Is there a scientific or food industry term for what makes a water solution behave like a detergent, and perhaps an associated unit of measure?
For example, the pH of a solution measures its acidity; is there a similar term for "soapiness"?
What property makes a liquid soapy/bubbly
food-sciencewater
Related Solutions
IMO, this really would have greater lasting value with a single detailed answer instead of a poll. Here's an annotated list of all the recommendations so far:
On Food And Cooking (Harold McGee) is all science at a very detailed level, combining food chemistry and biology and explaining the interactions between ingredients and the mechanisms behind various cooking methods. If you're looking for a pure science book, this is it.
Good Eats: The Early Years and Good Eats 2: The Middle Years by Alton Brown. His books are less technical/scientific than other authors and tend to focus more on application, making them more accessible to less hardcore cooks.
CookWise (Shirley O. Corriher). Written by a biochemist who has done a lot of consulting in the food industry. This is more practical than McGee and more technical than Alton's books. It also includes a ton of recipes, which can be a good thing or bad thing depending on your personal preferences. She has also written a baking version, BakeWise.
Molecular Gastronomy (Hervé This, translated by Malcolm DeBevoise). This is more of a niche book (about - surprise - Molecular Gastronomy) and as you might expect is a little French-centric. What's really great about this book is how it debunks a lot of popular cooking myths with actual controlled experiments and hard data. It wouldn't be my first choice to recommend to a Food Science newbie, but nevertheless a good one to add to your collection.
The Fat Duck Cookbook (Heston Blumenthal). Written by the founder of the Fat Duck Restaurant in the UK. It's about the history of the Fat Duck and has a big recipe collection (from the restaurant, obviously) and a section at the end dedicated to food science. This one's really for the advanced crowd as it involves a lot of molecular gastronomy, sous-vide and other esoterica - complex preparations, hard-to-find ingredients and unusual/expensive equipment.
Cooking for Geeks (Jeff Potter) is, as the title implies, written to appeal to geeks, and as such has a certain amount of science but tends to be quite a bit more basic as far as actual cooking technique goes. It's more "applied science." Honestly, I wouldn't recommend this for very experienced cooks, but it's great for getting into cooking and gaining an enthusiasm for it (if you're kind of a geek).
Cooking for Engineers is a web site, not a book, which has the obvious advantage of being free and searchable. It's hard to really define this as its scope is so wide, but I will say that I've found it to be a surprisingly useful and detailed resource whenever I need to find out something quickly.
What Einstein Told His Cook (Robert L. Wolke) is also mostly on the science itself but is written to be more accessible to the layperson. As one reviewer on Amazon put it, Wolke is like the Bill Nye of Food Science. One part science, two parts entertainment. Another member has criticized it for making unproven claims (particularly on nutrition).
The Cooks Illustrated annuals (from America's Test Kitchen) are less about the actual chemistry of food but do highlight a very scientific approach to cooking based on up-front research, experimentation and testing. See David LeBauer's Answer for a more detailed explanation.
The Science of Cooking (Peter Barham) focuses on the chemistry and physics of why some recipes work and some fail.
khymos.org - on the surface it's about molecular gastronomy, but you'll find much of the science of cooking (e.g. the chemistry behind "working" flavour pairings etc) on there too.
The Food Lab: Better Home Cooking Through Science (J. Kenji López-Alt) is a collection of detailed recipes, tips and explanations. It's written to be easily accessible to a chef without much experience.
Serious Eats is a website with both recipes and stories about how the recipes were developed (often with pictures of various attempts to compare how changing processes or ingredients affected things). Especially see the 'techniques' section of The Food Lab
I don't remember the exact science behind the potatoes not turning to mush ... I know it was discussed on an episode of America's Test Kitchen, and they even discussed the amount of vinegar and how it affected the window for cooking times. (I want to say it was on an episode where they were making an Austrian potato salad)
... and it's not specifically vinegar, and not solely potatoes. Acids will stop quite a few items from softening when cooking. I know the list inclues onions (pre-cook onions before adding acids if you want them to disolve into a sauce), potatoes, apples ... I'm guessing there's others.
For potatoes and apples, most recipes claim it's to slow down browning. You see it in potato salad, but not mashed potatoes. You'll see it in apple pies, but not in applesauce ... because they'll come out lumpy.
Matt already mentioned three uses for vingear:
- as half of a chemical leavener
- tenderizing / marinades
- preservation / picking
- coagulation (eg, when poaching eggs)
But also :
- stabalizing eggwhite foams (might just be a variation of coagulation?)
- denaturing / "cooking" (eg. in the case of ceviche; a variation of marinating?)
- flavor (might not be a 'science case' ... but sour is one of the primary tastes; especially helps to balance out fatty dishes)
- cleaning / disinfection (might not be a 'cooking' use)
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Best Answer
Since I could see this being a cooking/food science question if you really wanted to play with this property of liquids in drinks, perhaps a quick answer is in order. This really would be quite well-suited to the physics stackexchange, though - this is a concept that's quite describable by physics.
To follow up on Sobachatina's comment, the property you're in fact looking for is surface tension (which is reduced by surfactants like detergent). If you want to compare liquids, be they water, water+detergent, milk (water+stuff), or even alcohol or oil, you just want to compare their surface tensions.
Surface tension is in fact a measurable quantity, with dimensions of force per length. There are a couple of equivalent definitions:
when increasing the area of the surface by a small amount, the amount of work (energy) required per area increase; or
when the surface is bounded by a line (imagine a bubble film and string), the amount of force on that line per length.
You should note that surface tension depends on the fluids on both sides of the surface. Most commonly we talk about surface tension of an arbitrary liquid against air, but surface tension against glass, plastic, or metal is commonly visible in your vessels and utensils, and surface tension between various fluids is of course visible when you try something like mixing oil and water.
As for actual examples, Wikipedia has a short data table with surface tensions of various fluids against air. Among them are a few potentially relevant for cooking: acetic acid + water (though stronger than normal vinegar), ethanol + water, a very concentrated sucrose solution, and water. Note that the addition of alcohol or acetic acid substantially reduces surface tension of water!
If anyone can follow up with more data on surface tension of liquids commonly seen in cooking, I'd be very interested!
It's also possible to measure surface tension at home, though I've never done it, and I'm not sure how accurate you could get.