Fermentation Support Forum

I make yogurt from Straus Family creamery organic milk (SF Bay Area), and I strain out some of the whey to make it thicker - like Greek-style yogurt. I use the whey instead of water to make sourdough bread (I understand it aids in rising as well as nutrition). My question is, how long does whey last in the refrigerator? How do we know when its too old to use?
All thoughts, scientific or not, are welcome.

I don't have any experience with whey except for powdered whey protein which is different so cannot really help with how long fresh whey would last in the fridge.

I react badly to it so no longer use it.

It will depend on the yogurt and how high you heated your milk and for how long. Albumin and lactose will be in the whey and how much of that will affect the longevity. With mine I don't heat my milk so it'll be good for as long as my yogurt is good. I think a good rule is to expect the same time frame as the yogurt itself and you shouldn't have to worry. But if you want to keep it longer I would suggest freezing it. I think it's a matter of peace of mind I just hate the "questioning yourself ritual" (smelling, licking, gambling should I use it?? Should I not??) and always wary/worried after you actually consumed it lol. So in order to NOT go through all that I just make sure I use it up as the same time frame as my yogurt or just freeze it right away

Sadly, whey does not last long. The bacteria die off within a few weeks. There are methods to extend the life of the bacteria in whey, such as adding molasses to it, such as when gardeners use whey to make lacto serum but you're better off using it up in a few weeks...

https://www.youtube.com/watch?v=OeR6HlxGo3I