Janet D. Stemwedel (whose nom de blog is Dr. Free-Ride) is an associate professor of philosophy at San Jose State University. Before becoming a philosopher, she earned a Ph.D. in physical chemistry. Email her at dr.freeride@gmail.com.
Finally we had a weekend day (and evening) with no rain. So, my better half got me a new bag of mesquite charcoal, I took the wire brush to the Weber, and I officially greeted Spring by grilling our dinner.
Of course, while you're tending the grill, your mind sometimes wanders, and you end up pondering (possibly geeky) questions. Such as:
- Does grilling vegetables (or tofu) create the same kind of carcinogenic compounds that are created by grilling meat?
- If so, given that eating lots of vegetables is supposed to reduce one's cancer risk, is it a wash?
- Or, is there an optimal volume-to-surface-area ratio that will maximize grilled deliciousness while minimizing effective carcinogens (and will that ratio doom me to parboiling before grilling)?
- Why is it that, when grilled, halloumi (a Cypriot sheep's milk cheese) does not melt? (It browns instead.)
- Does the process of cheese-making leave the DNA of the milk from which the cheese was made sufficiently intact that you could determine that it's really from a sheep (as opposed to, say, a gorilla)?
- No one would actually go to the trouble of milking a gorilla in order to make gorilla cheese, right?
Anyway, the weather was glorious (and the meal was well-received). And it sounds like there may be another storm by tomorrow night.
Comments
No one would actually go to the trouble of milking a gorilla in order to make gorilla cheese, right?
Keep hoping. You know if there is a stupid thing that can be done, some human somewhere will do it.
Posted by: coturnix | April 8, 2006 11:49 PM
The amount of source DNA in milk is probably negligible, being present only in contaminating epithelial cells. Most, if not all, of these would lyse during processing, leaving the DNA (a fairly labile molecule) exposed to the elements, as it were. On top of that, you have a relatively enormous amount of contaminating bacterial DNA.
My guess: you could use PCR to determine the source of fresh milk, but not cheese.
Posted by: Bill Hooker | April 9, 2006 12:47 AM
Oh, and my guess about halloumi is that it has a very high protein content, and something about the odd way it's made makes the protein matrix particularly heat-stable.
Posted by: Bill Hooker | April 9, 2006 12:57 AM
Mmm... asparagus in butter, wrapped in tin foil on a grill... yummy without the carcinogenic black bits!
Posted by: pough | April 9, 2006 1:45 AM
The question about halloumi is a common one (I've seen it in New Scientist). Wikipedia says that "the resistance to melting comes from the fresh curd being heated before being shaped and placed in brine." I'd be interested to know what effect this has on the structure of the cheese compared to other cheeses.
Posted by: Thomas Winwood | April 9, 2006 3:47 AM
coturnix says:
Taking it one step further...humans milk themselves, using a breast-pump, or so I've heard. Could not this milk be turned into cheese? Or butter?
Ewwwwwwwww!! :)
Posted by: Dave S. | April 9, 2006 9:43 AM
Several Mexican cheeses also do not really melt, including queso fresco and queso panela. And don't forget paneer. I'm not aware of any of these being processed the same as halloumi. I don't know how they will stand up on the grill, but they don't do the quesadilla thing.
So maybe the scienticians need to differentiate or come up with an alternate theory.
Posted by: Unlearned Hand | April 9, 2006 10:14 AM
As for the carnicogen vegetable question, this is what I've heard (but I haven't done the googling to find authoritative data for it):
Anything that is black, ie char, on grilled things==carcinogenic bad. However, I've heard that the char from vegetables is not as bad as that from say, red meat. Something about the different protein structures and what not. I would hazard a guess that grilled vegetables still have a net benefit in terms of cancer effects.
It's a good question though, and maybe I should actually go find good sources about this. I might be back later (quite a bit later) if no one else has real info.
Posted by: Kristin | April 9, 2006 4:46 PM
It appears that when grilling meats, or even searing them, the high temperatures can break down the amino acid creatine, which creates heterocyclic amines (HCA's). These amines have been linked to increased cancer in lab animals. Since vegetables don't contain creatine, they don't form the heterocyclic amines, and therefore aren't going to be carcinogenic when grilled. Here are a few sites I quickly found, which have tips for reducing your risk even if you like to consume high-temperature cooked meat:
http://www.cancer.org/docroot/PED/content/PED_11_1_Harmful_Chemicals_in_Grilled_Meats.asp
http://www.usaweekend.com/food/carper_archive/950625eat_smart_roasting.html
It's interesting to me that drinking tea and eating garlic with the grilled meat can help block the HCA's. Adding soy protein (1/2 cup of soy protein to 1 pound meat) can also apparently prevent the formation of 95% of the HCA's. Other tips - don't eat the blackened parts.
Anyway - it looks like veggies are fine.
Posted by: Kristin | April 9, 2006 10:14 PM
Hey food chemistry questions. Oh it must be that time of year for me to dust off my grilling causes cancer notes. I'm getting all excited. These carcinogens are formed by the reaction I study, the Maillard reaction.
There has been no reports of carcinogens formed on veggies or tofu (sorry, Kristen) and even the ones found on meat are present in small amounts. Also any kind of marinade will reduce their formation. You don't even need to parboil. I can find references on the cancinogens if any one is really interested or perhaps I should do a blog entry on this now that the weather has warmed up.
I once heard one of the researchers who studies this say that he grills at least three times a week.
Keep eating those veggies, grilled or otherwise. Some of the antioxidants will be intact after cooking.
As for the cheese question, I don't know about the survival of DNA but I think you could identify between sheep and gorilla milk by looking at the protein content. Different milks have different casein ratios and each mammal's casein has a slightly different amino acid profile.
BTW cheese doesn't melt as it isn't turning from a solid to a liquid but is a solid which, on heating, becomes less viscous and starts to flow. If I remember correctly, it is to do with the maturity of the cheese and the effect of aging on the protein structure. I'll have to get back to you on the details. But the reason why mature cheddar is crumbly and mozzarella stringy is to do with the protein network as well as the moisture content.
Posted by: Lab Cat | April 9, 2006 10:51 PM
I'm relieved to learn that I'm (probably) not harming my family with my grilling obsession (since it's a strictly vegetables/tofu/cheese/bread products grill -- just how I roll). For what it's worth, the parboiling I do is to make sure things cook all the way through (rather than being nicely charred on the exterior and raw in the interior).
On the other hand, I'm more concerned than I probably should be that, once it's cheese, the milk-of-origin from which the cheese was made may not be identifiable. I understand that this is my issue to work through, though.
Posted by: Janet D. Stemwedel | April 9, 2006 11:22 PM
Lab Cat's right, and I'm a idjit. If the protein survives well enough to be sequenceable by mass spec, you could fingerprint species by casein sequence or casein/other protein ratios; if not, overall amino acid profile would probably still be good enough.
Posted by: Bill Hooker | April 11, 2006 3:50 AM