Dear Eric,
Interesting question.
First, platinum is a catalyst, but that doesn't mean that it catalyzes every chemical reaction. It is most often used to catalyze chemical reactions involving hydrocarbon compounds, which are compounds composed of only hydrogen and carbon. This is why it is used in the petroleum industry and in the catalytic converters on cars. PtO2, platinum oxide, is also used as a catalyst to add hydrogen to unsaturated vegetable oils; vegetable oils are not hydrocarbons but the catalysis is still on a hydrocarbon part of the molecule. So from what I can read most of the catalytic action of Pt is on carbon-hydrogen bonds.
Browning in food is due to three main chemical processes: enzymatic browning, caramelization, and the famous Maillard reaction. Enzymatic browning is what causes a fruit to turn brown but that's not the kind of browning you're thinking about. (Side note: enzymes are natural catalysts that are protein molecules.) Caramelization is the thermal decomposition of sugar. The Maillard reaction is a reaction between specific kinds of sugars and amino acids (the building blocks of proteins). I think you are thinking about the Maillard reaction. The reaction is a nitrogen interacting with a carbon that is doubly bonded to an oxygen - completely different from hydrocarbon. I was not able to find any references for Pt catalyzing a reaction between a sugar and an amino acid (protein).
From the Wikipedia article on the Maillard reaction:
"The reaction is a form of non-enzymatic browning which typically proceeds rapidly from around 140 to 165 °C (280 to 330 °F). Many recipes call for an oven temperature high enough to ensure that a Maillard reaction occurs.[3] At higher temperatures, caramelization (the browning of sugars, a distinct process) and subsequently pyrolysis (final breakdown leading to burning) become more pronounced."
Although most people associate catalysts with "speeding up" a reaction often the effect of a catalyst is to make a reaction take place at a lower temperature than it usually does. You can think of a reaction as needing a certain amount of energy and a higher temperature means there is more thermal energy available for a reaction. A catalyst usually acts to orient the molecules in a reaction to a more advantageous arrangement - bringing them closer together or in a better orientation - so that the reaction basically takes less energy. IF (and it's a big "if") Pt could catalyze the reaction it's likely the speed would come from the browning reaction starting sooner at a lower temperature. In the case of cooking food I'm not sure you'd want to cook your food at a lower temperature -if the browning took place at lower temperature and faster the inner part of the food would not be cooked to the same degree because only the surface reactions would be catalyzed. There are more reactions that contribute to food taste and texture than just the browning reaction that might not happen at a lower temperature, and in the case of meat there's also a safety concern about lower temperature cooking.
If you were to coat a pan with Pt you would also not be oiling the pan. Your point about good contact is right - but there would have to be good contact between the food and the catalytic surface. Oiling the pan would impose a barrier layer between the catalyst and the food. The Pt (if it were effective) would end up catalyzing any reactions in the oil itself rather than the food you were trying to cook.
Lastly, the cost of Pt applied to a kitchen utensil would probably be prohibitively expensive. Pt is about $780 per ounce. You don't need a huge amount of catalyst but it needs to be in very fine particles and uniformly distributed over the whole surface. For comparison, the working part of a catalytic converter (the "honeycomb") weighs about 4 lbs or about 1800 grams. They contain about 3-7 grams of Pt. That means about 0.2% Pt at the lowest. If a 7 inch fry pan is about a pound in weight, subtracting weight for the outer surface and handle so the surface weight is about 0.5 pounds, rounding to 230 grams would mean you need 0.4 grams of Pt or 0.014 ounce or $11 of Pt for the pan. This effectively doubles the price of the pan if it even works.
All of this ignores also any safety concerns about Pt in contact with food. In general Pt is pretty inert and therefore pretty safe but it is still a heavy metal and you have to be concerned about its use with food.
What was your thought process behind trying to speed up the browning process? There may be better ways to go about it than catalysis.
Hope this answers this question.
Regards,
Karen
