A Comparison of the Polyphenolic and Free Radical Scavenging Activity of Cold Brew versus Hot Brew Black Tea (Camellia Sinensis, Theaceae)

Chathuranga Manhari Magammana,Long Wang,Cheryl Rosita Rock,Virginia Gray

doi:10.5539/jfr.v8n3p35

Abstract

Recently, a new trend called cold brewing gained popularity in the tea and coffee beverage industry. Cold brew and hot brew black tea may have different sensory qualities and antioxidant levels because of their polyphenolic properties and brewing processes. The objectives of this study were to determine antioxidant properties and polyphenolic content of commercial brands of cold brew and hot brew black tea. The total phenolic content of the cold brew tea was determined to be 0.19 mg/mL gallic acid equivalents/100 g and hot brew tea was 0.43 mg/mL gallic acid equivalents/100 g when assayed by Folin-Ciocalteu&rsquo;s reagent method. The total flavonoid content of the cold brew tea was 0.40 mg/mL catechin equivalents/100 g and hot brew was 1.01 mg/mL catechin equivalents/100 g. Moreover, antioxidant capacity of cold brew and hot brew black tea was analyzed where their ability to scavenge DPPH radicals was 86.3% and 88.1% respectively. There was a significant difference in total phenolic content between hot brew and cold brew (p = 0.004). Similarly, there was a significant difference in total flavonoid between cold brew and hot brew (p = 0.004). Additionally, there was a significant difference in DPPH scavenging activity between cold brew and hot brew (p = 0.016). Overall, it can be concluded that although cold brew tea contained a lower amount of phenolics and flavonoids as compared to hot brew tea, they both were able to scavenge DPPH radicals in nearly same capacity.

Highlights

1.1 Consumption Trends and Tea TypesTeas are classified as the following: black, green, oolong and white tea, which are generally processed using the standard steps: withering, rolling, fermentation and drying with slight variations based on the type (Shinde, Das, & Datta, 2013)
The total phenolic content was lower in cold brew black tea (0.19 mg/mL gallic acid equivalents (GAE)/100 g or 43.7 mg/230 mL GAE/100 g and mean absorbance value was 0.78 ± 0.04) than hot brew black tea (0.43 mg/mL GAE/100 g or 98.9 mg/230 mL GAE/100 g and mean absorbance value was 1.74 ±0.10; Table 1)
The results showed that there was a significant difference in total flavonoid between cold brew and hot brew (p = 0.004; Table 2)

Summary

Introduction

Teas are classified as the following: black, green, oolong and white tea, which are generally processed using the standard steps: withering, rolling, fermentation (oxidation) and drying (firing) with slight variations based on the type (Shinde, Das, & Datta, 2013). 1.2 Cold Brewing in Tea and Coffee Industry. A new process of cold brew has gained popularity in the beverage industry (Refermat, 2017). In the coffee industry, cold brew is drawing the attention of a new generation referred to as millennials (aged 18-34; Fry, 2016) in that many of them consider it as their drink of choice (Strand, 2017). New frequent innovations and products such as unique tea products similar to cold brew coffee continue to expand the beverage industry (Tea Association of the U.S.A. Inc., 2017)

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Conclusion