Veal stock is lauded as culinary gold in French cooking, chicken feet are common in Chinese stocks, and pig feet are the secret weapon to many pots of split pea soup. What do all of these culinary weapons have in common? When cooked for a long time, they release lots of gelatin.
Hervé This in Molecular Gastronomy discusses the affects of gelatin on volatile odorant molecules:
“Cooks can slow down the evaporation of volatile molecules by putting them in the presence of larger molecules, with which they bond…. More general, in water solution, the amylose warps around hydrophobic molecules, many of which are odorant molecules….Gelatin does the same thing, hence its usefulness in sauces.”
“In the mouth these molecules are released in different ways, so that the flavor…lasts longer.”
In other words, gelatin makes meat stocks taste so good because it traps the flavor that might otherwise escape into the air while cooking.
After reading this I began to wonder; if gelatin traps flavor molecules, and we cook meat stocks for a long time in order to get the gelatin out of the bones, then why can’t we just add gelatin to the stock at the beginning? After all, gelatin is available in powdered and sheet form, and is used all the time in desserts and haute cuisine. I sat on this idea for a while, then decided it was time to try it out. I needed a liquid food that would otherwise contain no gelatin, was flavorful and contained lots of volatile aromatic compounds, and ideally doesn’t take very long to make. I decided that vegetable stock would suit the bill perfectly: it contains no gelatin, is packed with volatile flavor molecules, and doesn’t take much more than an hour to make.
So I began my experiment with gelatin.
- chopped onions, 673 grams
- chopped carrots, 352 grams
- chopped celery, 352 grams
- slices mushrooms, 273 grams
- chopped garlic, 35 grams
- black peppercorns, 20 whole
- parsley, 3 grams
- thyme, 3 grams
- rosemary, 3 grams
- water, 2648 grams
- gelatin, 13 grams
- Divide all materials, except gelatin, evenly among 2 pots, reserving some water from one of the pots.
- Heat the reserved water in the microwave until boiling, then stir in the gelatin. Add the dissolved gelatin to the pot, stirring thoroughly.
- Cover both pots and heat over medium heat until simmering. Monitor closely.
- When both pots are simmering, reduce the heat to maintain a medium simmer.
- Cook for 1 hour, stirring every 10-15 minutes.
- Remove the pots from heat and let sit for 30 minutes.
- Strain pots into separate containers.
- Let cool.
Conclusion and Discussion:
As in bakers percentages, I choose to use a 1% gelatin solution based on the total weight of the water. This resulted in a partially-set stock when refrigerated: it wasn’t scoop-able, but was very gloopy when poured.
The results of this experiment were both surprising, and predictable. During cooking, there was a significant difference between the way each pot smelled. The pot without gelatin smelled great: sweet from the onion and carrots, heady from the garlic and mushroom, bright and vegetal from the celery, with hints of thyme, rosemary, and parsley. Exactly like a pot of vegetable stock should smell. The pot with the gelatin smelled like… very little. Near the end of the cooking, it began to smell like celery, but the aromas were very muted the entire time. Let’s just say that Christine wouldn’t know what it was. ;)
Upon tasting, as I’m sure you can guess, the gelatin-free stock tasted much better. It had a brighter flavor, and tasted very similar to the way it smelled: sweet, bright, a little vegetal. The gelatin-added stock still tasted good, but its flavor was muted and lacked the brightness that I was hoping for. However, the flavor of the gelatin-added stock did last longer in the mouth, as was to be expected.
Since the first tasting was at room temperature and without any salt, I included both in the second tasting. Samples of both stocks were warmed in the microwave, and a tiny pinch of salt was added to each. Tasting revealed that the flavor of both stocks improved, but the difference in flavor and length-of-flavor stayed the same. The final test was the addition of lemon juice, as an acidic ingredient to try and add a brighter flavor to the gelatin-added stock, in addition to heat and salt. While the lemon juice did slightly brighten the flavor of the gelatin-added stock, it didn’t take much lemon juice for the flavor to become the predominant one.
Adding gelatin to a liquid at the beginning of cooking does indeed function to prolong the flavor of the liquid in the mouth, however it has also traps and fails to release some of the brighter flavors from aromatic vegetables. While adding gelatin to flavorful liquid that contains large quantities of aromatic molecules (i.e. “bright” flavors) may produce undesirable results, it may be useful to prolong already muted flavors, or to alter the flavor of a dish.
It might also be useful to use gelatin in smaller percentages than were used in this experiment. Percentages of 0.5%, 0.25%, or even 0.01% may achieve a balance between trapping aromatic molecules during cooking, while releasing them more quickly in the mouth.
Sorry for the lack of photographic evidence.