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This evening I attempted to make gjetost. I started with a gallon of milk and made mozzarella, then added a little dry milk, and made ricotta. Finally I was going to reduce the whey down into gjetost.

Once I got the whey reduced down to about 10% of its original volume, the simmering became incredibly... weird? Basically the bubbling became very erratic, and at least twice there was a sudden "BLUB" which sent showers of 230+ degree whey showering across the stovetop, also making a noticable SLAM when the pot physically jumped on the stovetop. After narrowly avoiding a bunch of burns twice, I moved the pot off the heat and walked away. I want to make the recipe but I'm not risking a trip to the hospital.

So, has anyone ever seen this happen? Why does it simmer so erratically and then have one big GLUB/bubble explosion in the center that is so violent? I've heard of things getting super heated, but that doesn't seem like it would apply here because it's not a completely pure liquid (there are some curds of albumin protein which would seem to be good origination sites).

  • If the temperature was in fact 230 (I infer F), then you have a very saturated solution of whey, which is probably pretty thick and gloopy. What kind of cheesevmaking uses employs temperatures of that level? – SAJ14SAJ Apr 7 '14 at 2:27
  • Gjetost essentially reduces all liquid out of whey until there is little left but caramelized albumin protein. It creates a fudgey, caramel-like cheese. biology.clc.uc.edu/fankhauser/cheese/Gjetost/Gjetost.htm – Matthew Apr 7 '14 at 2:29
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    Evidently you are making kitchen napalm, then. You want a much too big pan to keep it confined, and appropriate protective gear. You might look for welder's supply houses. – SAJ14SAJ Apr 7 '14 at 2:43
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    Yeah, I have decided to let this batch go. I made 2 more attempts, and each time it went off with enough force to take the lid off and spray all over my range, even at very low temperatures. I think this may require a large cheap non-aluminum pot that I don't care about. Between this and lutefisk, no wonder Scandanavians are so tough :) – Matthew Apr 7 '14 at 2:52
  • Have you tried a splatter guard? I know they're pretty good for tomato sauce, but I've never tried them at this heat. – vwiggins Apr 9 '14 at 12:27
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Reducing whey to that level of concentration is going to create what is very likely to be a viscous, non-newtonian fluid. That means its flow rate changes with sheer stress, much like ketchup does.

The heat at the bottom of the pan will slowly heat up water until a bubble of steam starts to form, and press against the remaining fluid. At first, the pressure will not be enough to overcome the viscosity of the.. substance. Eventually, the pressure will be sufficent that bubble ruptures, creating sheer in the fluid, which suddently becomes much mroe liquid. And so you have a giant gloop.

See related: Why does tomato sauce spatter more than other sauces?

  • That is EXACTLY what I witnessed, and the non-newtonian fluid created would explain the really erratic bubbling I saw! Thank you! – Matthew Apr 7 '14 at 2:49
  • Why not simply reduce the cooking temperature below that which steam forms? You don't have to boil to reduce. You could put it in a shallow pan in a 70C oven and perhaps get the result you want. – GdD Apr 7 '14 at 7:50
  • @GdD I suspect that at low temperatures, the cheese won't caramelize properly. – rumtscho Apr 7 '14 at 9:02
  • This was at a low simmer - we still had problems where it would bubble a little, stop, and then BAM, explosion. – Matthew Apr 10 '14 at 13:53

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