How does one mix up the perfect cheese fondue? After studying how the ingredients interact with one another, scientists have found the dish is really a complex multiphase system caused by the flow behavior or rheology of the cheese, wine, and starches, which can make all the difference between a creamy meal and a gummy mess.
Renowned as the national dish of Switzerland and the inspiration for fondue sets that are given as wedding gifts with bewildering regularity, the cheese fondue is a familiar dinner entertaining standby. It was supposedly developed by Swiss peasants as a way to make old, hard cheese edible in the middle of winter, though some suggest this it was actually an urban invention with a bucolic tale attached to it by the Swiss Cheese Union. Nevertheless, it has gained worldwide popularity over the last century.
Whatever its origins, the cheese fondue seems to be a very simple dish to make. It's just a matter of mixing wine, a blend of cheeses, starch powder, and spices into a pot, stirring the mix together as it heats and melts, and then eating it by dipping bread chunks or other items into the sauce. Unfortunately, it's always possible to screw it up and the result is pot full of an unappetizing gummy, watery, or horribly separated ingredients.
By looking at the chemistry and mechanics of the fondue, a team of scientists from Zurich's Institute of Food Nutrition and Health have gained insights into how to make a perfect fondue with the right texture, flavor, mouthfeel, and bread clinginess. This is because, at its most basic, a cheese fondue is water with a dispersed mixture of fat droplets, caseins, and starch granules with the concentration and quality of the latter being of particular importance.
The idea, the scientists say, is to create a sauce that has just the right balance of viscosity. It has to be able to coat the bread, defy gravity, give the right feel in the mouth, and release its flavor without being too thick or too watery. In addition, the ingredients need to integrate with one another so the fondue doesn't curdle or separate.
Essentially, the cheese that goes into the fondue is a protein gel that encases globules of fat. As the cheese melts, the gel network shrinks and collapses, releasing the fats. Adding wine to make up 30 to 40 percent of the weight, especially if it's dry with a low pH, introduces both water and ethanol into the cheese, dispersing the proteins and emulsifying the fat globules. By adding a starch made from potatoes, maize, or carrageenan amounting to three percent of total weight prevents the proteins, water, and fats from separating. As it gelatinizes, the starch also increases the viscosity.
The tricky bit is to get the fondue to settle around the gel point. That is, the point where the viscosity is set to make a sudden change from liquid to solid. By balancing the various electrostatic forces of the ingredients, the right level of viscosity can be achieved.
What this boils down to in the caquelon is that by carefully balancing the ingredients, especially the wine, and using the most efficient starch, like carrageenan, it's possible to make a cheese fondue with just the right creaminess and even makes it more digestible.
As to what to do with the fondue set after it's been sitting on top of the dining room cabinet gathering dust for five years, that's another matter.
Source: ACS Omega (PDF)
