When it comes to cold brew, its versatility appeals to a wide range of consumers. Brewing in cold water instead of hot can drastically alter your coffee’s flavor profile. However, while this popular drink can increase foot traffic in your café, it presents its challenges. If you’re wondering about the shelf life of cold brew, we’re here to help! Evan Kluender shares insights on the science of oxidation, maintaining freshness, and improving quality. Plus, he provides a recipe for the cold brew he makes for the RNY office!
Introduction Over the years, we’ve published articles about the growing popularity of cold brew. It has transformed from a rising trend to a café staple for good reason. However, keeping your cold brew tasting fresh can be challenging. While there are defined FDA guidelines on food spoilage regarding coffee, there is also a period when it can lose its freshness before spoiling. We can’t provide the cure for food spoilage, but we can offer tips to preserve your cold brew’s freshness.
Why Does Coffee Spoil? Understanding why coffee stales and eventually spoils is a good starting point. Let’s revisit high school chemistry. You’re likely familiar with 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 simplify it. Oxygen is a negatively charged element and tends to steal electrons from other elements and compounds, damaging them and creating free radicals. It’s important to note that some reactions 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 later stages, the process begins the moment a substance comes into contact with oxygen. In short, oxygen causes molecular breakdown, meaning the chemical compounds in your coffee will eventually decay. Furthermore, the compounds most susceptible to oxidation are fatty acids. Generally, higher quality coffees contain a higher concentration of fatty acids, which is bad news for those 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, starting with its 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 temperature. Because fatty acids 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. 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.
