White tea, a minimally processed tea originated in China, has long been treasured for both its delicate flavor and its rich antioxidant properties. A recent study, led by Xu Ping of the Department of Tea Science at Zhejiang University, has cast a spotlight on how the potential health benefits of white tea, particularly its antioxidant properties and ability to inhibit enzymes linked to type 2 diabetes, may be diminished over time due to prolonged storage.
The research article, published in Food Science and Nutrition in February 2019, produced a fascinating comparison between white tea that has been stored for varying durations: 1 year (WT-1), 3 years (WT-3), and 5 years (WT-5). The study’s core findings suggest that as white tea ages, its antioxidant activity appears to wane, along with its ability to obstruct the enzymes alpha-amylase and alpha-glucosidase, vital players in the body’s carbohydrate digestion process. These enzymes are considered targets for the management of blood sugar levels in patients with type 2 diabetes.
DOI: 10.1002/fsn3.899
Keywords
1. White tea aging
2. Antioxidant activity
3. Enzyme inhibition
4. Diabetes management
5. Tea storage duration
Over the years, the tea industry and academic researchers have had a keen interest in understanding the health benefits of tea, with much attention given to green and black teas. However, white tea, often dubbed as the least processed tea with a high antioxidant count, is now at the center of scientific investigations aimed at unraveling its health-promoting potential. One particular aspect that has piqued the interest of researchers is how aging affects the quality of white tea—both in terms of its taste and its medicinal properties. The study conducted by Xu Ping and peers brings forth important insights into the progressive changes that occur in white tea during prolonged storage.
The Study’s Design and Findings
White tea samples stored for 1, 3, and 5 years were analyzed for their content of polyphenols—these compounds are the main bioactive components that possess antioxidant properties in tea. Polyphenols are believed to combat oxidative stress in the body, which is a contributor to various chronic diseases, including type II diabetes, cardiovascular diseases, and certain types of cancer. The team used established assays such as DPPH, ABTS, and FRAP to measure the tea’s antioxidant activities. In addition, in-vitro methods were employed to evaluate the tea’s inhibitory effects on two digestive enzymes linked to diabetes, alpha-amylase, and alpha-glucosidase.
The study found that antioxidant activities did indeed decline as the storage time increased. While all three white tea samples exhibited potent antioxidant activities, the decline was notably significant in WT-5. Similarly, the inhibitory effects on the enzymes alpha-amylase and alpha-glucosidase mirrored this trend, decreasing as the storage time lengthened.
The team also reported a reduction in the polyphenol content with the extension of storage duration. The implication of this finding can be far-reaching; the polyphenols in white tea are not only responsible for its health qualities but also contribute largely to its aroma, flavor, and overall sensory appeal. The reduction of polyphenols over time, therefore, affects both the health benefits and the quality that consumers can expect from aged white tea.
Impact on Health Benefits
White tea’s renowned health benefits are largely ascribed to its rich concentration of antioxidants. By scavenging free radicals, antioxidants protect the body’s cells from damage. Therefore, a decrease in antioxidant activity suggests that older white tea may be less effective in providing such protections when compared to freshly processed batches.
Moreover, white tea’s inhibitory effects on alpha-amylase and alpha-glucosidase hold implications for managing postprandial blood glucose—blood sugar levels after eating. By naturally slowing down the carbohydrate breakdown, these enzymes can help prevent the sharp spikes in blood sugar which are particularly problematic in individuals with diabetes.
The decrease in this inhibitory ability over time raises questions concerning the optimal storage conditions for white tea and perhaps the ideal shelf life for maintaining its health-promoting properties. This study underscores the importance of continued research to determine the mechanistic basis of aging-induced chemical changes in white tea.
Implications for Tea Production and Consumption
The findings of this study have significant consequences for tea producers, traders, and consumers alike. For producers and traders, understanding the age-related decline in key health compounds within white tea could inform harvesting, processing, and storage practices, impacting the commercial value of the product. Potential strategies might involve improved packaging solutions tailored to counteract the storage-time-related degradation of white tea compounds.
For consumers, particularly those focused on the health aspects of tea consumption, adjusting expectations or modulating consumption habits around the age of the white tea might become more prominent. There may be a growing demand for freshly harvested white tea or teas with guaranteed storage times to maximize their health benefits.
Recommendations and Conclusion
While this study brings new clarity to the field of tea science, it also highlights the need for further exploration. Future studies could focus on monitoring changes in white tea composition during storage under various conditions to optimize its long-term retention of health benefits.
Additionally, investigations into ways to preserve the polyphenol content and antioxidant activities in white tea over time could be beneficial. This may include examining natural and artificial preservatives or innovative processing and packaging techniques that limit oxidation processes.
Ultimately, the ideal storage time for maximizing the health benefits of white tea remains a new frontier waiting for discovery. Tea enthusiasts and health-conscious consumers alike can only hope for a future where enjoying a cup of white tea, regardless of its age, does not come with compromised benefits.
For now, what remains indisputable is that white tea is a beverage of great potential, not only within the confines of a traditional teacup but also as a significant contributor to the arsenal of natural compounds that support human health.
References
1. Xu Ping P., Chen Lin L., Wang Yuefei Y. “Effect of storage time on antioxidant activity and inhibition on α-Amylase and α-Glucosidase of white tea.” Food Sci Nutr. 2019 Feb;7(2):636-644. doi: 10.1002/fsn3.899.
2. Ademiluyi, A. O., & Oboh, G. (2013). “Soybean phenolic‐rich extracts inhibit key‐enzymes linked to type 2 diabetes (alpha‐amylase and alpha‐glucosidase) and hypertension (angiotensin I converting enzyme) in vitro.” Experimental and Toxicologic Pathology, 65, 305–309. doi: 10.1016/j.etp.2011.09.005.
3. Almajano, M. P., Carbó, R., Jiménez, J. A. L., & Gordon, M. H. (2008). “Antioxidant and antimicrobial activities of tea infusions.” Food Chemistry, 108, 55–63. doi: 10.1016/j.foodchem.2007.10.040.
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