Journal of Tea Science Research, 2024, Vol.14, No.1, 19-43 http://hortherbpublisher.com/index.php/jtsr 33 incorporated with WTE showed inhibition zones of 22 and 20 mm, respectively, against Pseudomonas aeruginosa, a foodborne pathogen (Stefanowska et al., 2023). 4.1.2 Antioxidant activity In the food industry, tea polyphenols as natural antioxidants have shown great potential in preventing food oxidation to inhibit undesirable changes in the physicochemical and sensory attributes, such as the formation of rancid flavors and discoloration (Gutiérrez-del-Río et al., 2021). Several mechanisms may be involved in the antioxidant activity of polyphenols, including radical scavenging, metal chelation, and enzyme regulatory activities (Yan et al., 2020). The antioxidant activity of white tea is frequently compared to other tea categories without common agreement, although the phenolic content has been found to be positively correlated with the antioxidant activity. Teas from the same cultivar but processed into different tea types, had an antioxidant profile that followed the order: green > white ≥ black tea, which was likely due to the higher degree of phenolic oxidation of white and black tea than the green tea (Carloni et al., 2013). However, in another study, the inherently higher polyphenols content of silver needle white tea led to its highest radical scavenging activity, followed by green and then black tea (Kaur et al., 2019). Another study demonstrated that green and white teas had similar but higher levels of total phenol and flavonoids than black tea, and thus better free radical scavenging activity (Pereira et al., 2014). The antioxidant efficacy of white tea varies according to the harvest season, extraction conditions, and storage time. Compared with summer and fall, white tea harvested in the spring season was reported to possess relatively higher amount of catechins, including EC, EGC, ECG and EGCG, corresponding to its highest antioxidant capacity (Ma et al., 2022). The extraction procedure of tea leaves would significantly affect the antioxidant activity of tea extract, as the chemical profile of WTE is largely dependent on the extraction conditions. Cold infusions of white tea (20 °C-25 °C, 2h) had a higher phenolic content 4.77-7.63 mmol/L gallic acid equivalents (GAE) compared to 1.43-4.02 mmol/L GAE in hot infusions (70 °C, 7 min) and the same trend was observed for the antioxidant activities (cold: 17.09-34.23; hot: 5.26-17.07 mmol/L trolox equivalents) (Damiani et al., 2014). Compared to the cold infusion prepared at room temperature (20 °C-25 °C) for a long time (2 h), the conversion of polyphenols to other compounds at the higher brewing temperature (70 °C) could be responsible for this phenomenon. Interestingly, under hot brewing conditions with a temperature range of 60 °C-98 °C and a time of 3-15 min, WTE prepared at 98 °C for 7 min had the highest phenolic content and antioxidant capacity (Pérez-Burillo et al., 2018). The storage time of white tea may affect the antioxidant efficacy of the derived WTE, as its chemical composition can change over time. Xu et al. (2019) found that for white tea aged 1, 3, and 5 years, longer storage time decreased the polyphenol content, which led to a decrease in the antioxidant activity of WTE against several free radicals. To achieve the best antioxidant capacity, it is critical to optimize the steps of converting white tea leaves into WTE in order to retain the maximum amount of tea polyphenols. The antioxidant activities of white tea can effectively preserve the oxidative stability of foods and act as a bioactive ingredient for the development of novel functional foods. After 7 days of refrigerated storage of ground beef, white tea powder (1%) effectively inhibited the formation of TBARS (secondary metabolites of lipid oxidation) formation by 89% compared with the untreated control (Kırmızıkaya et al., 2021). An active edible furcellaran/whey protein film with WTE was developed and effectively prolonged the shelf life of fresh soft rennet curd cheese (Pluta-Kubica et al., 2020). The WTE-containing film exhibited strong antioxidant activity and the sensory quality of cheese was rated the best at the end of a three-week storage period. In addition to food preservation, WTE is also formulated into functional foods to provide in vivo antioxidant activity, offer potential health benefits, and meet customer demand for naturally derived ingredients. 4.2 Therapeutic activities A myriad of studies on the therapeutic applications of WTE are found in the scientific literature (Table 6). The health benefits of white tea have been correlated with its bioactive compounds such as L-theanine, gamma-aminobutyric acid (GABA), and polyphenols (Bag et al., 2022).
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