The Hidden Role of Vitamin C in Bottled Tea and Its Impact on Flavor

Today, for many people, drinking tea means consuming bottled tea. In this article, we focus on the distinctive flavor characteristics of bottled tea.

Addition of Vitamin C as an Antioxidant

When you visit convenience stores, supermarkets, or drugstores, you will find various types of bottled tea products. Take a moment to check the ingredient labels on these products. With very few exceptions, most contain added vitamin C. According to manufacturer websites, the purpose of adding vitamin C is to "supplement the vitamin C lost during heating in bottled green tea." While this explanation is not incorrect, based on my experience in food product development at a food manufacturer, I believe the primary purpose of adding vitamin C is actually to prevent oxidation. Vitamin C, also known as ascorbic acid, is a powerful antioxidant. Even when bottled tea is filled with nitrogen gas, quality deterioration occurs over time, including browning of color and formation of bitterness due to polyphenol oxidation. Vitamin C, as an antioxidant, can dramatically slow the oxidation rate, making it essential for green tea beverages. In fact, when you observe products in stores, vitamin C is added not only to green tea but also to black tea, barley tea, oolong tea, and even milk tea. The following reference material contains measured vitamin C levels in commercial green tea beverages for those interested. https://hijiyama-u.repo.nii.ac.jp/record/80/files/16.pdf

How Vitamin C Addition Affects Tea Flavor

Setting aside the debate about whether adding vitamin C is good or bad, the key point is that the flavor of bottled tea that many people are accustomed to is actually tea flavor combined with the flavor of vitamin C. According to the reference material linked above, commercial bottled beverages contain on average 100 to 150 mg of vitamin C per 500 ml of water. Since 1 gram equals 1,000 mg, you might think 100 mg is a negligible amount. However, if you actually taste vitamin C, even a small amount is extremely sour. To test how much this amount of vitamin C affects flavor, I dissolved 100 mg of vitamin C in 500 ml of water. Interestingly, even this amount gave the water a slight sourness. It was subtle, but the presence of acidity was clearly recognizable. Conventionally cultivated green tea, which follows modern agricultural practices including fertilizer application, contains high levels of amino acids and low levels of polyphenols. This gives it a mellow flavor that is honestly quite different from bottled green tea. However, when vitamin C is added, the flavor changes to become refreshing and clear, similar to commercial bottled green tea. With the addition of vitamin C, a refreshing acidity remains in the mouth after drinking, making the tea flavor more clear and refreshing. In a sense, this is similar to lemon tea, and this characteristic makes it generally appealing. Manufacturers likely view the flavor change caused by vitamin C as a positive factor.

Natural Tea Grown Without Fertilizer Has a Clear Flavor

What is interesting is that tea produced without fertilizer or pesticides has a naturally very clear flavor. When the components of tea grown without fertilizer are quantitatively analyzed, polyphenol content is several times higher than in conventionally cultivated tea. I had believed that the clear flavor of tea grown without fertilizer was due to its high polyphenol concentration. However, it is possible that tea with high polyphenol content also contains high levels of vitamin C. In fact, when comparing sencha and gyokuro, sencha contains more polyphenols than gyokuro, and sencha also contains more than twice the vitamin C content of gyokuro. Of course, I have never conducted a comparative analysis of vitamin C between conventionally cultivated tea and natural tea grown without fertilizer, so this remains a hypothesis. This is a very interesting topic, and I would like to conduct quantitative analysis in the future if the opportunity arises. Below is reference material (a Japanese research paper) with analytical values for vitamin C (ascorbic acid) and polyphenols in various commercial green teas. While it does not account for differences in cultivation conditions or changes during processing, it may be useful for those interested. https://www.jstage.jst.go.jp/article/vso/19/0/19_KJ00002901055/_pdf https://web.archive.org/web/20150906062007id_/https://www.jstage.jst.go.jp/article/cha1953/1994/80/1994_80_23/_pdf