Drinking Pu-erh tea is inherently an elegant pursuit that integrates the body and mind with nature, allowing one’s thoughts to return to the natural world. However, if “smoky” off-flavors appear during the tea-drinking process, the wonderful experience of tasting tea is instantly diminished.
These odors may be caused by improper processing or storage; in response, Professor Zhou Hongjie and his team from the Pu-erH Tea College of Yunnan Agricultural University have discovered a “secret weapon” that can effectively improve the quality of raw Pu-erh tea while reducing such risks.
This “secret weapon” is negative oxygen ions.
As an important component of reactive oxygen, the health benefits of negative oxygen ions in the air should not be underestimated; they are even referred to as “air vitamins.” In addition to functions such as sterilization, dust reduction, air purification, boosting immunity, and regulating human physiological functions, they can also improve the quality of raw Pu-erh tea.
This “secret weapon” was discovered through comparative experiments.
Using 100g tea samples each of the 2003 Longji Qingbing and 2005 Gudao Qingbing from the Pu-erh Tea College of Yunnan Agricultural University, they utilized the strong reducing properties of negative oxygen ions to keep the tea cakes in direct contact within a 30cm effective range under conditions of an initial temperature of 25°C and 60% humidity.
The test tea samples were stored in natural storage and negative oxygen ion storage environments for two months (the natural storage condition was an office with 40–50 negative oxygen ions/m³, while the negative oxygen ion storage condition was a forest with 10,000–20,000 ions/m³).
As a result, after storage in high concentrations of negative oxygen ions, the aroma of substances such as 1-hepten-3-ol, which represent characteristic floral and fruity notes, increased, while the aroma of (smoky) compounds represented by phenylethyl alcohol decreased.
In other words, the “smoky” off-flavors contained in linalool and its oxides were significantly reduced, and other burnt components and unpleasant, irritating odor components were even eliminated.
Based on the sensory quality assessment of shaiqing tea in GB/T 22111-2008 “Geographical Indication Products—Pu-erh Tea,” under the high-concentration negative oxygen ion storage condition of 10,000–20,000 ions/m³, the quality showed a bright light yellow liquor, mellow taste, reduced bitterness and astringency, lessened astringency, and increased sweetness and smoothness, with an aroma that facilitates the transformation of various aged fragrance substances.
The experimental results strongly confirm that under negative oxygen ion storage conditions, the beneficial aromatic components are enhanced and off-flavors such as “smoky” notes are eliminated, leading to an overall improvement in the quality of raw Pu-erh tea; this provides a favorable basis for future scientific storage.
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Author: Lam Sam (LamSam), the Old Tea Head
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