another_jim wrote:I don't know how the GS3 steam boiler is set up stock; but if it is set to 1.8 to 2 bar like other LMs, then the tips may not work as designed if you reduce the pressure down to 1.4. In all likelihood, the tips will roil the milk and incorporate air when fully submerged at the factory set pressure..

Interesting.

The factory sets the GS/3 steam boiler pressure to 2.0 BAR. At that pressure, and with the stock tip, I guess it's possible just submerging the tip would work. I never tried that because, as a newbie, I had read countless instructions for proper steaming that said to stretch with the tip partly submerged and then sink the tip to incorporate the foam. I can honestly say that before Jim's post I have never heard of just sinking the tip.

Like many GS/3 owners, I wasn't able to steam well using the "standard" technique with the stock configuration, so I got the EPNW 4-hole tip (smaller holes than the stock tip) and lowered the pressure. That seems to work pretty well. Also, Nicholas recommended a somewhat longer steaming time to bring out more sweetness in the milk (15 seconds, as I recall.) I recently saw a post that said just the opposite (steam as quickly as possible).

Guess I have yet another espresso lab experiement to perform: go back to the stock tip and pressure and see if it works to sink the tip from the beginning, and see if the sweetness of the milk is affected. I'll also have to check whether using skim milk makes a difference to any of this.

BTW, the stock GS/3 comes with the no-burn wand, which may make it work somewhat differently than the LM commercial machines. I switched to the burn-me wand when I got the machine, so mine should behave more like its big brethren.

Milk proteins will denature and open from their coiled state into long strands by relaxing hydrogen bonds along its length. This allows them to become entangled with each other. This stabilizes the foam and increases viscosity. It's possible maillard reactions occur to the proteins as well adding complexity of flavor. Sweetness comes from hydrolysis of lactose into its constituent sugars (it's a disaccharide), galactose and glucose, which are sweeter than lactose.

What determines how fast/slow a steamer steams milk?

I have a bellman stovetop due to space restrictions, and it takes about 90-120s to get cold milk to 140F. I'd really love to get this under 60s...

Damn, after reading this thread I can no longer get decent microfoam on either of my machines! Ack, back to the drawing board.

I can't speak about the kinetics of the reactions taking place but I know there are a lot of variables to this problem. Protein denaturing can occur for a lot of reasons, some culinary examples include: Heat (Flan, cooked meat), pH (ceviche), Mechanical (meringue). Clearly there is a lot of mechanical agitation and heating due to hot steam and high shear rates at the tip. I also know that heating rate can cause different effects on protein. A slowly heated custard will set much lower in temperature than a fast one, you better know this if you want to make a good crème brule. I don't know much about hydrolysis of polysaccharides but it can be accomplished with temperature and assisted by acid (like making an invert sugar from sucrose). Interestingly, lactose can be hydrolyzed with bacteria (Lactobacillus acidophilus), this is why yogurt is tolerated by many with lactose intolerance. A rule of thumb is that reaction rates tend to double every 10 degrees C. Given the number of variables involved, I think an empirical study is warranted. We've all seen on HB what happens when too much science is thrown at a complex multivariate problem when all we care about is what's in the cup.

For what it's worth, I got a HUGE increase in micro foam by changing the wand tip from three hole to single hole. The single hole is slightly larger in diameter the holes in the three hole tip, but the steaming process is slower and creates less heat with lots more micro foam and far less big bubble foam. I use a Pavoni Pro.