Can You Brew Tea in the Refrigerator?

Just about every source regarding brewing tea in the refrigerator for iced tea presents it as an alternative to making sun tea. This makes sense as sun tea was an ill-informed fad that produces a bacterial soup. But the idea of using the sun and a glass container is to slowly brew the tea and thus end up with a better tasting, less bitter tea. Since making sun tea facilitates the growth of bacteria, maybe using the fridge to brew the tea even more slowly will be even better!

This is a lot to unpack for something as simple as iced tea, so I’ll try to make it as simple and direct as possible. I will not tell you about my grand and adventurous experiment where I made approximately 100 batches of tea. I’ll simply tell you whether or not you can make tea in the fridge and whether it is better or safer than sun tea.

Is It Possible To Brew Tea in the Refrigerator?
How Do You Brew Tea in the Fridge?
The Problem With Sun Tea
Is There Bacteria In Tea?
Why The Fridge is Only Marginally Safer
Less Bitter Tea is Not Objectively Better Tea
Cold Brew Tea Is Not Better Than Hot Brew Tea, Only Different

Is It Possible To Brew Tea in the Refrigerator?

You can certainly brew tea in the refrigerator. However, the assumption that it is rendered bacteria-free is an incorrect one.

Sun tea has gone bye-bye because the CDC and other experts informed the public it is unsafe, and various food-oriented websites moved over the refrigerator tea without asking if it is truly any safer.

When we boil water and then place tea bags (or loose tea) in it, we are killing the germs in the water but also killing the germs in the tea. Yes, your tea is not sterile. It harbors bacterial spores.

How Do You Brew Tea in the Fridge?

Its just as simple to brew tea in the refrigerator as it is to brew it using hot water. It simply takes longer.

Use one tea bag or one teaspoon of tea per 6 to 8 ounces of cold water. Place the water and tea together in a large glass container, preferably sealed or covered. Making sure the tea is submerged, let it brew in the fridge for 6 to 12 hours. If using green tea, some sources suggest a shorter brewing time of 6 to 8 hours.

If you are using loose leaf tea, the tea can be placed in a tea ball or tea bag. It is also possible to use a tea basket that will fit in the top of a small jar, and then seal the jar with plastic wrap or other covering.

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The Problem With Sun Tea

If you place tea bags in water and heat it in a glass container in the sun, the hottest it will get is around 130 F. This is not hot enough to kill the bacteria in the tea or the water. It is, in fact, just about right to encourage the bacteria to grow and grow. So, when you make sun tea, you are making a nice tepid bacteria soup.

While it does not seem that sun tea has been reported to make anyone sick, it should be patently obvious why you probably shouldn’t drink it.

Is There Bacteria in Tea?

Now let’s talk about the bacteria that may be present in your tea bags. Many different types of bacteria could be found in tea. One type of bacteria that has been found, in large numbers, in cultured tea leaves is coliform bacteria.

Coliform bacteria are organisms like Escherichia coli and members of the genus Aerobacter, found in the intestinal tract of humans and other animals. In other words, they are fecal bacteria. Tea can become contaminated during growing, harvesting, processing, transporting, or storage. You can also be responsible for contaminating tea during the brewing process.

People have become sick from drinking iced tea at restaurants that was contaminated with coliform bacteria. This contamination was likely introduced at the restaurants but it is possible for the bacteria to come from the tea itself. ¹

Why The Fridge is Only Marginally Safer

Since long warming in the sun isn’t enough to kill the bacteria in tea and in water, I don’t have to tell you that the fridge will also not kill the germs. E coli and other pathogens will grow more slowly in typical fridge temperatures, but they will grow. Since cold brewing of tea is only marginally safer than warm brewed tea or ‘sun tea’ in terms of the potential presence of viable pathogenic bacteria, the question is whether cold brew tea is better to drink.

Does cold brew tea taste better? Does it have fewer tannins? If it does, is this a good thing?

cup of Earl Grey tea with half of bergamot fruit

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Less Bitter Tea is Not Objectively Better Tea

While a less bitter tea may taste better to those who dislike the bitter flavors in tea, it is the bitter components, called polyphenols, that contribute much of the beneficial heatlh effects.

Tannins are often named as the undesirable bitter component of tea. Tannins are polyphenols. These go by different names in tea, such as catechins. One of the main catechins in tea is epigallocatechin gallate (EGCG), present in large amounts in green tea and one of the main reasons for its astringency and bitterness, but also for its beneficial effects on health.

Since it is possible to measure the amount of these polyphenols in tea through objective scientific analysis, rather than taste tests, we can ask whether there is scientific evidence that cold brew tea has fewer tannins and thus is less bitter.

Such evidence exists and while there are varying temperatures used in research, the evidence is unclear. Some research shows that there is less total antioxidant activity in teas brewed at colder temperatures while other research shows similar activity in both methods.

Were Tea Bags Created By Accident?

However, it does seem clear that as the temperature decreases, the amount of total phenolic and flavonoid compounds in the brewed tea tends to decrease. ¹

One experiment, a Ph.D. thesis entitled A Comparison of the Polyphenolic and Antioxidant Properties of Cold Brew versus Hot Brew Black Tea (Camellia Sinensis, Theaceae ) by Magammana, Chathuranga Manhari, evaluated cold brew and hot brew black tea to determine antioxidant properties and the polyphenolic content:

The total phenolics content of the cold brew tea was determined to be 0.19 mg/mL gallic acid equivalents/100 g and hot brew tea was 0.43 mg/mL gallic acid equivalents/100 g when assayed by Folin-Ciocalteu’s reagent method. The total flavonoid content of the cold brew tea was 0.40 mg/mL catechin equivalents/100 g and hot brew was 1.01 mg/mL catechin equivalents/100 g.

Moreover, the antioxidant capacity of cold brew and hot brew black tea were analyzed where their ability to scavenge DPPH radicals were 86.3% and 88.1% respectively. There was a significant difference in total phenolics content between cold brew and hot brew (p = 0.004). Similarly, there was a significant difference in total flavonoids between cold brew and hot brew (p = 0.004).

Additionally, there was a significant difference in DPPH scavenging activity between cold brew and hot brew (p = 0.016). Overall, it can be concluded that although cold brew tea contained a lower amount of phenolics and flavonoids as compared to hot brew tea, they both were able to scavenge DPPH radicals in nearly the same capacity. ²

This would seem to suggest that traditional brewing methods, using water at near-boiling temperature for a brew of around 3 to 5 minutes, result in a more healthful tea. However, similar antioxidant behavior was found in the teas brewed using both methods.

Brewing at cold temperatures, like those found in the refrigerator, may produce a less bitter tea but not necessarily a more healthful tea. Note that green teas have higher total antioxidant content than black teas, regardless of brewing method and at least one study found higher flavonoids in cold brew green tea.

It is also worth noting that ‘cold’ doesn’t always mean ‘refrigerator’ cold in research settings. For example, 30 C or 86 F may be considered cold when compared to 90 C or 194 F. However, brewing tea at 86 F is just as dangerous as brewing it in the sun.

Cold Brew Tea Is Not Better Than Hot Brew Tea, Only Different

It is up to you which you find more important and thus ‘better’ and it is not clear, even anecdotally, that cold brew tea is noticeably less bitter. If you are interested in the health benefits of tea, there is no convincing evidence that cold brewing is more healthy than traditional hot brew. Cold brew tea may taste less bitter but each method may have similar antioxidant behavior. However, cold brew tea may harbor potentially dangerous pathogenic bacteria, thus being less healthy.