Assessing Caffeine Contents in Tea Infusions Decaffeinated by Hot

Nutrition and Food Sciences Research Vol 7, No 2, Apr-Jun 2020, pages: 37-46 Original Article Assessing Caffeine Contents in Tea Infusions Decaffeinated by Hot Water Treatment Using High Performance Liquid Chromatography and Studying the Effects of Mint Leaf Addition to Tea Infusions on Improvement of their Total Polyphenol Contents Tahere Razzaghi1, Maryam Salami2, Mahnaz Qomi3, Maryam Moslehishad4 1- Nutrition and Food Sciences Research Center, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran 2- Department of Food Science and Engineering, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran 3- Medicinal Chemistry Department, Pharmaceutical Sciences Research Center, Pharmaceutical Sciences Branch, Islamic Azad university, Tehran, Iran 4- Department of Food Science and Technology, Safadasht Branch, Islamic Azad University, Tehran, Iran Received: September 2019 Accepted: December 2019 A B S T R A C T Background and Objectives: Due to the health concerns of people about caffeine, several techniques have been developed to remove caffeine from tea; however, these techniques include limitations. The objective of the present study was to remove caffeine from dried tea leaves using hot water treatment. Materials and Methods: Hot water treatment was used to decaffeinate green and black tea leaves using two stages of brewing. Caffeine of the tea infusions was extracted using liquid–liquid extraction technique and quantified using high performance liquid chromatography. Furthermore, pH, total polyphenol content and antioxidant activity were assessed using electronic pH meter, Folin-Ciocalteu method and ABTS method, respectively. Sensory evaluation was carried out using 5-point hedonic scale test. Tea infusions were prepared within two stages of brewing at 1, 3 and 5 min as primary and 7 min as total brewing times. Results: After 3 min of primary brewing time, decaffeination rates of Ceylon black, China green and Iranian green teas were assessed as 47.7, 81.55 and 85.99%. Antioxidant activity of these samples included 87.7, 85.99 and 81.55%, while total polyphenol content included 83.03, 44.44 and 37.7%, respectively. In general, pH and total polyphenol content of decaffeinated tea-mint infusions increased significantly. Conclusions: Effects of brewing time on caffeine concentration of the tea infusions were revealed in this study. In conclusion, hot water treatment is a safe method and includes a high efficiency for the decaffeination of green and black teas. Keywords: Tea, Caffeine, Polyphenols, Mint Leaf, HPLC Downloaded from nfsr.sbmu.ac.ir at 5:00 +0330 on Sunday October 3rd 2021 [ DOI: 10.29252/nfsr.7.2.37 ] Introduction Tea (Camellia sinensis) is the most popular drink may include relatively adverse effects such as sleep after water. Due to beneficial health effects of tea, it is deprivation, abortion, miscarriage and consumed regularly for approximately 120 mL per hypersensitivity (5, 6). Furthermore, this may cause day (1). Tea is a rich dietary source of polyphenols. health problems in psychiatric patients and other One of the most important polyphenols in tea is sensitive groups such as reproductive aged women catechin. Up to one-third of the tea dry weight and children (3). Proportion of the caffeine extracted includes catechin and other phenolic compounds such from tea leaves to infusions varies from 51.5 to 85.2% as quercetin, myricetin and kaempferol with high and tea can be considered one of the major sources of antioxidant capacities (2). Tea polyphenols include a caffeine for heavy tea drinkers (7). Due to the health variety of effects on consumer health, including concerns of people for caffeine, numerous techniques antioxidant, anticancer, antiaging and antiviral effects. have been developed to remove alkaloids such as The moderate caffeine intake is not possibly harmful caffeine from teas, including use of organic solvents for a majority of the healthy adults (3, 4). However, (8, 9), activated carbon (10), supercritical CO2 regular consumption of excessive amounts of caffeine extraction (11, 12), microwave enhanced ice water *Address for correspondence: Maryam Salami, Assistant professor, Department of Food Science and Engineering, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran. E-mail address: [email protected] Tahere Razzaghi, et al: Antioxidant and total polyphenol contents of decaffeinated tea enriched with mint extraction under vacuum (5), lignocellulose column pH of decaffeinated infusions and their TPC was (13), poly(acrylamide-co-ethylene glycol another aim of this study. dimethylacrylate) as adsorbent (14), microbial or Materials and Methods enzymatic system (15) and high-pressure processing (16). Although these methods can remove caffeine Materials from teas, they include limitations such as risk of Folin-Ciocalteu reagent (FCR), chloroform, solvent residue (15, 17), expensive equipment (17), potassium persulfate, sodium carbonate, disodium long production time or difficult scaling up for hydrogen phosphate, sodium dihydrogen phosphate industrial production (9). In fact, one of the safest and solvents of the highest purity for HPLC analysis methods for removing caffeine from teas is hot water were purchased from Merck, Germany. The ABTS treatment (17). reagent was purchased from Sigma (St. Louis, MO, Effective factors on tea infusion compositions such USA). Deionized water used in the experiments was as caffeine, total polyphenol content (TPC) and produced using water deionizer (Younglin Ultra 370 antioxidant activity include grade (particle size) of the Series, South Korea). China green tea (CGT), Iranian tea leaves (18) and various parts of the tea plant (19). green tea (IGT), Ceylon black tea (CBT), Iranian Moreover, preparation parameters, including black tea (IBT) and mint leaves were purchased from quantities of tea and water (18), infusion time (1, 19), local tea shops in Tehran, Iran. Standard solutions of and water temperature, have been shown as major ascorbic acid, caffeine and gallic acid (purity ≥ 99%) used as standards were purchased from Merck, factors of tea preparation (18). Since pH of the black -1 tea is low, tea is considered an acidic drink. A variety Germany. A stock solution (600 mg L ) of ascorbic of health problems can occur for the body in acidic acid was prepared by dissolving ascorbic acid in states. Acidic diets cause diseases such as dental deionized water. Other concentrations (800, 1300 and 1500 mg L-1) were prepared by diluting stock solution erosions (20), metabolic bone diseases, calcium -1 nephrolithiasis, chronic diseases (21) and risk of with deionized water. A stock solution (20 mg L ) of overdiagnosing gastroesophageal reflux diseases (22). caffeine was prepared by dissolving caffeine in deionized water. Other concentrations (40, 100, 200 Mint (Mentha longifolia) is well known for its -1 antioxidant properties. Recent research has shown and 500 mg L ) were prepared by diluting stock that mint is a rich source of polyphenols. Polyphenols solution with deionized water. A stock solution of in mint are phenolic acids such as rosmarinic acid, gallic acid (0.001 mM) was prepared by dissolving caffeic acid and ferulic acid with significant health gallic acid in deionized water. Other concentrations effects such as antiallergenic, anti-inflammatory, (0.002, 0.003 and 0.004 mM) were prepared by antimicrobial and antioxidant properties (23). diluting stock solution with deionized water. However, pH of mint is relatively high (20). Preparation of tea infusion samples Mint herbal tea is used as a hot beverage that is To decrease caffeine content of the tea infusions, naturally caffeine free (24). Nowadays, consumption tea samples were brewed within two stages. In all of functional food is increasing. Food and food stages of tea preparation, water volume and Downloaded from nfsr.sbmu.ac.ir at 5:00 +0330 on Sunday October 3rd 2021 [ DOI: 10.29252/nfsr.7.2.37 ] ingredients with potentially positive effects on health temperature included 100 (mL) and 98–100 (◦C), in comparison to basic nutritional benefits are called respectively. The ratio of tea leaves to water was functional foods (25). Due to the health benefits of tea constant but the brewing time of tea varied in each and mint, they can be classified as functional foods stage (Table 1). In Stage 1 (primary brewing stage), (26). Although use of decaffeinated teas is increasing, boiling deionized water (100 mL) was added to dry their safety concerns have not been dismissed. tea (2 g) using porcelain teapot. This was brewed on Therefore, development of safe, fast and economical steam water at various times (Table 1). Stage 1 was decaffeination methods is currently an important issue the caffeine extraction stage. In Stage 2 (secondary for the tea industries (17). The major aims of this brewing stage), tea infusion was filtered through filter study were extracting maximum quantities of caffeine papers and boiling deionized water (100 mL) was from dried leaves of green and black teas using hot added to the residues using porcelain teapot. This was water treatment as a safe method within two brewing brewed on steam water at various times. Then, stages. Assessing effects of mint leaf addition to the infusions were filtered through filter papers. Based on infusions in the second brewing stage on increasing internal standard methods (27), the optimal brewing tea time includes 6–7 min. 38 38 Nutrition and Food Sciences Research Vol 7, No 2, Apr-Jun 2020 Tahere

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