4). This chapter provides an overview of the current state of the problems troubling the use of XRF in the study of chemical composition of tea and coffee.
Tea is one of the most popular beverages on Earth. Annual tea production exceeds 3.5 million tons. Tea destroys intestinal infections and is a good antibacterial and antimicrobial agent. The complex chemical composition of tea depends on many factors, including soil