How do I choose coffee for a cold brew bag?

Choosing coffee for a cold brew bag involves balancing extraction time with flavor profile. Since cold brew bags are effectively large tea bags for coffee, they are designed to be convenient. However, convenience shouldn't come at the cost of the final flavor. Because the coffee remains in contact with water for an extended period, the roast level and the physical grind of the bean are paramount.

Medium and dark roasts are generally superior for cold brew bags. These roasts are more soluble and contain the deep, rich flavor compounds like chocolate, caramel, and molasses that cold extraction highlights. Light roasts, while delicious in hot brewing, often result in a thin, sour, or overly acidic concentrate when brewed cold, which is rarely what consumers want when making a batch of cold brew for the week.

The grind size is perhaps even more important than the roast. If you are grinding your own coffee to put into a bag, ensure it is a very coarse grind—similar to sea salt. If the grounds are too fine, they will not only create a gritty, silty mouthfeel but also release too many bitter compounds during the long steep. The bag serves as the filter, so a coarse grind helps prevent "stewing" the coffee and keeps the concentrate clean and sweet.

When you are buying coffee for this method, freshness still matters, but it is not as critical as it is for espresso or pour-over. You can use coffee that is a few weeks past its roast date, provided it has been stored properly. Look for bags that emphasize "chocolatey," "nutty," or "full-bodied" descriptors. These flavor notes tend to be the most resilient during the slow, cold extraction process.

In practice, using a cold brew bag is about simplicity. By choosing a high-quality medium-dark roast and grinding it coarsely, you create a baseline concentrate that is incredibly versatile. Whether you mix it with ice, water, or dairy, you'll have a consistent, low-acid coffee base that makes mornings significantly easier.