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Coffee
How long does cold brew last?
Whether you’re looking for a less acidic brew or an extra kick of caffeine, there’s no question that cold brew’s versatility appeals to a wide range of consumers. In fact, brewing in cold water instead of hot has a profound impact on your coffee’s overall flavor profile, meaning you can ostensibly get two very different products from the same bean, even when utilizing the same roast. However, while this popular drink is sure to increase foot traffic in your café, it doesn’t come without its challenges. If you’ve found yourself asking “how long does cold brew last?”, we’re here to help! Evan Kluender gives insight into the science of oxidation, keeping your cold brew tasting fresh, and improving your brew’s quality. Plus, he shares a recipe for the cold brew he makes for the RNY office!
Please note that this article exclusively refers to traditional immersion cold brewing.
Introduction
Over the years, we’ve published a variety of articles about the growing popularity of cold brew. It’s gone from rising trend to café staple, and for good reason! That being said, keeping your cold brew tasting fresh can be challenging. While there are clearly defined FDA guidelines on food spoilage regarding coffee, there is also a period of time between making your first batch and it spoiling where it can lose its luster. Though we can’t give you the cure for food spoilage, we can give you some tips on preserving your cold brew’s freshness.
Why does coffee spoil?
A great place to start is understanding why coffee stales and eventually spoils. First, let’s take a step back into high school chemistry. You’re likely familiar with the concept of oxidation—it’s what causes a freshly cut apple to turn brown or a copper penny to turn green over time. Although the actual process of oxidation is complex, we can break it down to the essentials. Oxygen is a negatively charged, or electronegative, element. This means that it tends to steal electrons from other elements and compounds, damaging the compounds it’s stolen from and turning electrons into what are known as free radicals. It’s important to note that there are some reactions that can cause oxidation even without the presence of oxygen. However, air oxidation is the primary culprit of coffee going bad, so that will be our main focus.
While the effects of oxidation are obvious in the later stages, the process actually begins the moment a substance comes into contact with oxygen. To put it simply: oxygen causes molecular breakdown, meaning that the chemical compounds making up your coffee will eventually decay. Moreover, the compounds that are most susceptible to oxidation are those found in fatty acids. Generally speaking, higher quality coffees contain a higher concentration of fatty acids, which is bad news for those of us working with specialty grade coffee.
Cold Brew & Oxidation
Thankfully, there are a few aspects of cold brew that help slow down the process of oxidation, the first being right in the name. Cold brew is stored and served cold, and the reactions that cause oxidation love heat. This is why a pot of coffee becomes stale after about an hour and is questionable to consume from a food safety perspective after 4-5 hours at room temp. Because the fatty acids in coffee don’t extract as easily into cold water as they do into hot, you end up with much less oil in your coffee. As a result, your product keeps a little longer.
Additionally, coffee is naturally loaded with antioxidants, which (as the name implies) are a great defense against oxidation! An antioxidant is an element or compound with a positive charge, so it can give an electron to an element or compound that is missing one. This essentially reverses what oxidation does and slows down the process as a whole.
So, how long does cold brew last?
Since spoilage is unavoidable, our goal is to preserve coffee freshness until spoilage occurs. There are several steps you can take to improve the quality of your cold brew throughout its lifespan. Most of these steps are about keeping oxygen away from your coffee, which likely seems obvious if you’ve made it this far! You can keep your cold brew fresh in the following ways:
Brew Temperature
Despite its name, cold brew isn’t always brewed cold. While hot blooming or brewing at room temperature can produce a desired flavor profile, it can also accelerate oxidation and lead to a shorter shelf life. If your cold brew is staling faster than expected, try brewing it cold from beginning to end. Adjust your recipe or brew time to account for the temperature change and slower extraction time. At the end of this article, we’ve included a recipe that works great for brewing at cold temperatures!
Proper Storage
When you make a batch of cold brew, it’s best to store it in an airtight container and fill the vessel as much as possible. By leaving little room for air to sit on top, you reduce the amount of oxygen coming in contact with your coffee and keep it fresher longer. This generally has a marginal impact, but every bit helps!
Furthermore, storing your cold brew in a dark space and/or solid vessel prevents sunlight from affecting it. Coffee contains photosensitizers like riboflavin (vitamin B2) that become excited by ultraviolet rays and release electrons as a result. This can produce free radicals or even allow different compounds to bond, creating off-tasting flavors. Known as photooxidation, this kind of oxidation is what causes beer in glass bottles to become ‘skunked’ when left in the sun.
Nitrogen
Nowadays you see “nitro cold brew” everywhere, and it’s largely touted as a great way to give your cold brew a creamier mouthfeel. While that is absolutely true, it also doubles as an effective preservative to coffee! Nitrogen is much denser than oxygen, so filling a confined space with nitrogen displaces the oxygen in that space and forces it out. Therefore, if you have the ability to nitro infuse your coffee, you can remove oxygen from the equation and slow down oxidation. This essentially accomplishes the same goal as storing your cold brew in an airtight container and filling it to the top before sealing, but it’s much more effective.
Nitrogen infusing is typically done in a keg and dispensed from a tap in a café or from a can for cold chain RTD products. If you nitro infuse your cold brew, you’re also storing it cold and in a solid container blocking out light, making it the most effective method of cold brewing.
Our RNY Cold Brew Recipe
We used RNY # 55794 Brazil Natural Legender “Sitio Amoreira” for this recipe. You can use this recipe with any of our Brazil Natural Legender Especial offerings and achieve a similar result! That being said, this particular lot from Sitio Amoreira showcases sweet cherry top notes that we feel complement the brew style well.
1. Measure: You’ll want a 1:9 ratio – 1 part coffee (grams) and 9 parts water (milliliters).
2. Grind: Use a coarse setting to grind your coffee. We grind ours on an 11 using a Malkonig EK-43.
3. Submerge: Immerse your coffee in cold water, ideally as close to your brewing temperature as possible. It’s okay if the temperatures don’t match exactly; you just want to limit how long your cold brew spends in warmer temperatures. We brewed ours in a Toddy with a brew bag.
4. Refrigerate: Set your coffee aside and refrigerate for 17 hours. We brewed ours at 40°F for this recipe.
5. Strain and serve!
Shop RNY # 55794 Brazil Natural Legender “Sitio Amoreira”
This recipe tastes best on nitro but can be enjoyed with or without! As always, we are happy to help answer any coffee- or cold brew-related questions to the best of our ability. Also, stay tuned for our Spring 2024 recommendations for cold brew tea!
