Does green tea go bad?
In this brief guide, we are going to answer the question “does green tea go bad” with an in-depth analysis of the lifespan of green tea. Moreover, we are going to discuss the proper way to store green tea and the factors that affect the freshness of the tea leaves.
Matcha is considered a special sort of powdered green tea produced in Japan. After the Second World War, the rapid westernization of the Japanese lifestyle and diet led to a further fall in the consumption of matcha. Consequently, by 2016, ceremonial-grade matcha accounted for only 3.3% of green tea production in Japan (1).
So without much ado, let’s dive in and figure out more about it.
Does green tea go bad?
Yes, green tea does go bad after a certain time and as compared to other types of tea the shelf life of green tea is the shortest as it is an unfermented tea as in the world of teas the rule is “The more fermented the tea is, the longer will it last”. Almost all the green tea varieties are unroasted therefore they are the most volatile ones and have the shortest shelf life among all other types of teas.
Green teas contain higher content of catechins [(−)-epigallocatechin gallate, (−)-epigallocatechin, (−)-epicatechin gallate, and (−)-epicatechin] than both Oolong, pu-erh and black teas because fermentation process during the tea manufacturing reduced the levels of catechins significantly (2). For this reason, the chemical compounds in green tea are more susceptible to oxidation. This oxidation occurred during the production process, in the case of black tea. It was reported that tea catechins are not stable during long-term storage. During 6 months’ storage of green tea bags in their original containers at room temperature in the dark, the average content of EGCG decreased by one-third and ECG decreased by half (3).
It is recommended to use the green tea within 6 months after it is purchased to enjoy its premium fresh flavors as it is the peak quality time of the green tea. Nevertheless, green tea can last for about 1 year if it is kept properly in an air-tight container in a cool, dry, and dark place. However, there will be losses of antioxidants and aroma.
But when it comes to matcha, which is a powdered green tea variant it is recommended to use it within 1-2 months of opening. According to studies, the catechin degradation correlated with increasing aw and Tg , i.e. water mobility. Storage at aw 0.75 had the highest impact on catechins stability; the amount of catechins decreased by 39% after the food powder was stored at this condition for 45 days (4).
How to properly store the green tea?
The proper way to store green tea is to keep it in an air-tight container, jar, or air-tight bag in a cool, dry, and dark place. It should be noted that the place should not be humid or else the humidity of the environment can decrease the shelf life of the green tea (3).
When green tea is exposed to the moisture there are great chances of mold formation on it and it will go bad afterward. Moreover, it should also be stored away from direct sunlight. So a cool, dark corner of your pantry will be a good place to store your green tea.
You should always seal the pouch after scooping out the green tea. Moreover, you should never use a wet spoon to scoop out the tea from the package or the container in which it is stored.
You can read more about how to store tea leaves here.
What are the factors that affect the freshness of the tea leaves?
The factors that determine how long the tea leaves will stay fresh include the level of dryness, processing, oxidation, and roasting.
Level of dryness
The shelf life of the tea leaves directly depends upon the extent to which they are dried. If the tea leaves are dried thoroughly then the tea will have a considerably longer shelf life. On the other hand, if the tea leaves are not dried thoroughly then they will have moisture in them because of which they will lose their flavor and aroma quickly and will have a short shelf life. Drying is done to stop the fermentation and to reach the favorable moisture content to suppress microorganism growth (3).
Moreover, if the leaves are kept in a humid environment, then the moisture in the environment will result in mold growth on the leaves. The leaves that have mold growing on it will go bad quickly.
The more processed the tea leaves are, the easier will it be to dry them thoroughly and the longer will be their shelf life. That means that the shelf life of the black tea is more than that of the green tea as the former is a more processed one.
During green tea processing, the enzymes which catalyze oxidation are deactivated by heat treatment (pan-roasting or steaming), so that more tea catechins are retained. Processing of green tea leaves involving roasting, rolling and drying steps reduce catechins of the tea and stabilize the product, extending its shelf life. In the final product, total catechins are significantly reduced by up to 87% (4).
Oxidation is the process that brings out various flavors in the tea and also plays an important role to stabilize the otherwise volatile flavors and constituents of life. Some of the tea like oolong tea and green tea are the ones that are partially oxidized.
Roasting further helps in drying the tea leaves thoroughly, thus it helps to further stabilize the constituents of tea. Roasting also enhances the flavor profile of the tea. When it comes to roasting, every type of tea can be roasted but mainly the oolong tea is the one that is roasted most commonly.
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What can I do with expired tea leaves?
You can use the expired tea leaves as odor absorbers. You can keep them in your kitchen, fridge, or storage area so that they can absorb the strong odors there.
Moreover, you can also use them as fertilizers for your plants as the tea leaves still have some nutrients left in them. All you gotta do is to crush them and spread them in the soil surrounding your plant.
What happens if you consume expired green tea?
So when it comes to teas, the best before or the expiry time refers to the time after which the tea no longer has its great flavor and aroma. So as long as you are not that concerned about the flavor and aroma of the green tea, you can go for a green tea that is past its prime age, and even if you consume expired green tea, it won’t harm you.
However, tea can be contaminated with microorganisms, such as Aspergillus niger, during storage. The risk associated with tea bags is probably low, as the tea is usually prepared in the kitchen by the addition of boiling water, which likely kills the spores, although this has not been clearly demonstrated (5).
But if there is a mold in your green tea, it is recommended that you should not use it.
In this brief guide, we answered the question “does green tea go bad” with an in-depth analysis of the lifespan of green tea. Moreover, we discussed the proper way to store green tea and the factors that affect the freshness of the tea leaves.
- Sekine, Kae. The impact of geographical indications on the power relations between producers and agri-food corporations: A case of powdered green tea matcha in Japan. Geographical Indication and Global Agri-Food. Routledge, 2019. 54-69.
- Zuo, Yuegang, Hao Chen, and Yiwei Deng. Simultaneous determination of catechins, caffeine and gallic acids in green, Oolong, black and pu-erh teas using HPLC with a photodiode array detector. Talanta, 2002, 57, 307-316.
- Kosińska, Agnieszka, and Wilfried Andlauer. Antioxidant capacity of tea: effect of processing and storage. Processing and impact on antioxidants in beverages. Academic Press, 2014. 109-120.
- Ananingsih, Victoria K., Amber Sharma, and Weibiao Zhou. Green tea catechins during food processing and storage: A review on stability and detection. Food Res Int, 2013, 50, 469-479.
- Bouakline, Adel, et al. Fungal contamination of food in hematology units. J clin microbiol, 2000, 38, 4272-4273.