Yeast starters can be a helpful tool in brewing, but they are not always necessary. Whether or not you need to make a yeast starter depends on a few factors, such as the starting gravity of your beer and the size of your yeast pitch.
When brewing a beer with a low starting gravity, typically under around 1.040, a yeast starter may not be required. This is because the yeast can easily ferment the sugars in the wort without needing a large population of yeast cells. In this case, pitching the yeast directly into the fermenter without a starter can be sufficient.
However, it's important to note that even though a starter may not be necessary, it can still be beneficial. Making a yeast starter allows you to increase the number of yeast cells available for fermentation, which can result in a faster and more vigorous fermentation. It can also help ensure that your yeast is healthy and active, which is particularly important if you are using older or stressed yeast.
In situations where you have a higher starting gravity, such as with a big, malty beer, making a yeast starter becomes more important. This is because a higher gravity wort contains more sugars for the yeast to ferment, and a larger yeast population is needed to effectively ferment these sugars within a reasonable timeframe. Pitching a normal pack or vial of yeast directly into a high gravity wort may result in a slow or stuck fermentation, as the yeast may struggle to keep up with the sugar load.
Additionally, making a yeast starter can also be beneficial if you are using liquid yeast, as opposed to dry yeast. Liquid yeast packs have a lower cell count compared to dry yeast, and making a starter can help increase the yeast cell count to ensure a healthy and robust fermentation.
In my personal brewing experience, I have found that making a yeast starter is often beneficial, even for beers with lower starting gravities. It gives me peace of mind knowing that I have a healthy and active yeast population ready to ferment my beer. I have also noticed that when I do make starters, my fermentations tend to be more consistent and complete. The beer finishes with a cleaner flavor profile and I have fewer issues with off-flavors or stuck fermentations.
While yeast starters may not always be necessary, they can be a valuable tool in ensuring a healthy and complete fermentation. If you are brewing a beer with a low starting gravity, under around 1.040, you may not need a starter, although making one can still be beneficial. However, for higher gravity beers or when using liquid yeast, making a yeast starter is highly recommended to ensure a strong and healthy fermentation.