As an expert sommelier and brewer, I can say that flavor concentrates do not technically expire or become unsafe to use. However, they can undergo changes over time that may affect their taste and quality. This is why the process of steeping is often recommended for e-liquid recipes.
When it comes to flavor concentrates, it's important to understand that they are made up of various volatile compounds that give them their distinct flavors. These compounds can interact with each other and with the base liquid over time, leading to changes in taste, aroma, and overall quality.
One common change that can occur in flavor concentrates is a loss of potency. Over time, the volatile compounds that give the concentrate its flavor can evaporate or degrade, resulting in a weaker flavor profile. This can be especially noticeable in more delicate flavors such as fruits or herbs.
Additionally, some flavor concentrates may develop off-flavors or become “perfumey” if they are not stored properly or for too long. Exposure to heat, light, and air can accelerate the degradation process and lead to undesirable changes in taste. It's important to store flavor concentrates in a cool, dark place and tightly sealed to minimize these effects.
However, it's worth noting that not all flavor concentrates undergo significant changes with time. Some flavors, particularly those with stronger or more stable compounds, may remain relatively unchanged even after an extended period. It's always a good idea to check the manufacturer's recommendations for each specific flavor concentrate to get a better understanding of its shelf life and potential changes.
In my personal experience, I have used flavor concentrates that were past their recommended expiration dates without any noticeable negative effects. However, I did notice that the flavors were not as vibrant or potent as when they were fresh. This is why steeping is often recommended, as it allows the flavors to meld together and develop fully, even if they have undergone some changes.
While it is generally safe to use expired flavor concentrates, they may not provide the same level of flavor and quality as fresh ones. It is always advisable to check the manufacturer's recommendations and store the concentrates properly to minimize any potential degradation. Steeping can help enhance the flavors and compensate for any changes that may have occurred.