MacGruff - for a second there I thought like Tomer that your cheese was too acidified. I went back to your original message to see if you have any texture or melting comments and see how you made it. Typically an acidic cheese will be hard, crumbly, chalky and won't melt. I do not see that you mentioned any of that but one thing did pop up that left me like "
...that recipe said what?
"
Let me get this right in case I misunderstood: Did your recipe say you can make Havarti and eat it the next day??? Are you sure??? This makes no sense at all whatsoever, not by a long shot. Which brings me to the subject of sour taste - this is very typical of un-aged cheese and I think that's all there's to it here.
This type of cheese needs a few days for the acidity to start climbing back up. It takes a while for it to turn yellow too. Further bacterial activity then begins to build rind flora, lactate buildup and lactose digestion, converting sugars and proteins to the gas that create the small eyes (holes) in Havarti. There is a long term enzymatic activity: proteolysis process (breakdown of proteins - this is what matures the cheese and gives it the texture) and Lipolysis (the breakdown of fatty acids which builds up the sharpness of its flavor). Yeasts build aromatic propertiesand gas. Other bacteria from your starter now enhances the flavors; Diacetyls for example make up buttery flavors, or Helveticus create nutty flavors Lipase can create bitterness and sharpness ...you get the idea. There is also succession effect, microorganisms convert one substance to another and the new substance kicks off a totally new bacteria with its own set of flavors, aroma and texture contribution. Then, there is the aspect of safety: These microorganisms outgrow pathogens and render a safer cheese that shouldn't spoil. In short, it's a microscopic garden and zoo in one; a little happening and lively ecosystem. Managing this craziness to your liking is the real art of cheesemaking. It's a patient process that takes weeks if not months. So, unless you are making yogurt, spreadable cheese or a flavorless lazy cheese (Paneer or Queso Fresco), arm yourself with an extra dose of patience, hope and sarcasm. It takes time and doesn't always work.
Your Havarti is probably a success. Just age it for a couple of months and resist temptation to try it until then. (I suppose now that you've tasted it you need to close it somehow. Can you vacuum it? Is it still fairly moist?)
As for your other problem with the cracking: This happens when a cheese loses too much moisture too quickly. Add moisture to the environment. Use an aging container for example to lock moist air inside. What's your cave humidity like? (again, vacuuming will resolve this issue). This could also happen if your cheese is bloating - is that happening? That happens usually due to contamination or fermented animal feed.
