Abstract
This study aims to investigate the effects of raw materials and drying methods on the phytochemical and antioxidant capacities of instant sweet tea powder. Four raw materials of sweet tea leave powders (STUT) were extracted and dried with two methods (freeze-drying and spray-drying). The antioxidant capacity, total phenolic content (TPC), total flavonoid content (TFC), and phlorizin and trilobatin contents of obtained instant sweet tea powders were compared. In addition, the single-factor experiments coupled with response surface methodology were used to study the influences of solvent-to-sample ratio, extraction temperature, extraction time, and their interactions on instant sweet tea yield. Results showed that the optimal conditions for extraction were the solvent-to-sample ratio of 19:1 mL/g, extraction temperature of 88 °C, and extraction time of 30 min. The TPC, TFC, antioxidant capacities, and phloridzin and trilobatin contents of instant sweet teas were higher than those of STUT, and the TPC and TFC of freeze-dried instant sweet teas were higher than those of spray-dried instant sweet teas. Significant correlations were found among TPC, TFC, and antioxidant capacities (p < 0.01). The freeze-dried instant sweet tea produced by young leaves (prepared by oven-drying) showed the highest TPC, TFC, and antioxidant capacities, compared with other raw materials and drying methods.
Highlights
Lithocarpus litseifolius [Hance] Chun, popularly called “sweet tea”, is a herbal plant with an evident sweet taste that has been accepted as a daily beverage in the south of China for more than 1000 years, and was approved as a new food material in China in 2017 [1,2]
Extraction condition studies have been reported by many researchers, the evaluation of the instant tea powders of Lithocarpus litseifolius [Hance] Chun is very limited
The yield of the instant sweet tea powder increased with the extraction temperature from 55 to 85 ◦C, and this result was similar to other studies [14,24], suggesting that a higher yield of instant tea powder might be associated with a higher phenolic content
Summary
Lithocarpus litseifolius [Hance] Chun, popularly called “sweet tea”, is a herbal plant with an evident sweet taste that has been accepted as a daily beverage in the south of China for more than 1000 years, and was approved as a new food material in China in 2017 [1,2]. Many health benefits have been reported of sweet tea, such as antioxidant, antihypertensive, antihyperlipidemic, antihyperglycemic, anti-inflammatory, antimicrobial, and anticancer effects [1,5]. Instant tea powder is a kind of soluble solid tea produced by extracting tea leaves and drying the tea infusion. Instant teas produced from green, black, and dark teas have been studied by many researchers, while seldom studies have reported the instant sweet teas. Previous studies demonstrated that sweet tea and its dihydrochalcones showed antioxidant activity [7]. Whether these processes during instant sweet tea production can affect the phytochemicals and antioxidant capacity of sweet tea products is still unclear
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